[Biology of the human hair follicle. New knowledge and the clinical significance].

Recent advances in molecular and cell biology have led to increased understanding of hair formation, hair growth, and cycling. Follicular pigmentation processes, neuroendocrine regulation, immune status, and follicular stem cell research in addition to the development of techniques to specifically target the hair follicle will help advance new therapeutic approaches in the management of hair diseases. In this article we review general aspects of hair biology, recent developments regarding hormonal regulation and pigmentation, the possible roles of the follicular immune system, advances in follicular stem cell research, and follicular penetration in view of their clinical relevance.