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Impact of Environmental Stressors on Hair

by james.runkle@drummondst.com james.runkle@drummondst.com No Comments

Physiochemical properties of hair are impacted by many stressors ranging from physical, chemical, mechanical to environmental. A combination of several environmental factors such as sun exposure and air pollution can impact overall hair and scalp health. Damage induced by these aggressors impacts hair properties such as protein content, melanin oxidation, surface quality and structural components [1]. Hair and scalp care go hand in hand and prolonged exposure to pollution can cause scalp sensitivity. In this article, we will discuss the impact of environmental factors on hair and some of the treatment strategies that can help protect hair against these harmful effects.

Hair Structure

Hair is composed of heavily melanized keratin fibers. Hair keratins are classified as hard keratins, consisting of 65-96% proteins, 1-9% lipids, 3% melanin and other minor compounds. These proteins are the building blocks that contribute to the strength, flexibility, and overall health of hair. Hair is broadly structured in three layers: the cuticle, cortex, and the medulla. The cuticle forms the outermost coat of the hair shaft, acts as a protective wall shielding the inner layers and contributes to the feel and appearance of hair. The cuticle is subjected to many day-to-day insults such as washing, brushing, the use of thermal tools, UV radiation and pollution. Thus, the hair structure is gradually damaged. Next, we will review the impact of UV exposure and air pollution on hair properties.

Impact of UV radiation

Both UVA and UVB components of sunlight radiation are responsible for inducing damage to hair. It has been reported that morphological damage to the hair is caused by UVB and chemical changes in hair are caused by UVA [2].

UVB radiation (280-315 nm) affects hair approximately 5 µm beneath the surface [3] and localizes primarily in the cuticle area. It attacks the melanin pigment and protein fractions of hair [4]. UVB range is more harmful than UVA for hair damage: once the main chromophore of hair proteins absorbs UVB, UVA acts as a secondary cause of damage [1]. Effects of UVB radiation can be severe, resulting in the breakdown of di-sulfide bonds, which are fundamental to hair structural integrity. Such disruptions impact hair’s mechanical properties, resulting in the loss of tensile strength, increase in porosity and irregularities on the hair surface [5].

UVA radiation (315-400 nm) is less energetic but due to its longer wavelength, is capable of penetrating cuticle layers and cortex (causing partial loss of lipid, protein, and melanin) [6]. However, UVA is primarily responsible for color changes in hair. In pigmented hair, melanin granules provide photoprotection to hair proteins and lipid components from oxidation. Therefore, blonde, and grey hair, which are low in melanin, are susceptible to more damage [7]. Red and dark-brown hairs photo yellow when exposed to near ultraviolet plus visible radiation [4].

Overall, prolonged exposure to UV radiation can cause a decrease in 18-methyleicosanoic acid (18-MEA), a fatty acid found on the surface of hair cuticles and photochemical degradation of cystine, tryptophan and tyrosine. These changes contribute to signs of damage such as increased surface friction, poor manageability, brittle hair, and loss of shine, color, and tensile strength.

Impact of Pollution

Air pollutants consist of complex and varying mixtures of different size and composition particles suspended in the air. These can be polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), nitrogen oxides (NOx), particulate matter (PM), ozone or cigarette smoke [8].

Particulate matter (PM) is classified into PM2.5 and PM10. Some PM2.5 particles form because of complex reactions between sulfur & nitrogen oxides and other compounds, which are pollutants emitted from power plants, industries, and automobiles [9]. PM10 particulates like dust and pollen are much larger in size.

PM binds to the hair surface and infiltrates the hair follicle, something which could affect hair growth and texture. Severe air pollution can alter the hair surface making it rough and dull. The presence of sebum on the hair surface favors the deposit of larger PM. When it comes to your scalp, long term effects of pollution can contribute to scalp irritation, itching, excessive sebum secretion, dandruff, pain in the hair roots and hair loss. The combination of these symptoms is defined as sensitive scalp syndrome [10]. Excessive sebum production on scalp translates into oily / greasy roots, clogged pores, and blocked hair follicles. This can lead to an effective weakening of the hair at the root, making it to more prone to breakage [11].

PAHs are among the most widespread organic pollutants and in addition to being a human health risk factor they can also damage hair [12]. PAHs cling to the hair surface and the oxidizing pollutants penetrate inside the hair fiber, causing chemical damage to hair cuticle and protein. Furthermore, they can cause oxidative stress to hair when exposed to UV radiation; It is also shown that damage to cuticle and cortex is higher when PAH contamination increases and indeed fibers with increased PAH contamination show increased damaged after UV treatment [13].

Product Solutions to Combat Environmental Stressors

Consumers are always looking for products that help protect hair and scalp from these external aggressors. According to Mintel (GNPD, 2021) there has been a 61% increase in hair care product launches in North America with anti-pollution claims in the past three years. As consumers are shifting to healthier lifestyles and making cleaner choices, ingredients, their sources, and functionality are determining their purchase behaviors.

Film formers, UV filters and certain antioxidants have been used in hair care products to help protect hair from UV damage and prevent color fade. However, there is a growing need for multifunctional ingredients whose benefits go beyond sun protection alone, extending to helping protect hair and scalp against pollution as well.

The use of gentle cleansing ingredients to wash hair without disrupting scalp homeostasis has been a huge focus area for consumers. Botanical options such as Moringa and Chia seeds along with food-inspired ingredients like turmeric and bioinspired molecules (amino acids) have been spotlighted as ones that help purify, detox, and soothe the scalp. Antioxidants and anti-inflammatory ingredients like apple cider vinegar and exfoliators such as pink salt are in demand and help to stimulate good blood circulation. They can also help to remove build-up and excess sebum on the scalp.

As the photo-pollution category continues to evolve, researchers are now conducting exposome studies that can reveal new hypotheses on how hair could be affected by daily life environment and routine using wearable devices [1]. The use of new data collecting devices and beauty apps continue to rise, as they help engage consumers and guide the cosmetic industry in developing new products and concepts.

Conclusion

Pollution and sun exposure are a global concern and the emphasis is beyond just skin. These stressors can cause hair damage and induce scalp sensitivity. Novel ingredients and new products that focus on providing full protection continue to advance. Key for hair and scalp health are protective hair and scalp care solutions that can help create an eco-barrier on the hair surface to prevent the adhesion and penetration of pollutants and radiation, restore hair from the inside-out and provide scalp bio balance.

References

  1. Rodrigo De Vecchi, Júlia da Silveira Carvalho Ripper, Daniel Roy, Lionel Breton, Alexandre Germano Marciano, Plínio Marcos Bernardo de Souza & Marcelo de Paula Corrêa, “ Using wearable devices for assessing the impacts of hair exposome in Brazil” , Scientific Reports ,volume 9, 13357 (2019)
  2. Kazuhisa Maeda, Jun Yamazaki, Nana Okita, Masami Shimotori, Kyouhei Igarashi and Taiga Sano, “Mechanism of Cuticle Hole Development in Human Hair Due to UV-Radiation Exposure”, Cosmetics, 24, 5(2) (2018)
  3. Lee, W. S.,” Hair photoaging “Aging hair, Springer, 123-133 (2010)
  4. Estibalitz Fernández, Blanca Martínez-Teipel, Ricard Armengol, Clara Barba, Luisa Coderch, “Efficacy of antioxidants in human hair”, Journal of Photochemistry and Photobiology B: Biology 117,146-156 (2012)
  5. Timothy Gao, Jung-Mei Tien, Abhijit Bidaye, Scott Cardinali and Jena Kinney, “A Diester to Protect Hair from Color Fade and Sun Damage”, Cosmetics & Toiletries (2013)
  6. Ernesta Malinauskyte; Samuel Gourion-Arsiquaud, “Dirty Air, Hair and Skin: Pollution Studies”, TRI talks
  7. Trefor A. Evans, “Combing Through Sun and Pollutant Effects on Hair”, Cosmetics & Toiletries (2016)
  8. Eleni Drakaki, Clio Dessinioti and Christina V. Antoniou, “Air pollution and the skin”, Frontiers in Environmental Science (2014)
  9. Seinfeld, J. H., & Pankow, J. F “Organic atmospheric particulate material”, Annual review of physical chemistry, 54(1), 121-140 (2003)
  10. Rajput R, “Understanding Hair Loss due to Air Pollution and the Approach to Management”, Hair Therapy and Transplantation (2015)
  11. Ashland: “How air pollution can turn into air pollution, and solutions to prevent it” Cosmetics design-europe.com (2019)
  12. Sharleen St. Surin-Lord, “Sun, Metals & Pollution Are Damaging Your Hair”, Happi (2020)
  13. Gregoire Naudin, Philippe Bastien, Sakina Mezzache, Erwann Trehu, Nasrine Bourokba, Brice Marc Rene Appenzeller, Jeremie Soeur and Thomas Bornschlogl, “Human Pollution exposure correlates with accelerated ultrastructural degradation of hair fibers”, PNAS, 116(37), 18410-18415(2019)

 


 

Mythili Nori has worked in the Personal Care industry for over a decade. Her expertise is in Product Claim Substantiation and Data Science. In her current role at BASF, she is responsible for Physical Claim Substantiation & Sensory testing for Hair & Skin Care. Prior to joining BASF, she spent 5 years at TRI/Princeton as a Senior Research Associate, supporting claim substantiation and fundamental research activities for textile and hair surfaces. She earned a Bachelor of Technology in Chemical Engineering from India and received Master of Science in Chemical Engineering at North Carolina Agriculture & Technical State University focusing on purification of drinking water.

Advances in Antioxidant Technology for Skin Care

by james.runkle@drummondst.com james.runkle@drummondst.com No Comments

In the last two decades the role of antioxidants in skin care has radically changed. In the early 2000s, it was typical to find finished formulas on the shelf that contained butylated hydroxytoluene (BHT) or butylated hydroxyanisole (BHA), which were mostly added to enhance the shelf-life of the product. As time went on, formulas containing vitamin C and vitamin E (alpha-tocopherol) became more common since many studies carried out during that period demonstrated the invaluable benefits provided to the skin by these antioxidants.

As the personal care industry entered the end of the first decade in the new millennium, naturally derived ingredients started to become more and more common. Of course, most of these ingredients were based on botanical ingredients, which are chock-full of polyphenols and other ingredients with antioxidant properties. Antioxidants have also become key components of sunscreen formulas, as research demonstrated unique benefits from the addition of antioxidants in addition to any UV absorption properties. Further, a great deal of research has gone into delivery systems for antioxidants, which provide targeted delivery and stability for antioxidants. Nowadays, one can find antioxidants in just about every type of skin care product in the marketplace. In this article, we will review some of the latest advances in antioxidant technology in the skin care arena.

 

Skin Protection by Antioxidants from Natural Sources

Topical and oral administration of antioxidants for the skin is still a very active field of research [1]. In the personal care industry and academia, a great deal of understanding has been accomplished in the area of topical antioxidant treatments. There are a host of different molecules that have proven to be efficacious for the protection of skin. Some of the most commonly studied antioxidants for topical skin treatment consist of ascorbic acid (vitamin C), alpha-tocopherol (vitamin E), and catechins from green tea. Some other popular ingredients include lycopene, carotene, genistein, rutin, and caffeine [2].

In recent years, most of the focus on new antioxidant product development has been in the botanical arena [1, 3, 4]. Phytochemicals are molecules that are produced by plants. Much effort has gone into understanding their antioxidant, anti-inflammatory, and anti-carcinogenic potential for skin care. There are several recent examples in the literature where the biological activity (antioxidant properties) of botanical ingredients applied to the skin or in cell culture is demonstrated (see Table 1).

Table 1. Examples of studies utilizing botanical ingredients for the treatment of skin.

Source Key Components Efficacy Measurements Reference
Moringa oleifera seed oil Alpha-tocopherol; plant sterols; fatty acids DPPH free radical scavenging assay; skin hydration, erythema melanin values, and elasticity [5]
Brown algae Laminarin (polysaccharide) Collagen fiber density, superoxide production, and expression of antioxidant enzymes in UVB-exposed murine skin [6]
Hibiscus syriacus L. (Malvaceae) Anthocyanin-enriched polyphenols UVB-induced apoptosis, endoplasmic reticulum stress, and mitochondrial reactive oxygen species in HaCaT keratinocytes [7]
Fermented Yak-Kong (a small black soybean) Phenolic acids, isoflavones, and proanthocyanidins Effect of UV exposure on: in vivo wrinkle formation; MMP-1, AP-1, ERK1/2, and JNK1/2 activity in HaCaT keratinocytes; and degradation of collagen in a 3D skin model [8]
       

In some cases, natural ingredients have a limited shelf life or are not stable in different formulation chassis. As such, synthetic ingredients are often inspired by nature. A recent example in the personal care industry is acetyl zingerone, which is structurally similar to zingerone found in the root of the ginger plant, Zingiber officinale [9]. Aguirre-Cruz et al. recently demonstrated the antioxidant potential of peptides, specifically hydrolyzed collagen, to protect the skin from environmental stress [10]. The precise mechanism in which peptides act as antioxidants is not known; however, proton (or electron) donation is suspected to play a role.

In the last decade a tremendous amount of research has been conducted to determine the benefits of molecules from cannabis—a genus of plants from the cannabaceae family. There are a number of phytocannabinoids that have been identified from the hemp plant; however, cannabidiol (CBD) is one of the most studied molecules. Baswan et al. provide a comprehensive review of work conducted in relation to the topical treatment of skin with CDB [11]. It was proposed that CDB has potential to treat eczema, psoriasis, pruritis, and inflammatory conditions.

In addition to topical application, antioxidants and other essential nutrients obtained through the diet (oral consumption) play an integral role in the health state of the skin. This is especially true in regard to moisturization, care of aging skin, and protection against the effects of UV radiation. Many of these key dietary components consist of: omega-3 and omega-6 fatty acids; vitamins A, C, and E; carotenoids; polyphenols; and selenium, zinc, and copper [12].

