HAIR PHOTODAMAGE - MEASUREMENT AND PREVENTION

A spectroscopic technique, based on the intrinsic fluorescence of hair keratin, has been used to monitor the concentration of tryptophan in hair. Experiments performed by using either artificial light or natura l sunlight have shown that tryptophan is photolabile, and undergoes de composition on exposure to UV light in the 295- to 315-nm range. Hair weathering was found to produce significant loss of tryptophan, togeth er with other chemical changes in the keratin structure such as the ox idation of disulfide bonds to cysteic acid. Thus it is shown that tryp tophan in hair can serve as a sensitive marker of hair photodamage, It is also demonstrated that hair care formulations containing sunscreen s can reduce the extent of photodamage. Furthermore, the tryptophan de composition rate was found to be substantially slower in mineral oil-t reated hair, compared to water-treated control. These data suggest tha t hair care formulations containing non-chromophoric material may also reduce photodamage.