Journal of Cosmetic Dermatology, 13, 1--2

Hair, sun, regulation, and beauty

Zoe Diana Draelos, MD

The recent sunscreen guidance issued by the US FDA

prohibited the use of SPF ratings on hair-care products,

even though these products may contain photoprotec-

tive ingredients listed on the sunscreen monograph.

The US FDA has also questioned the adequacy of

photoprotection provided by spray on sunscreens.

These concerns are understandable based on the dis-

continuous film created by spray on products. It is esti-

mated in clinical testing that the SPF on the packaging

can only be achieved if the spray sunscreen is applied

following by rubbing three consecutive times. While

this is possible on skin, it is not possible on hair. Spray

sunscreens for the hair cannot possibly evenly coat

every square inch of the hair shaft. It also doubtful

how much sun protection is provided by shampoos

and rinse away instant conditioners that contain sun-

screen. The short contact time followed by abundant

water rinsing may remove any photoprotection. This

then begs the question as to whether nonliving hair

shafts really need sun protection at all. The answer is

most emphatically “yes,” and I will proceed to explain

this important cosmetic need.

As hair is nonliving, it cannot be sunburned or

undergo photocarcinogenesis; however, UV and visible

radiation are very damaging to the cosmetic value of

the hair. Much of the current understanding of hair

photodamage comes from textile research on wool.

Natural fibers, such as wool, cotton, silk, and rayon,

discolor when exposed to sunlight. White fabrics tend

to take on a light brown/yellow color, a process known

as photoyellowing. In natural human hair, there are

two pigments, eumelanin and pheomelanin, account-

ing for the brown and red hues seen in hair,

respectively. There is another melanin, known as oxy-

melanin, found in unprocessed human hair that has

been exposed to sunlight. Oxymelanin is an oxidative

photodegradation product.1

Lighter-colored hair, such as blonde hair, is more

susceptible to hair photodamage than deeply pig-

mented hair, such as brown hair. Black hair begins to

lighten in color after 300 h of exposure to simulated

sunlight, while blonde hair begins to yellow after

300 h of exposure to simulated sunlight and begins to

lighten when exposed to 300–1200 h of simulated

sunlight exposure. The hair color lightening or bleach-

ing is primarily due to the effects of visible light. How-

ever, not only does the hair change color, but it also

experiences a 200–300% increase in friction, indicat-

ing damage to the proteins in the cuticle.

The hair protein that is mainly damaged by sunlight

is cystine, which is oxidized to cysteic acid. It is the

sulfur-containing amino acids that are most sensitive

to oxidative damage, and of course, it is the sulfur-con-

taining amino acids that give the hair its structural

strength. Other amino acids, such as tryptophan and

tyrosine, are also degraded by light. After 150 h of sun

exposure, blonde hair shows a 25–30% decrease in

tryptophan, 25% decrease in cystine, and 80%

decrease in tyrosine. As oxidation occurs, there is a

compensatory 80% increase in cysteic acid. These

same changes are also seen in black hair, but at least

300 h of sun exposure was required to produce the

same oxidative damage.2

Sunlight also decreases the tensile strength of the

hair fiber. This means that when the hair is combed

and stretched, it is more likely to break. This effect is

magnified with age as the diameter of the hair shaft

decreases in both men and women. The diameter of

female hair shaft increases up to age 35 and then

decreased gradually after age 40 with further decreases

after menopause. In men, the diameter of the hair

shaft decreases after puberty.

The natural photoprotection in hair is melanin, which

also provides endogenous photoprotection in the skin.

Melanin is broken down by visible and UV radiation in

the hair shaft giving rise to a phenomenon known as

photobleaching. This phenomenon is especially pro-

nounced in blonde hair, which lightens dramatically in

the summer, but also results in permanent changes in

the hair shaft internal amino acids and external lipids.

Unpigmented hair, such as gray and white hair, is

more susceptible to UV damage than pigmented hair.3

Also, the rate of cystine disulfide bond breakage is

greater for unpigmented than pigmented hair. This

means that one of the best sources of photoprotection

is hair dye.

© 2014 Wiley Periodicals, Inc. 1

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White unpigmented hair looses more mechanical

strength after 4 days of UV radiation than semiper-

manently dyed brown hair. This same effect is also

present with permanent hair dyes. The permanent

hair dye acts as a passive photofilter reducing the

hair fiber protein damage by attenuating the incident

light. The dye molecule absorbs the light energy,

which promotes it to a more excited stated, followed

by a return to ground state via radiative and nonra-

diative pathways. As might be expected, the darker

the hair color the more photoprotection imparted by

the dye.

SPF rated sunscreens to promote hair beauty and

health probably will not be forthcoming in light of the

new sunscreen guidance. Indeed, consumers might

misinterpret sunscreen-containing hair products and

mistakenly think that if the shampoo runs over the

body, adequate sunscreen might be left behind. Yet,

there is a need within current regulation to address

the fact that sun exposure is detrimental to hair

beauty. Consumers seem much more pre-occupied with

having a “good hair day” than wearing sunscreen on

their face and bodies to insure a “good skin day”.

Perhaps cross-education from sunscreen-containing

hair-care products might spill over into proper skin

sunscreen application, especially in impressionable ado-

lescents. It is also worthwhile to give consumers an

idea of how much photoprotection they are getting

from hair-care products to maintain hair beauty. With

new sunscreen technology, it may be time to create a

separate hair sun protection scale to make consumers

aware of how to more effectively beautify their hair.

Who knows, it might be enough to encourage a

renewed interest in skin photoprotection!

References

1 Hoting E, Zimmerman M. Sunlight-induced modifications

in bleached, permed, or dyed human hair. J Soc Cosmet

Chem 1997; 48: 79–91.2 Gonzenbach H, Johncock W, De Polo KF et al. UV damage

on human hair. Cosmet Toilet 1998; 113: 43–9.3 Tolgyesi E. Weathering of hair. Cosmet Toilet 1983; 98:

29–33.

2 © 2014 Wiley Periodicals, Inc.

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