 

Antioxidant Delivery Systems

Some of the challenges with the conventional delivery of antioxidants stems from their poor solubility, limited shelf-life stability, compromised photostability, and low degree of skin permeability. Delivery systems enhance the ability of antioxidants to carry out their biological function. Various types of emulsion, vesicular, lipid particle, nanoparticle, and nanocarrier systems have been studied and developed in recent years to aid in the stabilization and delivery of antioxidants to the skin.

Emulsions are dispersions of oil and water and can refer to microemulsions, nanoemulsions, and Pickering emulsions. Vesicular systems consist of liposomes, phytosomes, transferomes, ethosomes, and niosomes. Liposomes are the most popular vesicular system used in personal care applications and are composed of concentric layers of phospholipid bilayers spherically shaped with a hollow center for the active ingredient. Barba and coworkers developed nanoliposomes containing vitamin D3, vitamin K2, vitamin E, and curcumin for topical delivery [13]. On their own, these ingredients are unstable and do not penetrate into the skin very well.

Lipid particle systems consist of lipid microparticles and lipid nanoparticles. A recent study showed the utility of caffeic acid lipid nanoparticulate systems for applications in skin [14]. Nanoparticles and nanocarriers continue to be at the forefront of skin care research for their potential at stabilizing and delivering antioxidants to the skin. For example, gold nanoparticles are known for their anti-inflammatory, antiaging, and wound healing properties in skin care [15, 16]. Nanoencapsulation is another area that shows promise for the delivery of lipid soluble antioxidants to the skin [17].

 

Sunscreen Technologies Based on Antioxidants

Exposure of skin to UV radiation can cause direct damage to cellular DNA by crosslinking (UVB) or indirect DNA damage caused by photosensitization reactions (UVA). Photosensitization can occur due to the presence of endogenous (e.g., chromophores in proteins) or exogenous (e.g., UVA sunscreens) species in/on the skin. Almost twenty years ago, Hanson and Clegg demonstrated that sunscreen photoprotection could be enhanced if antioxidants were included in the formula [18]. This has become such an important area of research that the Journal of Photochemistry and Photobiology has recently announced that it will dedicate a special issue to the topic of endogenous photosensitizers and their roles in skin photodamage and photoprotection.

The majority of commercial sunscreen formulas contain antioxidants [1]. In part, this is due to the popularity of including botanical ingredients in skin care products. However, the presence of antioxidant species can ameliorate damage caused during and after sun exposure by reactive oxygen species. A recent review by Giacomoni presents this case in relation to the activity of molecules capable of impeding the damaging effects of superoxide anion and singlet oxygen [19].

Concluding Remarks

In the last several years, there has been significant progress in the scientific understanding of antioxidant treatment of the skin. Everly increasing numbers of studies of new ingredients continue to appear in the literature. Hopefully, in the years to come there will be some type of method harmonization across institutes and industry to more uniformly characterize antioxidant behavior from the vast array of botanical ingredients. Many antioxidants are unstable or not easily bioavailable after treatment. To circumvent these challenges, antioxidant delivery systems have been developed and show much promise in the future. Finally, antioxidants play an integral role in sun protection. They are incorporated into sunscreen formulas for their ability to ameliorate damage induced by reactive oxygen species resulting from exposure to UV radiation.

 

References

  1. McMullen, R., Antioxidants and the Skin. 2nd ed. 2019, Boca Raton, FL: CRC Press.
  2. Azevedo Martins, T.E., C.A. Sales de Oliveira Pinto, A. Costa de Oliveira, M.V. Robles Velasco, A.R. Gorriti Guitiérrez, M.F. Cosquillo Rafael, J.P.H. Tarazona, and M.G. Retuerto-Figueroa, Contribution of topical antioxidants to maintain healthy skin—A review. Scientia Pharmaceutica, 2020. 88(2): p. 27.
  3. Herranz-López, M. and E. Barrajón-Catalán, Antioxidants and skin protection. Antioxidants, 2020. 9: p. 704.
  4. Petruk, G., R. Del Giudice, M.M. Rigano, and D.M. Monti, Antioxidants from plants protect against skin photoaging. Oxid. Med. Cell. Longev., 2018. 2018: p. 1454936.
  5. Athikomkulchai, S., P. Tunit, S. Tadtong, P. Jantrawut, S. Sommano, and C. Chittasupho, Moringa oleifera seed oil formulation physical stability and chemical constituents for enhancing skin hydration and antioxidant activity. Antioxidants, 2021. 8(1): p. 2.
  6. Ahn, J., D. Kim, C. Park, B. Kim, H. Sim, H. Kim, T.-K. Lee, J.-C. Lee, G. Yang, Y. Her, J. Park, T. Sim, H. Lee, and M.-H. Won, Laminarin attenuates ultraviolet-induced skin damage by reducing superoxide anion levels and increasing endogenous antioxidants in the dorsal skin of mice. Mar. Drugs, 2020. 18: p. 345.
  7. Karunarathne, W., I. Molagoda, K. Lee, Y. Choi, S.-M. Yu, C.-H. Kang, and G.-Y. Kim, Protective effect of anthocyanin-enriched polyphenols from Hibiscus syriacus L. (Malvaceae) against ultraviolet B-induced damage. Antioxidants, 2021. 10: p. 584.
  8. H, P., S. JW, L. TK, K. JH, K. JE, L. TG, P. JHY, H. CS, Y. H, and L. KW, Ethanol extract of yak-kong fermented by lactic acid bacteria from a Korean infant markedly reduces matrix metallopreteinase-1 expression induced by solar ultraviolet irradiation in human keratinocytes and a 3D skin model. Antioxidants, 2021. 10(2): p. 291.
  9. Chaudhuri, R., T. Meyer, S. Premi, and D. Brash, Omni antioxidant: Acetyl zingerone scavenges/quenches reactive species, selectively chelates iron. Int. J. Cosmet. Sci., 2020. 42: p. 36-45.
  10. Aguirre-Cruz, G., A. León-López, V. Cruz-Gómez, R. Jiménez-Alvarado, and G. Aguirre-Álvarez, Collagen hydrolysates for skin protection: Oral administration and topical formulation. Antioxidants, 2020. 9(2): p. 181.
  11. Baswan, S., A. Klosner, K. Glynn, A. Rajgopal, K. Malik, S. Yim, and N. Stern, Therapeutic potential of cannabidiol (CBD) for skin health and disorders. Clin. Cosmet. Investig. Dermatol., 2020. 13: p. 927-942.
  12. Michalak, M., M. Pierzak, B. Kręcisz, and E. Suliga, Bioactive compounds for skin health: A review. Nutrients, 2021. 13: p. 203.
  13. Bochicchio, S., A. Dalmoro, V. De Simone, P. Bertoncin, G. Lamberti, and A.A. Barba, Simil-microfluidic nanotechnology in manufacturing of liposomes as hydrophobic antioxidants skin release systems. Cosmetics, 2020. 7(2): p. 22.
  14. Hallan, S., M. Sguizzato, M. Drechsler, P. Mariani, L. Montesi, R. Cortesi, S. Björklund, T. Ruzgas, and E. Esposito, The potential of caffeic acid lipid nanoparticulate systems for skin application: In vitro assays to assess delivery and antioxidant effect. Nanomaterials, 2021. 11(1): p. 171.
  15. Ben Haddada, M., E. Gerometta, R. Chawech, J. Sorres, A. Bialecki, S. Pesnel, J. Spadavecchia, and A.-L. Morel, Assessment of antioxidant and dermoprotective activities of gold nanoparticles as safe cosmetic ingredient. Colloid. Surface. B, 2020. 189: p. 110855.
  16. Gubitosa, J., V. Rizzi, P. Fini, R. Del Sole, A. Lopedota, V. Laquintana, N. Denora, A. Agostiano, and P. Cosma, Multifunctional green synthetized gold nanoparticles/chitosan/ellagic acid self-assembly: Antioxidant, sun filter and tyrosinase-inhibitor properties. Mater. Sci. Eng. C, 2020. 106: p. 110170.
  17. Davies, S., R.V. Contri, S.S. Guterres, A.R. Pohlmann, and I.C.K. Guerreiro, Simultaneous nanoencapsulation of lipoic acid and resveratrol with improved antioxidant properties for the skin. Colloid. Surface. B, 2020. 192: p. 111023.
  18. Hanson, K. and R. Clegg, Bioconvertible vitamin antioxidants improve sunscreen photoprotection against UV-induced reactive oxygen species. J. Cosmet. Sci., 2003. 54(6): p. 589-598.
  19. Giacomoni, P., Appropriate technologies to accompany sunscreens in the battle against ultraviolet, superoxide, and singlet oxygen. Antioxidants, 2020. 9: p. 1091.

Roger L. McMullen, Ph.D.

Dr. Roger McMullen has over 20 years of experience in the personal care industry with specialties in optics, imaging, and spectroscopy of hair and skin. Currently, he is a Principal Scientist at Ashland Specialty Ingredients G.P. and leads the Material Science team in the Measurement Science department. Roger has over 30 publications in peer-reviewed journals and textbooks. He is also the author of Antioxidants and the Skin, 2nd edition and founded the online news magazine The Cosmetic Chemist. Roger received a B.S. in Chemistry from Saint Vincent College and completed his Ph.D. in Biophysical Chemistry at Seton Hall University.

Roger actively engages and participates in educational activities in the personal care industry. He frequently teaches continuing education courses for the SCC and TRI-Princeton. In addition, Roger is an Adjunct Professor at Fairleigh Dickinson University and teaches Biochemistry to students pursuing M.S. degrees in Cosmetic Science and Pharmaceutical Chemistry. Prior to pursuing a career in science, Roger served in the U.S. Navy for four years on board the USS YORKTOWN (CG 48). He is fluent in Spanish and Catalan and currently is learning to play the classical guitar.

Exposome and Skin Care

by james.runkle@drummondst.com james.runkle@drummondst.com No Comments

What is the Exposome?  According to the CDC/NIOSH[1] website, the exposome can be defined as: “the measure of all the exposures of an individual in a lifetime and how those exposures relate to health.  An individual’s exposure begins before birth and includes insults from environmental and occupational sources.  Understanding how exposures from our environment, diet, lifestyle, etc. interact with our own unique characteristics such as genetics, physiology, and epigenetics impact our health is how the exposome will be articulated.” [2]  In other words, the exposome is the analysis of risk factors encompassing environmental exposures (chemicals, diet, stress, and physical factors), behaviors and genetic variations with overall corresponding biological responses.  This relatively new concept and approach in epidemiological and biomedical research has stirred up some excitement among scientists, with many calling for more efforts to map the human exposome,[3] in order to safeguard future generations from the increasing number of chemical pollutants in our environment.  In this blog, we discuss the main factors comprising the skin aging exposome and how they impact our personal care and skin health.

The Skin Aging Exposome

Skin aging is caused by a combination of two cumulative processes: (1) intrinsic aging and (2) extrinsic aging.  The former is the normal genetic process that occurs over time, including body’s internal oxidation due to metabolic activities and oxygen consumption;[4] while the latter, or accelerated aging, is resulted from exposure to skin exposome factors (Figure 1).  Extrinsic environmental factors, such as sunlight, pollution, and climate, can trigger biological processes that participate and accelerate skin aging.  Self-induced factors, such as smoking, and lifestyle choices also play a role in potentiating skin aging.

Specifically, Krutmann et al.[5] have proposed the following environmental factors as part of the skin aging exposome: (1) solar radiation: ultraviolet radiation, visible light and infrared radiation, (2) air pollution (ozone and diesel exhaust), (3) tobacco smoke, (4) nutrition, (5) other miscellaneous factors, including lifestyle choices and use of cosmetic products.  In fact, it is estimated as high as 80% of skin aging signs are caused by the exposome.[6], [7]  It is important to note that skin exposome factors often act synergistically to accelerate the aging process.  For instance, “photo-pollution”[8] is the exposome resulted from the synergistic combination of sunlight and pollution.  In the following, we will briefly describe each skin aging exposome factor.

  1. Solar Radiation

Since ancient times, humans have tried various methods to shield the harmful solar radiation and protect skin against the adverse effects of the sun.  In modern times, more sophisticated photoprotection products, i.e., sunscreen and/or daily skin care products, have been developed for the prevention of acute (e.g., sunburn) and chronic (e.g., skin cancer and photoaging) skin damage that may result from exposure to ultraviolet rays (UVB and UVA).

However, with recent advances in skin care research, we have learned that wavelengths beyond the ultraviolet spectrum (UVB, 290–320 nm, and UVA, 320–400 nm), visible light (400–770 nm) and infrared (IR) radiation (770 nm–1 mm), contribute to skin damage in general and photoaging including pigmentary problems of human skin (Figure 2).[9]  Consequently, attempts have been made to develop sunscreen and skin care products that not only protect against UVB or UVA radiation but also provide photoprotection against visible light and infrared radiations.[10]

1.1 Ultraviolet (UV) Radiation

The role of UV radiation in skin aging is well established and the term “photoaging” is coined to emphasize this cause-and-effect relationship.  This is the most studied exposome factor in skin aging for the past several decades.  Herein we will summarize a few key points from review articles on the role of UV radiations in skin aging:[11],[12],[13],[14]

    • Exposure to UV radiation is the primary factor of extrinsic skin aging. It affects all three layers of the skin, e., the epidermis, dermis and hypodermis.  This is the primary cause of early, premature wrinkles, sagging skin and pigmentation.
    • All UV wavelengths (UVB, UVA2 and UVA1) rays contribute to photoaging of human skin.
    • Susceptibility is strongly influenced by endogenous protection systems in human skin, such as skin pigmentation, DNA repair, antioxidant defense, etc.
    • Acute stress responses and chronic damage responses drive the skin aging process.
    • Photoaging mainly results from daily exposure to non-extreme, low doses radiation. UVA rays, in particularly long wavelength UVA1 is a major contributor.
    • Lastly and most importantly, it is highly probable that the regular use of sunscreens can help delay the photoaging process of human skin.

