Photoageing of hair fiber and photoprotection.

Examination by transmission electron microscopy of hair exposed to sunlight has revealed important damage. Findings indicate an alteration of various cell components. Damage occurs in the cuticle and leads to its loss. Separation of macrofibrils and destruction of melanin pigments result in cortex damage. Some of the chemical and physical changes which occur in hair exposed to sunlight were studied: formation of carbonyl groups, cystine destruction, modification of the proteins obtained by reduction of the disulfide bonds, losses in mechanical strength and discoloration are discussed. Effects of UV and visible radiations were studied. All of them cause modification in hair properties. Experiments with artificial light sources were carried out to reproduce these alterations. The role of water during exposure was studied. In particular, discoloration of brown hair is largely affected by it. We showed that Xenon lamps were useful to follow the photooxidation of hair and simulate natural alterations. The properties of some protective materials were examined.