For decades, the hair cycle and its control have been an object of debate. Clearly, the hair follicle is the only organ in mammals, which “cyclically” degenerates and regenerates from stem cells, and the understanding of such a unique behavior would certainly give clues to tissue homeostasis and regeneration. A number of factors have been identified which can modulate this process, but its choreography remains elusive. For years, the hunt for the conductor has been on, but nobody ever caught him. Intuitively, the process being considered as cyclic, an automaton controlling this cycle should be looked for, by analogy with a clock. A famous paper evidenced the failure in this task (1) and the question remains: why is-it so difficult to identify and characterize this oscillator? My answer is simple: it simply does not exist. We have revealed that each follicle has an autonomous stochastic behavior, the probability of duration of each phase fitting with a lognormal equation (2). From this analysis, one can conclude that instead of a cyclical behavior with an intrinsic automaton, the hair follicle has a chaotic behavior. This new concept postulates the existence of a bi-stable equilibrium which controls hair follicle behavior, which under a stochastic way jumps from the dormant to the active branch of the equilibrium and vice-versa.

1: Paus R., Foitzik K. Differentiation 2004, 72:489-511.
2: Halloy J, Bernard B.A., Loussouarn G., Goldbeter A. Proc.Natl.Acad.Sci. 97 :8328-8333 (2000)