1.2 Visible Light (VL)

Of even lesser energy, visible light (400–700 nm) accounts for approximately 50% of the total solar spectrum.  It penetrates deeply into biological tissues and about 20% reaches the hypodermis.  Evidence suggests that VL plays a fundamental role in hyperpigmentation, particularly in individuals with deeper skin phototypes (Fitzpatrick skin type III-VI) where persistent pigment darkening has been observed following VL exposure.[15], [16]  It is demonstrated that the lower wavelength, higher energy portion of visible light (blue-violet light from 400 to 500 nm) is responsible for the highest pigmentation induced by VL.  Even the green part of VL accounts for more than 30% of skin pigmentation.[17]  Studies have shown that physiological doses comparable to 90 – 150 min of midday summer sun exposure can induce lasting pigmentation.16 Recently, a unique mechanism involving activation of melanogenesis via the opsin 3 photoreceptor has been described.[18]

1.3 Infrared (IR) Radiation

IR rays accounts for approximately 45% of the total solar energy received.  Only the shortest wavelengths, IR-A (770-1400 nm) have sufficient energy for skin penetration to cause significant damage.  IR radiation is known to upregulate the production of matrix metalloproteinases (MMPs), enzymes that facilitate the degradation of extracellular matrix proteins.[19]  The earliest biological event that occurs after IR-A radiation in human fibroblasts is an increase in the intra-mitochondrial production of reactive oxygen species (ROS).  There is a shift in the glutathione equilibrium to its oxidized state.  The discovery of this mitochondrial signaling response caused by IR-A has a direct clinical impact as it indicates that the use of antioxidants may be an effective strategy to help protect the skin against effects from IR-A.

  1. Air Pollution and Tobacco Smoking

Exposures to pollutants, exhaust, smog-derived ozone and cigarette smoke have been associated with accelerated skin ageing (pigmentation, loss of elasticity and wrinkles) and increased cancer risks.[20]  Airborne particles (particulate matters, PM), rich in polycyclic aromatic hydrocarbons (PAHs), can exert detrimental effects on human skin and contribute to facial lentigines formation.[21]  In general, topical exposure to pollutants harms the skin by increasing oxidative stress that modifies lipid DNA and protein function.[22], [23], [24]  Soeur and coworkers at L’Oréal demonstrated the effect of “photo-pollution”, where with exposure to UVA1 irradiation (i.e., long UVA, 350-400 nm), which accounts for 80% of daily UV and can easily reach dermal-epidermal junction in skin, air pollutants (in particular, PAHs) were phototoxic even at very low concentrations (nanomolar range) on cultured cells or in reconstructed epidermis.  Thus, the impact of PAHs reacting to long UVA synergistically increases the oxidative stress, which may impair cutaneous homeostasis and aggravate sunlight-induced skin damage.

Exposure to pollution also decreases skin quality and exacerbates existing skin conditions, such as atopic dermatitis (AD) and acne.[25]  Various scientific studies show an undeniable link between air pollution (including cigarette smoke) and pigmentation, loss of elasticity and wrinkles.  These factors share a common mechanism involving the aryl hydrocarbon receptor (AhR).[26]  Based on available studies, many of the adverse effects caused by air pollution may be mediated via AhR signaling in human skin.  In addition to topical exposure, humans are exposed to PAHs via systemic accumulation in the body.  This is evident by measuring the pollutants in the hair fibers.[27]  Naudin et al. have confirmed that speed of naturally occurring hair-cortex degradation and cuticle delamination is increased in fibers with increased PAH concentrations.  Further, hair fiber with exposure to UV irradiation leads to more pronounced cuticle damage, especially around samples with higher PAH concentrations.  This detrimental effect of PAHs together with UV irradiation, i.e., photo-pollution, is likely to be seen with other human tissues.

  1. Diet / Nutrient

Dietary factors and nutritional supplements may influence skin health.  Eating unhealthy food has been associated with numerous skin problems, ranging from acne to signs of skin aging.  On the other hand, a healthy diet rich in antioxidants may delay chronological aging effects.  In a study of facial aging in twins, twins who avoid excessive alcohol intake have a younger perceived age.[28]  Consuming too much sugar is suggested to contribute to wrinkles, due to a natural process, known as glycation,[29] where sugar in the blood stream binds to proteins to form harmful molecules called “advanced glycation end products” (AGEs), aka. the Maillard reaction.  Another risk factor associated with food consumption is unintentional ingestion of PAHs.  In addition to inhalation and skin contact of PAHs as a result of air pollution, people can be exposed to PAHs by consuming charbroiled foods (smoke meat, or grilled over charcoal, diesel exhausts, etc.).[30]  Such consumption may contribute to skin damages following systemic exposures.

  1. Stress and Sleep Deprivation

It is known that stress creates elevated levels of cortisol hormones which cause inflammation in the body.  Inflammation leads to increased collagen breakdown and exacerbation of skin conditions such as acne, rosacea, eczema and wound healing.  Though it may seem intuitive to link physiological stress and skin aging, the underlying mechanisms are not well defined.  However, one plausible mechanism was demonstrated by studies of the correlation between psychological stress and permeability barrier homeostasis in human cutaneous functions, thus explaining how psychological stress can lead to a decline in epidermal permeability and deterioration in barrier disruption and recovery, followed by the induction, exacerbation, and propagation of inflammatory skin disorders. [31], [32]

Further to acute psychosocial stress, sleep deprivation is associated with increased signs of intrinsic skin aging (fine lines, uneven pigmentation, reduced elasticity), most likely due to its disruption of skin barrier function homeostasis, and that this disruption may lead to much slower recovery rates after skin barrier disruption and lower satisfaction with appearance.[33]

Exposome and Acne

Acne is caused by inflammation of the pilosebaceous follicle, occurring commonly in adolescents and some adults.  Clinically, inflammatory acne causes skin damages and formation of skin lesions, including micro-comedones, papules, and pustules.  In some people, scarring from acne can be persistent.[34]

Several exposome factors, including diet, pollution, medication, microbiota, and cosmetics, have been implicated in development and exacerbation of acne (Figure 3).23 This argument is confirmed in a recent international survey with 11,000 participants, aged between 15 and 39 years, with clinically confirmed acne or without acne.  Consumption of dairy products, sweets, alcohol or whey proteins, as well as exposure to pollution, stress, certain mechanical factors and humid or hot weather or sun exposure, were significantly (all P ≤ 0.05) more frequently reported for the acne group than for the control group.[35]  Some topical skincare and makeup products containing essential oils, powders, and alkaline skin cleansers and soaps have been associated with acne.23  Use of mild cleansers on a regular basis to keep the skin surface free of oil, dirt and debris can help prevent acne.

Maskne

For decades in some Asian countries, people regularly wear face masks to reduce the inhalation of pollution-related particles.  It has nowadays taken another facet, i.e., to limit the spread of harmful viruses such as COVID-19.  However, the negative impact of repetitive and prolonged mask wearing may cause “maskne” or mask-related acne and other skin issues, including breakouts, clogged pores, redness, itchiness and imperfections.  Maskne is essentially a subset of acne mechanica, due to friction/rubbing from the mask, causing local pressure on the sweat glands and irritation of the skin barrier.[36], [37]  Further exacerbation is induced by increased temperature and trapped moisture in the mask area due to the continuous use of face masks.  No studies to date have evaluated “maskne”, however, current data suggests maskne is likely a result of local temperature changes and skin microflora dysbiosis.[38]  General advise for dealing with maskne includes: (1) avoid wearing makeup under the mask area, (2) use mild facial cleanser containing salicylic acid, (3) topical moisturizer to hydrate and maintain skin barrier functions, and (4) change masks regularly.

Taking on the Exposome

In a 2016 review article, Dr. Sainani summarized progress in exposome research, including Environment-Wide Association Studies and novel data collection techniques, as well as significant remaining challenges in collecting, analyzing, and interpreting exposome data.  The article concludes with a call to adopt a “big science” approach akin to the Human Genome Project, with investments in improving measurement techniques, establishing public databases with agreed upon standards, and strong community leadership.[39]

In a recent JEADV paper, Appenzeller et al. studied hair samples from 204 women from two Chinese cities with different levels of pollution.  The hair analysis, together with “omics” data (metabolomics, proteomics, genomics and microbiome), provided access to information for assessing chronic exposure to pollution (particularly, PAHs) and shed light on the molecular mechanisms of the combined effects of exposome factors, including solar radiation and other environmental exposure.[40]

Further to the study on hair samples, De Vecchi et al. have evaluated the impact of several environmental aggressors on human surfaces, using portable and wearable devices for monitoring exposome.[41]  The work was carried out by two bicyclists wearing multiple sensors to capture the meteorological conditions by biking through urban areas in summer and in winter in Brazil.  Correlated with GPS and monitoring data, all these results provide insights on how environmental stressors affect the quality of different hair types and body surface according to exposure routine.  Additional study was designed to quantify environmental exposures during routine daily activities to provide quantitative metrics that inspire future studies on exposome and human health.[42]

Summary and Conclusions

Based on several reviewed articles, it is undeniable that most skin aging processes are affected by numerous different exposome factors.  In order to mitigate the negative impacts of such factors, further development of the nascent holistic approach will be important for the cosmetic field.  In particular, a comprehensive approach is essential to understanding how the sum of all factors are affecting skin health and skin aging on the individual level and how to further define the appropriate recommendations, such as lifestyle changes, nutritional adjustments, adequate cosmetic formulations, and personalized beauty routine, to alleviate the negative impacts of such factors.  While exposome factors cannot be completely avoided, a conscious awareness, limited exposure and healthy lifestyle can help reduce their negative effects on skin health.

Acknowledgement

The authors are most grateful to Luc Aguilar for his review and suggestions for the manuscript.  In addition, we would like to thank the kind review and comments from Giorgio Dell’Acqua, Ronni Weinkauf, Jean-Baptiste Galey, Gustavo Luengo, and the L’Oréal Reading Committee.

 

Figure 1.  The skin aging exposome.  These factors have been identified to have detrimental effects on skin health.  Exposure to sunlight, pollution and tobacco smoking are shown to trigger molecular processes that damage the skin structure, leading to premature skin aging.  Other factors, recently recognized and thus less studied, have also shown to be potentiators for skin aging.  These factors can act independently or interact synergistically with each other to accelerate the skin aging process.  [J. Krutmann, et al., The Skin Aging Exposome, J Dermatol Sci (2017)].

 

Figure 2.  The solar spectrum with various wavelengths, which penetrate skin at different levels.  The longer the wavelengths the deeper the rays penetrate the skin.  Each wavelength has both different and overlapping effects.  UV = Ultraviolet radiation, ROS = Reactive Oxygen Species, RNS = Reactive Nitrogen Species.  [Modified from J. Krutmann, et al., The Skin Aging Exposome, J Dermatol Sci (2017) with updated data from H. Lim publications].

Figure 3.  The exposome factors impacting acne.  [B. Dreno, et al., J Eur Acad Dermatol Venereol, (2018)]

 

References:

[1] CDC = Centers for Disease Control and Prevention, NIOSH = National Institute for Occupational Safety and Health.

[2]https://www.cdc.gov/niosh/topics/exposome/default.html#:~:text=The%20exposome%20can%20be%20defined,from%20environmental%20and%20occupational%20sources (Accessed on April 1, 2021)

[3]  http://alliance.nautil.us/article/242/mapping-the-human-exposome (Accessed on April 4, 2021)

[4]  Van Beek, J.H.G.M., Kirkwood, T.B.L., Bassingthwaighte, J.B. ‘Understanding the physiology of the ageing individual: computational modelling of changes in metabolism and endurance’, Interface Focus.06 April 2016.  http://doi.org/10.1098/rsfs.2015.0079

[5]  Krutmann, J., Bouloc, A., Sore, G., Bernard, B.A., Passeron, T. ‘The skin aging exposome’, J Dermatol Sci. 2017 Mar; 85(3):152-161. doi: 10.1016/j.jdermsci.2016.09.015.

[6]  https://www.vichyusa.com/vichy-exposome (Accessed on April 6, 2021)

[7]  Friedman, O., ‘Changes associated with the aging face’, Facial Plast Surg Clin North Am. 2005 Aug; 13(3):371-80.

[8]  Soeur, J., Belaïdi, J.P., Chollet, C., Denat, L., Dimitrov, A., Jones, C., Perez, P., Zanini, M., Zobiri, O., Mezzache, S., Erdmann, D., Lereaux, G., Eilstein, J., Marrot, L. ‘Photo-pollution stress in skin: Traces of pollutants (PAH and particulate matter) impair redox homeostasis in keratinocytes exposed to UVA1’. J Dermatol Sci. 2017 May;86(2):162-169. doi: 10.1016/j.jdermsci.2017.01.007. Epub 2017 Jan 16. PMID: 28153538.

[9]  Note that IR rays do not trigger pigmentation.  See Geisler, A.N., Austin, E., Nguyen, J., Hamzavi, I., Jagdeo, J., Lim, H.W. ‘Visible light. Part II: Photoprotection against visible and ultraviolet light’, J American Academy of Dermatol, Volume 84, issue 5 (May 2021).

[10]  Dupont, E., Gomez, J., Bilodeau, D. ‘Beyond UV radiation: a skin under challenge’, Int J Cosmet Sci. 2013 Jun;35(3):224-32. doi: 10.1111/ics.12036. Epub 2013 Feb 14. PMID: 23406155.

