F24 HAIR SHAFT AGING
Lee WS, Oh TH, Jeon SY
Department of Dermatology and Institute of Hair and Cosmetic Medicine, Yonsei University Wonju College of Medicine, Korea

Hair is constantly subjected to repeated environmental assaults, commonly termed "weathering", which aggravated from sunlight and exogenous chemical damages such as hair dye or permanent wave. These factors cause extrinsic hair shaft aging in addition to natural intrinsic hair shaft aging. On the hair surface, cells are covered with a thin lipid layer covalently bonded to hair proteins. The authors conducted this study to examine the morphological and chemical changes of the aging hair shaft. The hair shafts were treated with various kinds of extrinsic assaults including cosmetic hair dyeing, permanent waving, natural sunlight and artificial ultraviolet damage. Electron microscopy was performed to observe the ultrastructure of hair shaft and integral hair lipid layer at different levels from the very base of the hair follicle till the end of hair tip for those treated hair shaft. In addition, we measured the chemical composition of integral hair lipid by HPLC. From the above experimental procedure, it was discovered that the integral hair lipid were mainly distributed within the intercellular layers of cuticle cells and partly affected by extrinsic hair damages. Also the general architecture of the hair shaft was partly changed by various extrinsic damages, which aggravated the process of hair shaft aging.