Anagen, catagen and telogen are terms that determine the periods of the cycle of the growing hair. Anagen is the phase when hair looks well nourished and grows continuosly. Following this phase, there's a brief phase called catagen, that is a degradation period, throughout which the hair follicle is cut of from the blood supply. During this degradation phase, the hair follicle begins to shrink as well as the hair shaft is pushed upwards.