[11] Marionnet, C., Tricaud, C., Bernerd, F. ‘Exposure to non-extreme solar UV daylight: spectral characterization, effects on skin and photoprotection’, Int J Mol Sci, 2014, 16: 68-90

[12] Battie, C., Jitsukawa, S., Bernerd, F., Del Bino, S., Marionnet, C., Verschoore, M. ‘New insights in photoaging, UVA induced damage and skin types’, Exp Dermatol, 2014, 23 Suppl 1: 7-12.

[13] Kligman, L. H., Kligman, A.M., ‘The nature of photoaging: its prevention and repair’, Photodermatol, 1986, 3: 215-27.

[14] Flament, F., Bazin, R., Laquieze, S., Rubert, V., Simonpietri, E., Piot, B., ‘Effect of the sun on visible clinical signs of aging in Caucasian skin’, Clin Cosmet Investig Dermatol, 2013, 6: 221-32

[15]  Mahmoud, B.H., Ruvolo, E., Hexsel, C.L., Liu, Y., Owen, M.R., Kollias, N., Lim, H.W., Hamzavi, I.H. ‘Impact of Long-Wavelength UVA and Visible Light on Melanocompetent Skin’, J Invest Dermatol. 2010, 130: 2092-97.

[16]  Duteil, L., Cardot-Leccia, N., Queille-Roussel, C., Maubert, Y., Harmelin, Y., Boukari, F., Ambrosetti, D., Lacour, J.P., Passeron, T. ‘Differences in visible light-induced pigmentation according to wavelengths: a clinical and histological study in comparison with UVB exposure’, Pigment Cell Melanoma Res2014, Sep.; 27(5):822-6.

[17] Personal communication with L. Aguilar.

[18] Regazzetti, C., Sormani, L., Debayle, D., Bernerd, F., Tulic, M.K., De Donatis, G.M., et al. ‘Melanocytes sense blue light and regulate pigmentation through the Opsin-3’, J Invest Dermatol. 2018, 138:171–8

[19] Vierkotter, A., Krutmann, J. ‘Environmental influences on skin aging and ethnic-specific manifestations’, Dermatoendocrinol, 2012 4: 227-31.

[20] Drakaki, E., Dessinioti, C., Antoniou, C.V. ‘Air pollution and the skin’, Front. Environ. Sci., 15 May 2014, doi.org/10.3389/fenvs.2014.00011

[21] Vierkötter, A., Schikowski, T., Ranft, U., Sugiri D., Matsui, M., Krämer U., Krutmann J.  ‘Airborne particle exposure and extrinsic skin aging’, J Invest Dermatol. 2010 Dec;130(12):2719-26.

[22] Marrot, L. ‘Pollution and Sun Exposure: A Deleterious Synergy. Mechanisms and Opportunities for Skin Protection’, Curr Med Chem, 2018, 25: 5469-86.

[23] Dreno, B., Bettoli, V., Araviiskaia, E., Sanchez Viera, M., Bouloc, A. ‘The influence of exposome on acne’, J Eur Acad Dermatol Venereol, 2018, 32: 812-19.

[24] Lefebvre, M. A., Pham, D.M., Boussouira, B., Bernard, D., Camus, C., Nguyen, Q.L. ‘Evaluation of the impact of urban pollution on the quality of skin: a multicentre study in Mexico’, Int J Cosmet Sci, 2015, 37: 329-38.

[25] Lefebvre, M. A., Pham, D.M., Boussouira, B., Qiu, H., Ye, C., Long, X., Chen, R., Gu, W., Laurent, A., Nguyen, Q.L., ‘Consequences of urban pollution upon skin status. A controlled study in Shanghai area’, Int J Cosmet Sci, 2016, 38: 217-23.

[26] Abel, J., Haarmann-Stemmann, T. An introduction to the molecular basics of aryl hydrocarbon receptor biology. Biol. Chem. 2010, 391, 1235-1248.

[27] Naudin, G., Bastien, P., Mezzache, S., Trehu, E., Bourokba, N., Appenzeller, B.M.R., Soeur, J., Bornschlögl, T. ‘Human pollution exposure correlates with accelerated ultrastructural degradation of hair fibers’, Proceedings of the National Academy of Sciences Sep 2019, 116 (37) 18410-18415; DOI: 10.1073/pnas.1904082116

[28] Rowe, D.J., Guyuron, B., ‘Environmental and genetic factors in facial aging in twins’, in: Textbook of Aging Skin (Farage, M. A., Miller, K. W. and Maibach, H. I., eds.) pp. 441–446. Springer Berlin, Heidelberg (2010).

[29] Draelos, Z.D., Pugliese, P.T. ‘Glycation and skin aging: a review’, Cosmet. Toiletries Sci. Appl. 2011, 126 (6) 438.

[30] Hokkanen, M., Luhtasela, U., Kostamo, P., Ritvanen, T., Peltonen, K., & Jestoi, M. ‘Critical Effects of Smoking Parameters on the Levels of Polycyclic Aromatic Hydrocarbons in Traditionally Smoked Fish and Meat Products in Finland’. Journal of Chemistry2018. https://doi.org/10.1155/2018/2160958

[31] Garg, A., Chren, M.M., Sands, L.P., Matsui, M.S., Marenus, K.D., Feingold, K.R., Elias, P.M. ‘Psychological stress perturbs epidermal permeability barrier homeostasis: implications for the pathogenesis of stress- associated skin disorders’. Arch Dermatol. 2001 Jan;137(1):53-9.

[32] Altemus, M., Rao, B., Dhabhar, F.S., Ding, W., Granstein, R.D.  ‘Stress-induced changes in skin barrier function in healthy women’. J Invest Dermatol. 2001 Aug;117(2):309-17.

[33] Walia, H.K., Mehra, R. ‘Overview of Common Sleep Disorders and Intersection with Dermatologic Conditions’, Int J Mol Sci. 2016 Apr 30;17(5):654. doi: 10.3390/ijms17050654.

[34] Ramasamy, S., Barnard, E., Dawson, Jr., T.L., Li, H., ‘The role of the skin microbiota in acne pathophysiology’, Br J Dermatol, 2019, 181: 691-9.

[35] Dreno, B., Shourick, J., Kerob, D., Bouloc, A., Taïeb, C. ‘The role of exposome in acne: results from an international patient survey’, J Eur Acad Dermatol Venereol. 2020 May; 34(5):1057-1064.

[36] Sinha, A. & Singh, A. R. ‘An Unforeseen Hazard of Masks Being in Vogue’. Int. J. Occup. Environ. Med. 2020, 11, 213–214.

[37] Teo, W. ‘The “Maskne” microbiome – pathophysiology and therapeutics’. Int. J. Dermatol. 2021, doi:10.1111/ijd.15425.

[38] Searle, T., Ali, F. R., Al-Niaimi, F. ‘Identifying and addressing “Maskne” in clinical practice’. Dermatol. Ther. 2020, 8–9. doi:10.1111/dth.14589.

[39] Sainani, K.’ Taking on the Exposome: Bringing Bioinformatics Tools to the Environmental Side of the Health Equation’. Biomedical Computation Review November 1st (2016).

[40] Appenzeller, B.M.R., Chadeau-Hyam, M., Aguilar, L. ‘Skin exposome science in practice: current evidence on hair biomonitoring and future perspectives’’, JEADV 2020, 34 (Suppl. 4), 26-30.

[41] De Vecchi, R., da Silveira Carvalho Ripper, J., Roy, D., Breton L., Germano Marciano, A., Bernardo de Souza, P.M., de Paula Corrêa, M. ‘Using wearable devices for assessing the impacts of hair exposome in Brazil’. Sci Rep. 2019 Sep 16;9(1):13357. doi: 10.1038/s41598-019-49902-7. PMID: 31527774; PMCID: PMC6746720.

[42] De Paula Corrêa, M., Germano Marciano, A., Silveira Barreto Carvalho, V., Bernardo de Souza, P.M., da Silveira Carvalho Ripper, J., Breton, L., Roy, D., De Vecchi, R. ‘Exposome extrinsic factors in the tropics: the need for skin protection beyond solar UV radiation’, Science of The Total Environment, 2021, 146921, ISSN 0048-9697.

 

AUTHORS

Catherine CHIOU,a Gabrielle SORE,b Stephen LYNCHa

a L’Oréal Research and Innovation, Clark, NJ, USA

b L’Oréal Research and Innovation, Chevilly Larue, France

 

Catherine Chiou, PhD.

Dr. Catherine Chiou holds a BS degree in Chemistry from National Taiwan University and a Ph.D. in Bioinorganic Chemistry from the University of Minnesota.  Catherine’s NIH Postdoctoral fellowship training in Synthetic Chemistry took place at Harvard University.  Her first industrial position was with Unilever Research US in the laundry bleach research program and machine dishwashing detergent research, including I&I applications.

Catherine began her career in cosmetic field at L’Oréal USA in 2001 in the DIMP (International Raw Materials Department).  She worked on all aspects of “innovative raw material” functions, including scouting new supplier innovations, and managing supplier relationships.  In addition, Catherine served a stint within the PCPC INCI Committee.

Catherine is currently an Associate Principal Scientist at L’Oréal USA in the Cosmetic Application Domain, focusing on developing skin cleansing and makeup removing technologies.  Prior to the current position, she has worked in the skin care research and innovation lab as a senior formulator, contributing towards development of platform technologies and several global launches of skin care treatment products.  She is an inventor for more than 20 US and international patents.  She is a current member of scientific committee of NYSCC.

Gabrielle Sore, PhD.

Dr. Gabrielle Sore is a pharmacist with a Ph.D. in dermal pharmacology. She has been working for more than 30 years in the cosmetic industry. Dr. Sore spent the last 29 years in L’Oréal where she worked in France, in Japan, and in the United States. During Gabrielle’s career, she worked mostly in the scientific communication of skin care, make-up and specific eye products; and she was more specifically in charge of scientific communication of dermatological brands like Vichy, La Roche Posay, SkinCeuticals for which her role is to coordinate the information within the Research, Marketing and Development teams.

Stephen Lynch, PhD.

Dr. Stephen Lynch holds a PhD in organic chemistry and spent 10 years in the pharmaceutical industry conducting drug discovery research.   For the past 7 years he has worked for L’Oréal USA Research & Innovation where he currently serves as Director of Skincare Scientific Affairs.  In this capacity he helps to identify cosmetic ingredients, coordinate innovative testing, and translate scientific concepts in support of skincare product development.

 

 

Hand sanitizers: Regulatory Overview and Formulations

by james.runkle@drummondst.com james.runkle@drummondst.com No Comments

The use of hand sanitizers has steadily increased over the past ten years.  Their use began in hospitals, doctor’s offices, clinics and healthcare facilities.  Then, we started seeing dispensers in building entrances, by elevators and in many common areas.  Due to the recent COVID pandemic, there was an exponential increase in the use of hand sanitizers. Dispensers were placed in most store’s entrances and in multiple locations in every store.  Hand sanitizers were no longer sold in pharmacies only, but they are sold everywhere, including hardware stores.  One can purchase a gallon of sanitizing hand lotion at a time instead of the usual 12 to 16 oz containers.

In the United States, hand sanitizers are also called “consumer antiseptic rubs” and are regulated by the Food and Drug Administration (FDA).  They are considered Over the Counter Drugs (OTC) and fall under the Consumer Antiseptic Rub Products Monograph.  This monograph is not finalized yet, but tentative final monographs have been published in the Federal Register in 2016, 2017 and 20191,2,3.  The most recent tentative final monograph does not classify any active as Category I (Safe and effective).  However, it classifies three actives as Category III (More data needed for safety and efficacy).  These actives are:

  1. Alcohol at 60-90%.
  2. Isopropyl Alcohol at 70-91.3%.
  3. Benzalkonium Chloride.

The monograph requires marketers of such products to test the products for safety and efficacy.  Efficacy should be tested both in vitro and in vivoIn vitro testing requires the determination of antimicrobial activity of the antibacterial active by conducting a battery of antimicrobial tests using certain bacterial strains.  Three tests are suggested in the monograph, namely Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC) and time-kill testing of certain strains.  Regarding in vivo testing, the monograph specifies conducting two clinical studies with a minimum enrollment of 100-person each in two separate centers to evaluate efficacy.   Efficacy is typically evaluated using bacterial log reduction after product application as compared to a placebo.

Due to the recent COVID pandemic, the FDA issued a temporary guidance for alcohol-based hand sanitizer production4.  The guidance allowed FDA-registered manufacturers to produce alcohol-based hand sanitizers based on the following formulation:

  1. Alcohol (ethanol formulated to 80% v/v) in aqueous solution or Isopropyl Alcohol (formulated to 75% v/v) in aqueous solution.
  2. Glycerin 1.45% v/v
  3. Hydrogen Peroxide (0.125% v/v)
  4. Sterile distilled water or boiled cold water.

The stipulation was that other additives cannot be added to this formulation, including fragrance.  The formulation is not supposed to be thickened and should be in the form of a solution only.  The formulation cannot be used as a foam or an aerosol either.

Now let’s talk about the fun stuff, formulating a hand sanitizer product.  The leading method of dispensing hand sanitizers in most facilities are the motion-sensing foam dispensers.  These dispensers typically are filled with an alcohol-based solution that foams when dispensed.  The formulation contains 70% alcohol for sanitizing and PEG-12 dimethicone as a foaming agent.  It also contains glycerin (a well-known moisturizer), tocopherol acetate and a couple of esters to replenish skin lipids as well as a mild fragrance to cover the alcohol smell.

