Hair, sun, regulation, and beauty

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  • 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 3001200 h of simulatedsunlight 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 200300% 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 2530% decrease intryptophan, 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

    Editorial Echoes

  • 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: 7991.2 Gonzenbach H, Johncock W, De Polo KF et al. UV damage

    on human hair. Cosmet Toilet 1998; 113: 439.3 Tolgyesi E. Weathering of hair. Cosmet Toilet 1983; 98:

    2933.

    2 2014 Wiley Periodicals, Inc.

    Editorial Echoes