“Aged? But he does not appear aged, just look, his hair has remained young!” Marcel Proust, In Search of Lost Time (1913–27) The appearance of hair plays an important role in peoples’ overall physical appe- ance and self-perception. With today’s increasing life-expectation, the desire to look youthful plays a bigger role than ever. The hair care industry has become aware of this, and capable to deliver active products that are directed toward meeting this c- sumer demand. The discovery of pharmacological targets and the development of safe and effective drugs such as minoxidil and fnasteride also indicate strategies of the drug industry for maintenance of healthy and beautiful hair in the young and old. The study of hair aging focuses on two main streams of interest: On the one hand, the esthetic problem of aging hair and its management, in other words everything that happens outside the skin; on the other hand, the biological problem of aging hair, in terms of microscopic, biochemical, and molecular changes, in other words the “secret life” of the hair follicle in the depth of the skin. Hair aging comprises hair shaft aging, and aging of the hair follicle. The former involves weathering and photoaging of the hair shaft, while the latter manifests as decrease of melanocyte function (graying) and decrease in hair production (alopecia).