The second most popular form of hand sanitizers on the market is the gel.  Most gels are formulations containing an alcohol level between 60-80%.  Many gels are thickened with Carbomer or an acrylate variant such as Acrylates/C10-30 Alkyl Acrylate Crosspolymer.  Due to the high level of alcohol in these formulations, the use of sodium hydroxide to neutralize Carbomer is generally not suggested. Typically, it is recommended to neutralize acrylates polymers with organic amines.  Formulators have used triethanolamine, aminomethyl propanol, and tris amino.  The use of acrylates in making the gels provides a good cost advantage and helps create crystal clear gels.  The formulations typically crumble during rub out due to the inability of acrylates to handle residual salt in hands.  Due to recent attacks on acrylates from various organizations and their potential labeling as micro-plastics, many formulators switched to cellulosics as rheology modifiers.  Cellulosics are naturally-derived and can thicken alcohol-based formulations as well.  The most commonly used thickener is hydroxypropylcellulose followed by hydroxyethylcellulose.  Cellulosics will yield transparent gels and will impart a slip to the formulation.  Cellulosic gels do not need to be neutralized and do not crumble in hands upon rubbing.

Alcohol-free hand sanitizers typically capture a small slice of the market by targeting some customers that prefer not to use alcohol.  These products are based on Benzalkonium Chloride and come in various forms like emulsions, gel-creams, and gels as well.  Due to the absence of alcohol these products could be considered Halal if they meet the rest of the criteria necessary for certification.

A myriad of ingredients can be typically added to hand sanitizer gels.  Glycerin is very popular as it helps moisturize the skin and changes the feel and application of the gel as well.  Aloe is another ingredient commonly added to the formulation due to its well-known healing and soothing properties.  Several alcohol-soluble esters have been used as well.  Esters of alpha-hydroxy acids are popular due to their high polarity and ease of incorporation into such formulations.  Such esters are lauryl lactate, myristyl lactate, and C12-15 alkyl lactate.  Other alcohol-compatible esters with high polarity include diisopropyl adipate, and isodecyl neopentanoate.

One important key ingredient present in most gels is the fragrance.  Selecting a fragrance for a hand sanitizer is not quite simple.  One must make sure that the fragrance is stable at such high level of alcohol for the duration of the accelerated stability (typically, 3 months at 45°C).  In addition, the fragrance must cover the alcohol odor without being overwhelming since many professionals apply the product more than 10 times a day.

When checking the stability of such formulations, one should not forget to store them in explosion-proof ovens.  These formulations are quite flammable, and if stored in a regular laboratory oven can cause a fire hazard.  The compatibility of these formulations with the final packaging should also be tested as the high level of alcohol could deform many types of plastics.

I hope this quick review of hand sanitizer formulations is quite helpful for formulators and would give them a head-start when formulating such products. Now it is up to the individual formulator to be creative and add his/her personal touch to make such formulations unique in this crowded undifferentiated market.

References

  1. Federal register/Vol 81, No. 126/Thursday June 30, 2016 – 21 CFR Part 310
  2. Federal register/Vol 82, No. 243/Wednesday December 20, 2017 – 21 CFR Part 310
  3. Federal register/Vol 84, No. 71/Friday April 12, 2019 – 21 CFR Part 310
  4. Temporary Policy for Certain Alcohol-based Hand Sanitizer Products During the Public Health Emergency (COVID-19) Guidance for Industry. March 2020, Updated Feb 10, 2021

 

Dr. Fares started his career in personal care studying the effect of solvents on sunscreen chemicals.  His interest in skin drug delivery especially from polymeric matrices grew during his graduate work at Rutgers, where he received his Ph. D.

Dr. Fares worked at Block Drug and GlaxoSmithKline where he held positions in research and development in the areas of skincare and oral care.  After that, he joined L’Oreal where he held several positions of increasing responsibility leading to AVP of skincare.  He is currently the Senior Director of skincare and oral care at Ashland Specialty Ingredients.  Dr. Fares is the author of many publications, and patents and made many presentations in national and international meetings in the areas of suncare, skincare, and oral care.  Dr Fares chairs the NYSCC scientific committee and has won multiple awards in the area of sun care and polymer chemistry.

The Holistic View of Beauty

by james.runkle@drummondst.com james.runkle@drummondst.com No Comments

Introduction

Back in 2000, when I started my adventure as a cosmetic scientist and formulator working at a contract manufacturer, I was introduced to suppliers and brands that suggested ingestible ingredients as an effective treatment to improve the way our skin, hair and nails looked. We called it at the time the “inside-out” approach to beauty. Although I knew about the association of certain vitamins with skin and hair aspect and quality, the supplements were more complex, from collagen to carotenoids to different phytochemicals with issues related to release, stability, bioavailability, etc.. Mostly because the lack of sufficient clinical evidence and the challenge for suppliers operating in the cosmetic industry to support clinical trials addressing the inside-out approach, many of these ingredients went unnoticed in the bigger picture of beauty and made their way through the nutraceutical market with a certain success, focusing on general wellbeing or wellness. Back in the day, I believed that the predominant dogma of addressing skin care and hair care as a specific target using topical products, almost like skin and hair were disconnected from the rest of our body, slowed down the adoption of a more holistic approach, and the idea to address beauty through an inside-out intervention as well.

A Holistic World

The holistic view of our body has been explored and developed for thousands of years in TCM and Ayurvedic Practice and represents a philosophy of life. We are looking at interactions and equilibrium between our senses, our organs and our external world with its colors and smells, but also with its dangers (pollution and stress in all their form). The notion that we are completely connected as individuals and with the environment is not surprising either. We just lived the disconnect for too long. There is a willing to reconnect to ourselves, our communities and nature. Sounds familiar? This is very much in line with the principle of sustainability, but also with a holistic view of the world where individuals function better as communities. Connections are complex though and not necessarily linear. This is why it is risky to simplify; but in general, we can draw some essential concepts that I think are main takeaways when approaching the skin and hair as part of our body and subjected to its rules.

The Scientist View

First, embryology studies taught us that some organs derive from the same embryonic tissue. When we think about the brain, skin, hair connection we realize that all these organs are derived from the same ectoderm layer during embryogenesis. Although these organs eventually differentiate to assume morphology and function completely different from each other, they do share mechanisms and pathways that are similar and interconnected. Some years ago, this basic understanding allowed scientists to develop concepts around the so-called neurocosmetics or the brain-skin-hair- axis.1,2 These concepts are becoming more prevalent these days since they are helping us to understand how stress and our mind influence our body and our appearance. When stress, either internal (psychological) or external (environmental), hits us, it definitely has an impact on how our skin and hair looks. Although it is common sense, since we have experienced it in the past either ourselves or seeing on other individuals, science is helping now connecting the dots between stress, related neurotransmitters and a physiological change ultimately associated with a condition and/or an appearance (looking good or looking bad).

The Intimate Connection

Stress has been part of my life earlier on (Buddhism believes that since stress or trauma starts with birth and never really goes away, we spend our lifetime to figure out how to reduce it or alleviate it with a goal of trying reach a more balanced, happy state) and I am pretty sure that some of the specific pain I felt in some parts of my body when I was younger were created by my brain: also called a psychosomatic state. I am sure it may have happened to some of you. We generally believe that our mood can influence our organs holistically. There are publications suggesting how a positive or a negative predisposition can affect a condition, even a very serious condition, with the body releasing certain hormones. But what about the skin or the hair and how our mood or senses-related stimuli can affect our look? It was not until reading some articles published in the late 90s by Prof Paul Bigliardi, that I realized that even the skin can change physiologically based on the influence of neurotransmitters (including our very own and not just CBD…). The discovery by Paul of opiate receptors carried deep in the dermis by tiny neuro-fibers was groundbreaking.3 And the intimate connection between these receptors, the transmitters and skin thickness!4 More recently, the presence of smell receptors in the skin and hair triggering physiological changes.5-6 Can our senses change our skin appearance? Probably yes… And what about our hair look and growth? Some recent work is evidencing how the hair follicle and dermal papilla cells can be directed to arrest growth by corticosteroids related molecules,7,8 and how mediators like Cortisol and Cortisol spikes can determine the way our hair grows or sheds.9 We have clinical evidence that by supplementing our body with phytochemical-based supplements we can change the way our hair and skin look.10,11 There is a bigger picture, which as cosmetic scientists we need to consider when creating cosmetic products for skin and hair, and this is our inner self.

Conclusion

Our body is one and our beauty depends on how we treat our body. Nothing deeper than that. Recent scientific discoveries explain how our senses are contributing to our appearance. We investigate how different ingredients, either applied topically or ingested, can help us maintain a healthy body and healthy look. The future is holistic, and science is now on our side!

References

  1. Theoharides TC, Stewart JM, Taracanova A, Conti P, Zouboulis CC. Neuroendocrinology of the skin. Rev Endocr Metab Disord. 17(3):287-294, 2016
  2. Paus R. Exploring the “brain-skin connection”: Leads and lessons from the hair follicle. Curr Res Transl Med. 64(4):207-214, 2016
  3. Bigliardi PL, Bigliardi-Qi M, Buechner S, Rufli T. Expression of mu-opiate receptor in human epidermis and keratinocytes. J Invest Dermatol. 111(2):297-301, 1998
  4. Neumann C, Bigliardi-Qi M, Widmann C, Bigliardi PL. The delta-opioid receptor affects epidermal homeostasis via ERK-dependent inhibition of transcription factor POU2F3. J Invest Dermatol. 135(2):471-480, 2015
  5. Ho HK, Bigliardi PL, Stelmashenko O, Ramasamy S, Postlethwaite M, Bigliardi-Qi M. Functionally expressed bitter taste receptor TAS2R14 in human epidermal keratinocytes serves as a chemosensory receptor. Exp Dermatol 30(2):216-225, 2021
  6. Jimenez F, López E, Bertolini M, Alam M, Chéret J, Westgate G, Rinaldi F, Marzani B, Paus R. Topical odorant application of the specific olfactory receptor OR2AT4 agonist, Sandalore® , improves telogen effluvium-associated parameters. J Cosmet Dermatol. 20(3):784-791, 2021
  7. Dell’Acqua G, Richards A. Human hair follicle dermal papilla as an in vitro model to study stress-induced hair growth arrest. J Invest Dermatol, in press, 2021
  8. Ito N, Ito T, Kromminga A, Bettermann A, Takigawa M, Kees F, Straub RH, Paus R. Human hair follicles display a functional equivalent of the hypothalamic-pituitary-adrenal axis and synthesize cortisol. FASEB J 19(10):1332-4, 2005
  9. Anzelone M, Richards A, Dell’Acqua G. Stress-induced hair loss benefits from a standardized nutraceutical. Naturopathic Doctor News & Review, May 2020
  10. Ablon G, Kogan S. A six-month, randomized, double-blind, placebo-controlled study evaluating the safety and efficacy of a nutraceutical supplement for promoting hair growth in women with self-perceived thinning hair. J Drugs Dermatol. 17(5):558-565, 2018
  11. Granger C, Aladren S, Delgado J, Garre A, Trullas C, Gilaberte Y. Prospective Evaluation of the Efficacy of a Food Supplement in Increasing Photoprotection and Improving Selective Markers Related to Skin Photo-Ageing. Dermatol Ther (Heidelb). 10(1):163-178, 2020

After obtaining his PhD in Cell Biology in 1989, Giorgio Dell’Acqua worked for 15 years as an investigator in applied medical research in different institutions including Mount Sinai Medical School in New York and Harvard Medical School in Boston. Moving to the private sector in 2000, he has spent the last 20 years as an executive and cosmetic scientist in the personal care industry. As a consultant, he directed R&D, Science, Product Development and Innovation at contract manufacturers, brands and ingredients companies, specializing in skin and hair care applications. Giorgio Dell’Acqua has helped bring more than 200 successful active ingredients and formulations/products to market, has authored more than 70 publications in medicine and cosmetic science, he is an inventor in many patents, and has been a presenter and a keynote speaker in more than 20 events and conferences in the last 2 years. Some of his recent product development activity has focused on upcycling, prebiotics, adaptogens, clean beauty, and social progress in sustainability. Giorgio Dell’Acqua is an award-winning speaker on natural ingredients and a regular writer on sustainability. He is also the 2021 Chair- Elect for the NY Chapter of the Society of Cosmetic Chemists and its blog producer.

Formulating mineral sunscreens for people of color

by james.runkle@drummondst.com james.runkle@drummondst.com No Comments

Although it seems to be common sense and even routine to some consumers to use sunscreens to protect the skin from the harmful effects of the sun, many still do not use any sunscreens in America.  This is especially true in the BIPOC (Black, Indigenous, and People of Color) community.  As the demography in USA has become more diversified over time, many cosmetic brands have recognized the needs of consumers of diverse skin tones.  In recent years, there has been a push to wear sunscreen for this BIPOC demographic.

Among many reasons for the lack of use of sunscreens in this demographic, aesthetics and safety of sunscreen products are most worth noting.   For decades, organic sunscreens have been dominating the sunscreen market. They could be irritating to sensitive skin and sometimes sting the eyes.  There has been a shift in recent years to the use of inorganic UV filters due to several reasons:

  1. Mineral based ingredients are deemed to be inert, sustainable, and well associated with personal wellbeing.
  2. ZnO was approved in 2016 as a safe and effective sunscreen active in EU
  3. More importantly, TiO2 and ZnO are the only two actives assigned with GRASE status by FDA in its 2019 proposal1.

However, formulating mineral sunscreens for consumers with dark tone, especially skin types V and VI on the Fitzpatrick scale, has remained a challenge. As it can be imagined, the major challenge to consumer acceptance is whitening or white cast on skin after application. This is because inorganic UV filters are particulate materials with high refractive index, and thus, can scatter the visible light strongly.

Although material technology has much advanced to allow TiO2 and ZnO particles to be made as small as 10 – 20 nm and highly transparent on light skin types, whitening and/or bluing on very dark skin remains problematic for sunscreen formulators.  Below, will review a few formulating strategies for mitigating this undesirable side effect.

 

Use ZnO only

ZnO has a refractive index of 2, much lower than rutile TiO2 which has a refractive index of 2.7. According to Mie’s theory on scattering, light scattering by ZnO is just about one third that of TiO2, meaning it is much more transparent. Use of TiO2 even at a low level could spoil the aesthetics. Therefore, it is imperative to use ZnO only for dark skin tones.

