I originally wanted to write this column in the Spring, when stronger UV rays would make their appearance in the Northern Hemisphre. Since we are having unseasonably and unpredictably warm weather and sunnier days in the Mid-Atlantic region, I decided to write about UV effects on hair a bit earlier. My interest in this topic was piqued when I first heard of chelating agents affecting hair health at a World Hair Congress. The hair care industry has been tackling the effects of pollution and UV damage on our hair such as free radicals. What about the stuff we use every day at home—like tap water?

During my freshman year at Howard University, the resident assistant used bottled water to wash her hair as the tap water in DC left her hair dry and brittle, unlike the water in her home town. What was thought to be luxurious in 1992—yes, I am over 30—has been proven in recent years.

It is well known that prolonged exposure to sunlight results in hair damage, ultimately leading to tensile strength loss, brittleness, and color changes.¹ It also leads to loss of luster, split ends and increased surface friction.¹ The process occurs via a free radical chain reaction that is initiated by the high-energy UV wavelengths present in sunlight and propagated in the presence of atmospheric oxygen, resulting in oxidation of protein and lipid components.¹

Trace metals, in particular copper ions absorbed into the hair fibers from tap water, increase the rate of free radical oxidation.¹ In pigmented hair, melanin granules partially protect the protein and lipid components from oxidation, although the hair becomes lighter as melanin is oxidized.¹


UV Exposure & Hair Care


So, how does exposure to ultraviolet rays actually affect hair? It is well known that pigmented hair exposed to sunlight becomes lighter due to photobleaching of melanin granules in the fiber cortex.¹ Visible light is mainly responsible for photobleaching.¹ However, natural white and gray hair contain little melanin pigment and become yellower when exposed to sunlight.¹

Transepidermal ultraviolet rays (UVR) exert skin cytotoxicity and epidermal damage. In an ex-vivo study high and/or low UVA+UVB doses also induced oxidative DNA damage and cytotoxicity in human hair follicles (HFs).¹ In addition, it decreased proliferation and promoted apoptosis of HF outer root sheath (ORS) and hair matrix (HM) keratinocytes, stimulated catagen development, differentially regulated the expression of HF growth factors, and induced perifollicular mast cell degranulation.¹ The effects of UVR are damaging to the hair and detrimental to hair growth.

ROS and Damage

How do hair color and copper ions cause reactive oxygen species and hair damage? The damage caused by oxidative hair colorants and UV exposure has been well documented in the literature.² Hair coloring is very popular with more than 50% of women in some countries regularly using hair colorants, typically once every 6–8 weeks.³ Hair colorants containing hydrogen peroxide as the oxidant are the most popular, making up approximately 80% of the market for these products.² The hydrogen peroxide has a dual function of oxidizing and decolorizing melanin in hair which lightens the underlying hair color and oxidizing the dye precursors to form synthetic color.³ The damage species formed during hair coloring with these products includes the perhydroxyl anion (HOO-) and reactive oxygen species (ROS) such as hydroxyl radicals (HO). UV exposure also involves oxidative pathways and formation of ROS such as hydroxyl radicals, singlet oxygen and alkoxyl radicals.³ The role of metals such as copper and iron that can undergo one-electron chemistry is well known for catalytically accelerating oxidative processes and producing redox metal-induced radical species.³

In one study, to determine whether copper is present in consumer hair, a harvest of hair samples from more than 400 women was undertaken from nine countries around the world.³ Small hair samples were taken as well as a questionnaire to gather information from the women on their perception of hair health. The hair harvest data demonstrated that copper is present in hair for all countries tested, and as expected, there is a range of levels in hair, and it is well known that even very low levels of copper and other metals can accelerate free radical generation due to their catalytic nature.³ This is supported by the fact that the study demonstrated a correlation between self-perception of hair damage and the copper level in hair.³

Formation of highly reactive radical species as a likely cause of hair damage was confirmed by measuring protein degradation of the keratin proteins and keratin-associated proteins (KAPS) in hair.³ Protein degradation was assessed by performing a protein loss experiment where the hair was first exposed to the oxidative insult—either an oxidative colorant or UV exposure. The hair was then washed in water for an hour to elute any degraded proteins. The amount of protein eluted was measured. The influence of copper on protein degradation was measured by including a sample with copper levels in the range expected from the hair harvest. Results from these studies demonstrated that copper in hair does lead to more protein degradation in the presence of both hair colorant and UV exposure.³

So, What’s the Solution?

I do not have enough column space to delve into that this month, but here is a teaser: UV absorbers, antioxidants, radical scavengers and metal chelators are widely used in synthetic polymers to provide protection from the same free radical oxidation process, and a similar approach using non-toxic additives is attractive for new hair care products. 


References

1. Millington and Marsh. Damage to Hair and the Effects of Anti-Oxidants and Metal Chelators. International Journal of Cosmetic Science. Accepted.
2. Gherardini et al. Transepidermal UV radiation of scalp skin ex vivo induces hair follicle damage that is alleviated by the topical treatment with caffeine. Int J Cosmet Sci. 2019 Apr; 41(2): 164–182.
3. Marsh, J.M. et al. Preserving fibre health: reducing oxidative stress throughout the life of the hair fibre. International Journal of Cosmetic Science, 2015, 37 (Suppl. 2), 16–24

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Sharleen St. Surin-Lord
Dermatologist
Email: derm@visagederm
Website: www.visagederm.com

Dr. Sharleen St. Surin-Lord is a board-certified dermatologist who has been practicing for more than 13 years. She is in private practice at Visage Dermatology, Largo MD. She also practices at the University of Maryland Capital Regional Health System in Maryland and she is an assistant professor of dermatology at Howard University College of Medicine. “Dr. Sharleen” is a member of the American Hair Research Society and you can follow her on Twitter, Instagram, and Facebook as DermHairDoc.