Development Research ,Hair Care Products Research, Kao Corporation, Japan
Dr. Itou has been involved in fundamental hair research and hair care product development at Kao Corporation since 1991. He has his expertise in structural and physical property analyses of hair shaft and is particularly engaged in the structural analysis of curly hairs and the change in hair shaft by aging.
Various changes appear in hair by aging and graying is the most remarkable one. Changes in melanocytes have been well studied as the cause, however, little is known about the change of melanosomes which have a role of carrying melanin pigments into hair shafts. Using pigmented hairs of Japanese females from their age of 4 to 75, I isolated melanosomes and observed them. As a result, I found a significant change in the morphology of hair melanosomes with age. They were ellipsoidal on the whole and there was no age dependence in the major axis, while the minor axis significantly increased and its frequency distribution broadened with age. The anticipated volume of the melanosome of the oldest person hairs was about twice larger than that of child hairs. By being compared the hair bundles in a wide range of age, it was found that the color of pigmented hairs changes from brown to black with age. There was no age dependence in the thickness of hair fibers. On the other hand, color parameters (L*a*b*) of these hair bundle showed the dependency on age and also they correlated with the shape parameters of melanosomes. This suggests that the enlargement of melanosome seems to be a cause of the age-related color change of pigmented hairs from brown to black. In this presentation, other possible causes for the hair color change will also be discussed.