There are many grades of ZnO powder on the market with primary particle sizes in the range of 20 – 300 nm. Obviously, the smaller the size, the higher the transparency. For dark to very dark skin tones, a primary particle size in the range of 20 – 30 nm should be used.

ZnO is a moderately effective UVB sunscreen active, and thus, is often needed at very high level (15 -25%) to achieve SPF 30 or higher.  Such high use level presents another reason why a very small particle size must be chosen to maintain high transparency.

There are many ZnO-only sunscreen products marketed for consumers with dark skin types especially African American. One example is On-The-Defense Sunscreen SPF 30 from Eleven by Venus Williams. It contains 25% ZnO and claims “Sheer mineral sunscreen that melts onto skin, leaving a semi-matte, non-chalky finish.’

 

Disperse ZnO powder well

Just finding a ZnO with a small primary particle size does not mean a complete solution yet.  ZnO particles at this size scale have a very large specific surface area and surface energy and tend to aggregate heavily.  In reality, what really interact with the light are the aggregates or even agglomerates.  Therefore, proper dispersion to remove or minimize the population of large aggregates is important. Keep in mind, a small portion of large particles play a significant role in scattering visible light (whitening) due to their relatively large mass.  While dispersing ZnO with high-speed mixer or homogenizer may be sufficient for skin type I to IV, milling ZnO powder using a bead mill is necessary for higher transparency requirement.  In the absence of an efficient mill, the use of a ZnO pre-dispersion is a simple and effective approach.

 

Mitigating Whitening/Bluing

At high use level, ZnO will show some whiting on skin types V and VI even when it is very fine and well dispersed.  Moreover, even if the whitening is made unnoticeable, scattering of light in the range of 380 – 450 nm cannot be avoided, leading to bluing.  To mitigate the whitening/bluing and make sunscreen blend into dark skin well during application, pigments of warm colors can be used, as follows:

  1. Red iron oxide pigment

The red color of typical iron oxide pigment used at a level of 0.2 – 1.0% is able to neutralize ll the whiteness and bluing of ZnO sunscreen. Many mineral sunscreens tinted with red iron oxide are available on the market and are marketed for ethnic skin style.  However, red iron oxide pigment is highly opaque, and its texture on skin can be chalky. When it comes to skin type V and VI, the finish with such pigment just cannot be as natural as consumer would expect.

  1. Transparent iron oxide pigments

Transparent iron oxides are an improvement from standard iron oxide pigments and were initially developed for varnish formulation. They typically have a primary particle size of < 30 nm and are as transparent as nano ZnO. Boots Co. PLC first disclosed the use of nano red iron oxide in inorganic sunscreen formulation in the early 1900s2. A few premium brands started to use both transparent red and yellow iron oxides in their daily wear sunscreen products since the mid-1990s. However, the use of such pigments remained very limited to this day.  In addition to high cost, one technical hurdle is that transparent oxides are very difficult to disperse. With this in mind, I highly recommend the use of a pre-dispersion.

Typically, 0.2 -0.5% of transparent red is sufficient in an all-ZnO sunscreen formulations.  Because dark skin can have different undertones (red, yellow or grey, etc.), a combination of transparent yellow and red iron oxides provides a more complete solution. At this use level, the transparent iron oxides impart almost no texture to the skin, and the finish is completely natural.

  1. Use of Earth tone or dark pearl pigments

The basic optical principle of using Earth tone pearl is similar to using iron oxides.  As we know, pearl pigments often refer to mica with layers of metal oxide coating.  They usually have good transparency, especially when the substrate is highly pure synthetic mica.  As a result, its finish on the skin can be much more natural than a typical red iron oxide pigment.

It is preferred that pearls have red iron oxide as coating and that their particle size be below 15 microns. Any larger size may generate a pearlescent sheen on skin that will be deemed unnatural.  Typical use level is about 0.1- 1.0 %.  For very dark skin, grey or dark pearl pigments with a coating of black iron oxide or a combination of red and black iron oxides can be used at a level of 0.05 – 0.5% for further adjustment.

Like transparent oxides, a blend of Earth tone pearl and dark pearl pigments will provide a good balance for dark skin types with various undertones.  Formulators at Kobo Products applied this technology to its 4 in 1 Multi-Purpose Sunscreen Cream and won CEW Award in 2019 for the category of Ingredient and Formulation3.

  1. Use of SPF boosters

The direct way to reduce whitening is to reduce the use level of ZnO.  It can be done by selecting the right SPF boosting agents.  Below are some strategies presented in the 2015 Sunscreen Symposium4. Here are a few highlights:

a) Film former: This technology is well known in our industry. Film formers can be oil soluble, water soluble or water dispersible (like latex). Many have been shown to boost SPF by 20% or more.

b) Antioxidants/anti-inflammatory: Many of them are proven to suppress the generation of erythema and can boost SPF very effectively.

 

Conclusion

Formulating mineral sunscreens for skin types IV to VI requires special considerations for very high transparency. An all zinc formulation should be the first consideration. The use of transparent oxides, and a blend of Earth tone pearl pigments can help to further reduce the whiten and/or bluing of sunscreens on dark skin tones and make them blend into skin more naturally.

 

References

  1. https://www.federalregister.gov/documents/2019/02/26/2019-03019/sunscreen-drug-products-for-over-the-counter-human-use
  2. NA Fardell et al., EP 0616522: Sunscreen compositions
  3. https://www.cew.org/award/4-in-1-multi-purpose-sunscreen-cream/
  4. Y Shao et al., Practical tools for boosting sunscreen efficacy, Sunscreen Symposium 2015

 

Acknowledgements

The author is grateful to Tatyana Tabakman and Cheres Chambers for insightful and helpful discussions.


Dr. Yun Shao joined Kobo Products Inc. in 1996 and currently serves as the vice president of R&D.  He has over 20 years of experience in micro TiO2 and ZnO development and in inorganic sunscreen technology and regulations.  He is also experienced in pigment surface treatment, wet grinding, specialty cosmetic ingredients, color cosmetics and global cosmetic ingredient regulations. He has presented his work in various scientific conferences including IFSCC congress and FLSCC Sunscreen Symposium.  Dr. Shao holds 8 patents. He has co-authored several chapter books and technical papers on surface treatment and inorganic sunscreen formulations. Dr. Shao earned his Ph.D. in Polymer Chemistry from Rensselaer Polytechnic Institute and his B.S. in Applied Chemistry from University of Science and Technology of China.  He is the founding member of Chinese American Cosmetic Professional Association and the President during 2011-2012. He is also member of Society of Cosmetic Chemist and Chinese American Cosmetic Professionals Association and Tristate CACS. Dr Shao joined the NYSCC Scientific Committee in 2020.

Challenges in Cosmetic Formulation

by james.runkle@drummondst.com james.runkle@drummondst.com No Comments

Formulating cosmetic products presents many challenges, ranging from regulations, product safety, performance, aesthetics, consumer demographic trends and claim substantiation, in addition to media scrutiny, etc.  To be a successful formulation chemist, one must toggle many priorities with limited resources of time and money, while maintaining market launch timing.  In this blog, a few of the selected challenges will be discussed.

Every Ingredient Should Have a Function.  A formulation chemist should understand the structure-property relationship and the role of each raw material in a formula.  Raw materials are tools for creating formulation options and contributing to tactile sensory, stability and efficaciousness of the formulation.  There are many cosmetic ingredients with multiple functions, providing benefits that meet consumer demands.  By understanding the ingredient function and interactions in the complex composition, chemists can develop better formulation strategies.  At times, a formulator would be asked to “tweak” an existing formulation in order to replace an ingredient in response to a supply chain issue, regulatory constraints or to meet some sensory needs requested by marketing or consumers.  Simply piling ingredients into a formula does not always provide a solution to the problem.  In fact, it can backfire and create instability, or other unwanted issues.  It is important to be familiar with the latest raw material technology by developing long-term partnership with strategic teams (both internal and external contacts).

How to Knockoff a Cosmetic Formula?1 One way to quickly become familiar with a cosmetic formulation is to “knockoff” (or duplicate) an existing formula.  Perry Romanowski published a 10-step strategy to essentially “reverse engineer” a competitor’s formulation.  This is by no means to simply create a “me-too” product, but to thoroughly understand formulation strategy and applications of raw material technology developed by competition.  It should serve as a good practice point for a novice and sometime even a seasoned formulator.  Again, the key points in Perry’s method are to (1) understand raw materials used in a formula by studying its full ingredient list (FIL), (2) read competitor’s patents and publications, and last but not least (3) create, revise and test prototypes, until the desired aesthetics are obtained.

Formulating Existing Formulation Platform.  As mentioned, a cosmetic formulator could be asked to “reformulate” an existing product formulation.  This is typically for continuation of a franchise with small modifications to the marketed formula, or a product launch with new claims, albeit based on existing formulas.  This approach can, for the most part, save time and resources on efficacy and safety testing, in addition to minimizing the potential risks from regulation and/or right-to-market.  Tony O’Lenick describes, in his many publications, “controlled modifications” of existing formulation. It is achieved by: 2 (1) minimally disruptive technology, and (2) functional formulation.  The first approach uses low concentrations of polymeric surfactant(s) to alter aesthetics of existing formulation.  The second strategy pertains to raw material replacement in a formula, i.e., replacing raw materials based on how they function in the formulation.   For certain formulation types, especially mass-market products, it is also imperative to make certain of cost effectiveness for the final formulation.

Developing New Formulation Chassis.  This brings the most challenging and rewarding experience for a formulator, i.e. to create a brand new formulation chassis with a new formulation composition that gives rise to new and enjoyable consumer use experience.  However, the challenges for formulators exist in many areas: (1) developing a stable formula with a plausible right-to-market, and more excitingly, new patent opportunities in the IP landscape, (2) meeting the microbiological, safety and regulatory requirements for the specific product launch markets, (3) achieving efficient scale-up production from laboratory bench experience, and for sustainable business sake, (4) meeting the consumer demographic trends and marketing needs, including claim substantiation and consumer communication, etc.  Due to these multifaceted challenges, this type of formulation is typically managed as a longer-term research project.

Product Performance and Sustainability from a Formula Perspective.  Long before the pandemic of 2020, the personal care industry has seen the rise of “clean beauty” demand from consumers, while the pandemic seems to have accelerated this demand.3  By definition, “clean beauty” product formulation requires the use of safe and non-toxic ingredients with proven efficacy.4  To take it further, we shall take into consideration sustainable development, in order to counteract global warming and environmental changes.4,5  What does it all mean for a cosmetic formulator?  It begins with selection of bio-based, renewable ingredients with respect of biodiversity and societal equality, and minimizing the use of fossil-based, non-renewable raw materials.  During formulation stages, one must also bear in mind the potential water usage to minimize the water footprint, and incorporation of as much as possible energy-efficient process for scale-up during production.6

Conclusion  

Cosmetic formulation has the most exciting challenges in combining science and art in response to the unmet needs from consumers.  A formulation scientist is an artist that creates new textures and influences the sensory perception of the customers.  In this ever-changing world of cosmetic and personal care industry, formulators are the primary driving force of technology and innovation.  No matter what formulation challenges at hand, product performance and sustainability will undoubtedly be the future of cosmetic formulation.

Acknowledgements

The author would like to thank the kind review and comments from Giorgio Dell’Acqua, Hani Fares, Ben Blinder, Howard Epstein, Hy Bui, Ryuji Hara and Ronni Weinkauf.

References:

  1. Perry Romanowski, https://chemistscorner.com/
  2. Tony O’Lenick, http://www.scientificspectator.com/tony-olenick-compilation-of-articles/
  3. NYSCC “At Home Live Series – Clean Beauty”, November 19, 2020.
  4. Giorgio Dell’Acqua, Clean Beauty – Beauty Horizons, December 15, 2020 https://digital.teknoscienze.com/beauty_horizons_1_2020_ww
  5. L’Oréal Sustainability Commitment for 2030. https://mediaroom.loreal.com/wp-content/uploads/2020/06/EN_Booklet_LOreal-for-the-Future_2020.pdf
  6. L’Oréal Product Environmental & Social Impact Labelling Methodologies. https://www.loreal.com/-/media/project/loreal/brand-sites/corp/master/lcorp/documents-media/publications/loreal-pil-methodologie-en01.pdf

Dr. Catherine Chiou holds a BS degree in Chemistry from National Taiwan University and a Ph.D. in Bioinorganic Chemistry from the University of Minnesota.  Catherine’s NIH Postdoctoral fellowship training in Synthetic Chemistry took place at Harvard University.  Her first industrial position was with Unilever Research US in the laundry bleach research program and machine dishwashing detergent research, including I&I applications.

Catherine began her career in cosmetic field at L’Oréal USA in 2001 in the DIMP (International Raw Materials Department).  She worked on all aspects of “innovative raw material” functions, including scouting for new supplier innovations, and managing supplier relationships.  In addition, Catherine took on a role within the PCPC INCI Committee.

Catherine is currently an Associate Principal Scientist at L’Oréal USA in the Cosmetic Application Domain, focusing on developing skin cleansing and makeup removing technologies.  Prior to the current position, she has worked in the skin care research and innovation lab as a senior formulator, contributing towards development of platform technologies and several global launches of skin care treatment products.  She is an inventor for more than 20 US and international patents.

How Many Languages Does our Skin Speak?

by james.runkle@drummondst.com james.runkle@drummondst.com No Comments

How Many Languages Does our Skin Speak? A fresh look at what it can it teach us in terms of innovation if we listen.

Inflammation is Just the Beginning:

Inflammation has garnished the attention of mainstream headlines for the past 20 years and has certainly taken center stage describing and managing the current virulence of the pandemic.  With terms like cytokine storm, pre-existing conditions and co-morbidities, what have we learned and what we still need to learn to properly manage the ill effects of inflammation and its impact on health is astounding.  As a biologist, I adopted the general tenant that inflammation is the root of all evil when it comes to aging and disease, particularly in the skin.  Whether its role is in normal aging from a subclinical perspective or pathological in nature in an acute verses chronic situation, inflammation seems to be a rate limiting step or first domino to fall for most underlining causes of both intrinsic and extrinsic aging processes in our largest organ the skin.  Even in the Covid-19 era, we are seeing persistent skin rashes documented post infection, why?  What are we doing right and what should we be doing different?

The good news is that we seem to understand inflammation from a mechanistic point of view.  How reactive oxygen, metals, lipid mediators, enzymes, transcription factors, temperature, microbes and sun play a role in skin inflammation is well documented.  The disconnect here is that we in the industry of cosmetic science have decided to treat the sources of inflammation as individual events rather than a consortium of cumulative ever changing processes designed to mute our first line of defense.  This is akin to putting a lock box around a fire alarm verses reducing existing fire hazards.

In this regard, let us not loose site of the purpose of inflammation, which is to alert and respond to acute threats to homeostasis or skin balance.  Every level of our biological organization has its own cadence on how homeostasis is maintained and managed over time.  From a molecular level, through soluble cytokines (the language of our cells) all the way to behavior responses, evolution has afforded us a great deal of redundancy in this regard, all culminating to the ultimate goal of maintaining health and balance.  In what follows, I hope to serve up a fresh look at how we as skin care technology providers can approach new product designs and formulation innovations that not only address acute disturbances in skin but may ultimately change the way we look and feel about our skin and ourselves as a whole.

The Skin as a Sensory Organ:

The best part of focusing on the skin is that it does so much for us in terms of our survival, health, and our ability to adapt to the environments we find ourselves in on a daily basis.  Furthermore, the epidermis and some of the cell types that reside in it (melanocytes, Langerhans-like phagocytes) are embryologically derived from ectoderm which also gives rise to our nervous system proper.  This is a profoundly underappreciated opportunity as our skin has all of the “gear” needed to effectively communicate with the nervous system as well as the endocrine system and vice versa.   In this regard, we need to integrate the fact that our neural, endocrine, immune, skin microbiome and skin biology are all interlaced and cross talk every moment of our existence.  The ability of our skin to react to its environmental threats through inflammatory processes has opened a window into a world that is vastly more complex and interactive.   It requires a master’s degree in linguistics to hear all the talk between keratinocytes, immune cells, hair follicles and sweat glands and melanocytes.  As a result, this conceptual understanding opens up targets that not only affect the skin proper but our behavior as well.  What if we could understand the autonomic picture our brain has of our skin?  I believe we would see numerous snap shots of skin grafts unique to one another, painted by skin thickness, pH, lipid structure, water content, hair follicle density, immune residence and microbiome attendance.  Could we re-focus our formulation efforts in terms of sensory to be more inclusive of these micro environments and their associated biology?  Could we change the way our brain “sees” our skin?

 

Behavior is driven by how we perceive our surroundings.  Our skin is considered a neurosensory organ much the same way other species use antennae or chemoreceptors to “see” their environment as demonstrated by insects and snakes respectively.  Our skin senses electromagnetic radiation, temperature, chemicals, pH, biological insults, and subtle changes in our microbiome.  It also knows when there are sub clinical changes in chemistry as well as disruptions in barrier and wounding.  All of these stimuli we cannot see with our other senses unless they are out of sync or control.  We tend to focus more on sight and sound as an organism.  Why then do we ignore the largest sense organ we possess when it has so much to say?  More so, all of these stimuli are transmitted to the brain (consciously or unconsciously) and to the surrounding cells and tissues simultaneously, thus having an impact not only on our behavioral responses but on our epidermal biology, our immune and endocrine systems.  Furthermore, the reverse is true.  The brain and adrenals along with the immune cells talk back.  A fundamental requirement for communication is that more than one entity needs to deliver information to another that can receive and react to it.  How cool is it that whatever stimuli the skin observes it is translated via different systems that act in concert to maintain homeostasis and dictate behavior.  As formulators and inventors, the next level of innovation will come from exploiting these lines of communication.  Recall how simple the Wright brother’s solution to flight was compared to the latest version of air travel today.  You will most likely not be in a position to imagine a jet airliner if you never saw the Kitty Hawk.

Immune System Integration:

If things were not complex enough, we need to consider the immune system and all of its abilities and functions as a driver of skin health.  The marvelous thing about our immune system is that it is driven not just by genetics but also by environmental pressures we expose our body to on a regular basis.  The immune system adapts and learns and has a periodicity that is defined by age and time.  Our immune functions start out naive then grow, mature, plateau and decline throughout our lifespan.  Furthermore, our immune system is organized into two systems (innate and adaptive/learned) that together synergize in function.  It even has its own residential lymphoid cells called skin associated lymphatic tissue or SALT which supervises and coordinates your interactions with all things non-self.  From that organization it specializes in various modalities of responses that are classified into 3 groups depending on the type of initiation involved and cytokine profile released into the milieu along with contributions from epithelial cell derived cytokine signals such as IL-33.  For example Type I immunity is relegated to intracellular threats (viruses and parasites) and the production of IFN-g and/or TNFα.  Type 2 immune responses are in ordinance with itch and are caused by harmful substances driven by the secretion of IL-4, IL-5 and IL-13.  Type 3 immunity is specific to extracellular bacterial and fungal infections and characterized by the production of IL-17 and IL-22 cytokines.   It is interesting to note that the cytokine profiles of each type of immunity dictate a specific ordered response by immune tissue, but they also modulate sensory perception and behavior, another key component to our overall host defense arsenal.  For example, IL-33 release from keratinocytes in a compromised epidermal barrier can stimulate local neurons to become hypersensitive and hyper-excitable, thus releasing neuropeptides like substance P and CGRP, which then feedback on the very same keratinocytes to increase their proliferation in an effort to restore the compromised barrier.  As a result, the hypertrophy can further disrupt epidermal differentiation, trap bacteria and acne and/or folliculitis ensues respectively in affected sebaceous gland canals and hair follicles respectively.  Furthermore, antibodies to IL-13 and IL-4 (type 2 immune responses) reduce barrier inflammation which reduces itch in AD stuffer’s.

By grouping immune type cytokine profiles together along with their temporal expression patterns that includes initiation, plateau and resolution makes for a more precise technology development strategy in this regard.

 

A Systems Approach to Understanding:

It is an interesting to note that the nervous system and its functions rely on afferent signals (sensory neurons and their associated stimuli) to understand its place in the environment, whereas the immune system also “senses” our body’s interactions with our surrounding through more of a military surveillance strategy of touch, chemical codes, catabolism and synthesis.  Furthermore, the brain and its neurons are fixed in place converting chemical signals into electrical and back again at supersonic speed whereas the immune system is both static and dynamic adapting and learning at a significantly slower pace alongside the brain.  It evolves and grows.   The interplay between both of these systems tends to out rank the local tissue signals in which they reside. A linear approach to skin therapy has focused primarily on the residential populations of the skin with a peripheral mention of the other systems as secondary is like only listening to one side of the conversation.  Leveraging a systems approach to new skin therapeutics and personal care technologies could lead to significant transformational innovations in product development including new categories of skin care.

 

 

How does all of this work and where are we headed? 

Advances in sensory biology (specifically itch and pain) have elucidated novel mechanisms that arose from our understanding of inflammation.  Itch and pain are great examples of behavior changes as we have all experienced both.  What if by understanding how to modulate these behaviors we could apply these same strategies to resolve dry skin, alter tone and texture, improve radiance and create the de-novo synthesis of endogenous beneficial molecules such as vitamin D, melanin and keratin.  Furthermore, what if we could take these strategies forward to build better nails and hair, modulate sebum quality and quantity and even provide some level of subconscious behavior that could help you lose weight, reduce stress or just be happier?  We spend a lot of time and energy trying to reduce acne which has significant behavior ramifications especially in teenagers, when in actuality, if we could just reduce the erythema in a timely manner, most of the terrible downstream problems would be better tolerated or ameliorated such as post inflammatory hyperpigmentation and self-esteem related syndromes.

Melanocyte Biology Reimagined:

Since melanocytes are the focal point of Post Inflammatory Hyperpigmentation, they could be considered the “conductor” of the cross talk between residential skin cells, neurons and immune processes.  These cells that act as a UV detectors in our skin may in actuality have the ability to sense and focus on other stimuli.  They are of course derived from the same primordial soup as neurons.  If true, these master regulators would need to communicate with and receive signals from all cell types including neurons, macrophages, Langerhans cells and various lymphoid tissues (SALT).  Just like neurons, melanocytes convert energy to communicate.  Here melanocytes convert electromagnetic energy (UV and HEV) into relevant biological signals that initiate signal amplification and recruitment of multiple tissues to ultimately elicit a behavior change.  The same signaling molecules that have a role in the central and peripheral nervous tissue also have a role in cutaneous melanocytes. These include signaling pathways that include Wnt, bone morphogenetic proteins, endothelins, hepatocyte growth factor, fibroblast growth factors, and neurotrophins.

Applying the Concepts:

When afferent sensory neurons fire in our skin, they release neuropeptides in an efferent (reciprocal) manner that has its effects on melanocytes and immune cells simultaneously.  In other words, the skin is already reacting to the stimuli before the brain even gets the signal.  This is an important event as this profile of cellular signals creates a customized code of signals unique to the stimuli, very similar to the basic formula for how your brain remembers a memory.  If by understanding this profiling technic our body uses on the local level we could indeed teach our skin to react in different ways by nudging and modulating profile dynamics.

This concept is already in practice through the use of antibody therapy for psoriasis and atopic dermatitis (AD).  These antibody therapies work by interfering with the cytokine-induced pathways in neurons, important for intercellular conversations with local cytokines which then in turn modulates itch and inflammation.  The immune therapeutic Tofacitinib works through JAK inhibition thus reducing inflammation better than traditional broad spectrum anti-inflammatory strategies (systemic steroids).   Here the traditional modality of treating the source of the problem is over ridden by muting the signal that helps propagate it.  Additionally, this neuron targeted approach is also supported by the observations that patients with inflammatory (AD) experienced resolution of inflammation in body parts that experience nerve loss.  What are we to conclude from this? Chronic inflammation requires communication with the nervous system.

Integration of the Skin Microbiome:

Peeling back yet another layer of the onion, we need to include our newfound tribe the skin microbiome.  In collaboration with the gut microbiome, these two tribes have considerable influence on everyday life as it relates to well-being and health.  If you wonder of their overall purpose, it lies in their ability to adjust tolerance and direct the necessary “activation energy” needed to amplify inflammation, over and above the status quo.  Think of it as immune exercise or conditioning.  The diversity of microbes in and on our body translates and cross-trains all the different biological conversations between the skin epithelia, immune cells and processes along with the existing neural architecture. The “chatter” establishes a level of readiness.  It results in an overall host defense that is primed and semi-activated to address danger and invasion.  When microbiome diversity is lowered or dominated by a few select species, the response is detrimental by two-fold.  One, it allows for re-colonization of the skin by opportunistic invaders which may not be pathological at normal levels but create that cytokine profile or “storm” that trips the balance of cross talk between all the players resulting in an increase in entropy of the whole system.  Chaos, isn’t that what we all work so hard to control?  Two, the low diversity establishes a lower state of readiness and as result the conversations become quieter and limited leaving the health of the skin vulnerable to imbalance and thus, putting negative pressure on behavior.  Can we blame our little friends for our actions and thoughts?  Absolutely!  Just as folks with AD, psoriasis, irritable bowel syndrome and Crohn’s disease.

In closing:

As a result of all this biological chatter we have order and purpose.  It is exciting to see how fundamental understanding evolves.  The integration of multiple languages into a new one with higher purpose, efficiency and meaning is an evolutionary learning process.  To naively think we understand the language of our biological complexity is limiting our potential.  We must integrate and transcend across the mechanistic understanding and incorporate a multi-disciplinary approach to new concepts and ideas.  We need to explore new ways to achieve desired responses and ultimately behavior that favors well-being for all ages and health both physically and mentally.  I can’t help but wonder how many times we find ourselves enjoying a good meal, listening to our favorite music or being with friends and family that creates a sense of well-being that is most grounded.  Isn’t that what you would like to have in a product?  These feelings can’t be solely due to cerebral contentment, you have billions of other contributing opinions looking out for the same sense of well-being.  It’s time to listen more intently to those conversations.  One could have a hard time arguing which system truly dominates the conversation and thus our behavior and as a result our health.  Let not your strategy and ideation be limited to just one language.

Inspiration was gleaned from the following references:

The Neuro-Immune Axis in skin Sensation, Inflammation and Immunity, Anna M. Trier et. al., J Immunol, 2019 May 15: 202(10): 2829-2835.

Melanocytes: A Window into the Nervous System, Mina Yaar, et. al. Journal of Investigative Dermatology Volume 132, Issue 3, Part 2, March 2012, Pages 835-845

Inflammatory Resolution: New Opportunities for Drug Discovery, Derek W. Gilroy, et. al., Nature Reviews /Drug Discovery May 2004, 401-416.


Michael Anthonavage
VP of Operations & Technology

Eurofins CRL Cosmetic Testing, Inc.

Michael Anthonavage has 20+ years of experience in personal care product development and a career spanning background in skin biology. Michael has extensive knowledge in product development and product design.  He specializes in R&D to marketing translation, including claims validation both in-vitro and in-vivo. He is an engaging public speaker and product technology advocate with an ability to marry complex ideas and concepts to various consumer needs. Michael is currently the VP of Operations & Technology at Eurofins CRL Cosmetic Testing, INC.  Michael’s previous positions have involved R&D leadership positions at Johnson & Johnson Consumer Products, Presperse and Vantage Specialty Chemicals.  Michael is currently on the NYSCC Scientific Advisory Board and has won a variety of industry awards for his contributions in research and product development.   He has a number publications and patents to his name and continues to be an influential speaker in the personal care, bioinstrumentation and skin testing arena.

 

 

Sunscreen Monograph Proposed New Rules and its Impact on Formulations – Part III

by james.runkle@drummondst.com james.runkle@drummondst.com No Comments

Sunscreen Monograph Proposed New Rules and its Impact on Formulations-Part III

Introduction

Ever Since the FDA published its proposed rules in February of 2019 reclassifying 14 of the 16 sunscreens approved as Category I to Category II and III, the entire US sunscreen market has been upside down.  Most sunscreen manufacturers scrambled to formulate new products incorporating mineral sunscreens like Zinc Oxide and Titanium Dioxide since they were the only sunscreens left as Category I.

 

Mineral Sunscreens

Although most companies have mineral formulations already, these are mostly targeted to babies and young children.  Now the pressure is on to produce mineral sunscreens with high SPF suitable for all consumers and that can compete with organic formulations. This is a task that is not easily achieved, especially with the whitening effect associated with these formulations. Raw material suppliers have been also affected.  Polymers, SPF boosters, emulsifiers, and other key ingredients that provided a benefit in organic sunscreen formulations are no longer promoted. Instead, most raw material manufacturers have to promote ingredients that work mainly in mineral formulations.

 

Market Snapshot for Zinc-Based Formulations

A snapshot of the percent of zinc-based formulations launched globally from 2018 to 2020 (to date) is displayed in Figure I (below). The data shows that the US (34%) leads both Europe (10%) and Asia Pacific (27%) in the percent of new launches of zinc-based sunscreens.  This ratio is quite high and shows the effect of the recent scrutiny by the FDA on the safety of sunscreens in the US.  In general, the US market is in-line with the European market in terms of customer preference of organic-based versus inorganic-based sunscreen formulations.  Historically, inorganic sunscreens were more popular in Asia than the rest of the world due to their impact on skin tone.

 

Figure I. A comparison of the percent of global launches of zinc-based formulations from 2018 to 2020 (to date)

 

The progressions of the percent of new launches from 2018 to 2020 (to date) in the US, Europe and Asia Pacific are displayed in Figure II, III and IV (below).  In the US, the number of zinc-based formulations launched in 2020 increased by 7% from 2018.  This is a very significant increase considering that many launches in 2020 were postponed due to COVID-19.  In Europe the increase was more modest and kept only at 4%, whereas in Asia Pacific the increase was 8%.  It can be seen from the data that the global market was affected by the new direction seen in the US market.

 

Figure II. A comparison of the percent of launches of zinc-based formulations in North America from 2018 to 2020 (to date)

 

Figure III. A comparison of the percent of launches of zinc-based formulations in Europe from 2018 to 2020 (to date)

 

Figure IV A comparison of the percent of launches of zinc-based formulations in Asia Pacific from 2018 to 2020 (to date)

 

 

Possible European Actions

To add more complexity to the situation, the European Chemicals Agency, also known as ECHA, is considering classifying most zinc oxide and titanium dioxide sunscreens as microplastics.  Since most zinc oxide and titanium-dioxide particles are in the nano range and are typically coated with silicones or other hydrophobic materials, they fit the description of microplastics.  This argument is now being debated at the European Union.  Considering inorganic sunscreens as microplastics will warrant reformulation of hundreds of formulations worldwide and will have a huge global impact.  The impact will be very similar to the one created by the FDA in the US but this one goes in the opposite direction.  It will be interesting to see how companies will adapt to all the new regulations.  In one aspect, formulators with sunscreen background will be quite in demand and that is a positive outcome for formulation chemists especially during this global crisis of COVID-19.  This change will keep all our regulatory experts in demand as well, as someone must decipher what the FDA and ECHA are planning to do in the future.  Not to add more complexity, but I am sure China and Australia will come soon with their own guidelines.

 

Considerations for the Future

For now, the best bet is to be ready and have formulations that will be suitable for the various markets.  Global formulations might become a thing from the past.


About the Author

Dr. Hani Fares started his career in personal care studying the effect of solvents on sunscreen chemicals.  His interest in skin drug delivery especially from polymeric matrices grew during his graduate work at Rutgers, where he completed his Ph. D. in Pharmaceutics.

Dr. Fares worked at Block Drug and GlaxoSmithKline where he held positions in research and development in the areas of skincare and oral care.  After that, he joined L’Oreal where he held several positions of increasing responsibility leading to AVP of skincare.  He is currently the Senior Director of skincare and oral care at Ashland Specialty Ingredients.  Dr. Fares is the author of many publications, and patents and made many presentations in national and international meetings in the areas of suncare, skincare, and oral care.

 

An Overview on Hair Porosity

by james.runkle@drummondst.com james.runkle@drummondst.com No Comments

Introduction

Human hair is characterized by several descriptors, some of which influence how the hair behaves and responds to cosmetic products.  Common descriptors include texture, density and diameter.  Porosity is another relevant descriptor of hair that merits further attention.  It is advantageous for the industry to consider aspects of hair porosity given the rise of customization in hair care.  Further, the industry has become increasingly more interested in textured hair care.  Individuals with textured hair, hair that is naturally wavy, curly or coily, are more likely to have more porous hair than individuals with straight hair (1). Hair porosity resonates with textured hair consumers, especially considering that moisture and breakage are top concerns among this demographic (2).  The objective of this blog is to present a primer on hair porosity and its relevance to the cosmetic chemist and consumer alike.

Overview of Hair Porosity

Hair porosity describes the extent to which hair absorbs and retains water, products and treatments based on the integrity of the cuticle.  Porosity can be influenced by both genetics and hair grooming practices to varying degrees.  This blog will focus on the extremes of low and high porosity, but it should be noted that a mixture of low, normal and high porosity hair fibers can certainly exist in a head of hair.  Additionally, porosity can vary along the length of the hair fibers.

Normal or medium porosity hair absorbs and retains water reasonably well; hair can absorb 75% of the maximum amount possible within 4 minutes (3).  Normal hair is also receptive to chemical treatments such as bleaches, colorants and relaxers, and the results are generally predictable.

In low porosity hair, the cuticle layers are reinforced and lay flat leading to hair that is more resistant to water and chemical treatments.  From a consumer perspective, this is realized if  1.) the hair takes a significant amount of time to wet and dry, 2.) products build up easily on the surface rather than absorbing, 3.) protein treatments yield a stiff feel, and/or 4.) chemical treatments are less effective than expected.

In high porosity hair, the cuticle is compromised by configurational, mechanical and/or chemical stresses.  Textured hair represents a good example of how configuration can influence porosity.  Curls and coils are characterized by twists that lead to cuticle lifting at various points along the fiber, and this is more prevalent in the more elliptical hair fibers characteristic of individuals of African ancestry.  Mechanical stresses from daily grooming practices such as combing, brushing and hygral fatigue from repeated wetting (swelling) and drying (deswelling) can damage the cuticle over time, thereby exposing hydrophilic areas.  Chemical treatments such as oxidative colorants and ultraviolet radiation can affect hair porosity by oxidizing the protective surface lipids (3,4).

From a consumer perspective, high porosity presents as hair that absorbs water and dries quickly, maintains a dry feeling, experiences excessive frizz and breaks easily in some cases.  While high porosity hair quickly absorbs water, it also loses water quickly. The effects of chemical treatments are also accelerated and inconsistent in some cases, which can lead to damage.  For example, porous hair accepts hair colorants faster and the treatment can result in a cooler tone than that observed on less porous hair (5).

Consumer & Technical Methods for Hair Porosity

Select consumer and technical methods used to evaluate hair porosity are highlighted below.  Simple qualitative methods such as the Float Test and Spray Test have limitations but can potentially give a general idea under controlled conditions.

 – Float test: A qualitive assessment of porosity is made based on how quickly a clean hair fiber sinks when placed in room temperature water.  If the fiber more quickly sinks to the bottom, then it is porous.  If it floats over time, then it is likely low porosity.

– Spray test:  A qualitative assessment of porosity is made based on the behavior of water when sprayed on clean dry hair.  High porosity hair should adsorb the water more quickly than lower porosity hair, which would instead have visible beads of water and a longer dry time.

 – Dynamic Vapor Sorption (DVS) (6): The weight of hair is recorded as a function of increasing or decreasing humidity.

 – Gas Adsorption & Pore Size Analysis (7): Hair samples are subjected to nitrogen adsorption followed by mapping of the distribution and sizing of pores.

 – Fiber Swelling: The dimensions of a hair fiber are measured as a function of exposure to water. 

Hair Care Considerations by Porosity

The key concern for low porosity hair is hydrating the hair.  This can be facilitated with the use of a steamer, which simultaneously opens the cuticle with heat and infuses water vapor into the hair (8).  The steamer can be used to aid penetration during deep conditioning or to revitalize and moisturize hair as needed during styling.  The Q-Redew Handheld Steamer has become a quite popular tool.  Additionally, neat or formulated light-weight polar saturated oils can slowly absorb into the hair (1).  Rele et al demonstrated that coconut oil supports hair moisture retention and fortification by reducing water sorption and hygral fatigue (9).  Products that are less likely to penetrate the hair and result in buildup, i.e. some proteins, butters, etc. should be avoided in significant amounts, while those that contain humectants such as glycerin can be useful.

As the key concern for high porosity hair is moisture retention, consumers with this hair type benefit from sealing the hydrated hair with oils.  Consumers with textured hair frequently employ product layering to help retain moisture (in addition to styling).  This is referred to as the LOC or LCO method, in which the hair is hydrated with liquid or leave-in conditioner (L), followed by an oil (O) to seal the hair and then a creamy moisturizer/styler (C).  Polyunsaturated oils like avocado oil reportedly work best for high porosity hair.  While scientists have demonstrated that perceived hair moisturization does not correlate with actual hair moisture content (8,10), this method warrants attention given the satisfaction expressed by consumers.  It is plausible that the perceived improvement in “hair moisture” resulting from product layering techniques is due to the combined influence of at the least some of the following variables on the modification of the hair’s tactile properties: presence of product on the surface, oil penetration, and actual moisture content or localization.

In addition to sealing the hair with oils or product layering, high porosity hair can benefit from protein treatments.  Proteins can fill the voids of a compromised or lifted cuticle via film formation and penetration into the fiber. Further, products with significant levels of humectants should be avoided depending on the climate.

While there are marketed products that target hair porosity concerns, efficacy data are not available to the greater scientific community.  This opens the door of opportunity for the technical community to link technical capabilities such as the aforementioned methods with compelling data-backed product/ingredient stories.

Conclusion

As personalization in cosmetics/personal care continues to grow, the industry could benefit from further considering hair porosity.  Opportunity exists to further explore the distribution of hair porosity types and the link between porosity and CMC lipids, protein content, etc. beyond the current understanding.  Further research into this parameter could lead to ingredients, formulations, test methods, styling implements, and communications better tailored to address various hair porosities more effectively.  Linking consumer perception and practices with appropriate technical principles will be useful in meeting the needs of diverse hair types.

References

  1. Davis-Sivasothy, The Science of Black Hair (Saja Publishing Company, Texas, 2011), pp. 47-50, 78-91.
  2. Texture Media LLC. Texture Trends Consumer Study 2018.
  3. Dawber. Hair: its structure and response to cosmetic preparation, Clinics in Dermatology, 14, 105-113 (1996).
  4. Syed. Correlating porosity to tensile strength, Cosmetics & Toiletries, 117,11, 57-62 (2002).
  5. M. Frangie, L. Barnes, and Milady. Milady’s Standard Cosmetology Textbook, 1st ed. (Cengage Learning, Massachusetts, 2012), pp.630-631.
  6. Evans, “Adsorption Properties of Hair,” in Practical Modern Hair Science, T. Evans and R. Wickett. Eds. (Allured Business Media, Illinois, 2012), pp. 333-365.
  7. Z. Hessefort, B.T. Holland, and R.W. Cloud. True porosity measurement: a new way to study hair damage mechanisms, J. Cosmet. Sci., 59, 263–289 (2008).
  8. Schmid, H. Hair care appliance and method of using same. U.S. Patent 8,136, 263, filed August 21, 2008, and issued March 20, 2012.
  9. S. Reles and R.B. Mohle, Effect ofmineral oil, sunflower oil, and coconut oil on prevention of hair damage, J. Cosmet. Sci., 54, 175-192 (2003).
  10. Davis. Moisture vs. Moisturization: Understanding the Consumer Benefit, P&G Beauty Care Presentation, TRI 5th International Conference on Applied Hair Science (2014).

 


 

Dr. Amber Evans is a cosmetic industry professional with over a decade of experience and expertise in the science of hair and skin care.  In her current role as Senior Manager of Product Development at Moroccanoil, she is responsible for driving the development of high-quality innovative hair & body care products for the successful global brand.  She previously worked at as a development scientist at BASF Corporation, where her contributions spanned multiple market segments, including hair, body and oral care, and the technical areas of innovation and claims testing over eight years.

Dr. Evans earned a Ph.D. in Pharmaceutical Sciences (Cosmetic Science focus) from University of Cincinnati and a B.S. in Chemistry from North Carolina Agricultural & Technical State University.  She has conducted extensive research into the influence of water hardness on hair and has contributed to initiatives including upstream research for hair colorants, hair conditioner formulation and clinical testing for skin/shave care applications at The Procter & Gamble Company.  She has also authored hair care research publications, contributed content to NaturallyCurly.com, the leading resource for textured hair care, and featured on multiple platforms that support aspiring scientists and early career professionals.  As a mentor, active member of the Society of Cosmetic Chemists (SCC) and of the NYSCC Scientific Committee, peer reviewer for the Journal of Cosmetic Science and member of the Advisory Board for the University of Cincinnati Cosmetic Science Program, Dr. Evans is dedicated to influencing the progression of the cosmetic field.

 

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