telogenphase

Telogen phase, or telogen phase of the hair cycle, is the resting stage during which hair follicles are not actively producing new hair. It follows the catagen transition and ends when a new anagen phase begins. In humans, about 10 to 15 percent of scalp hairs are in telogen at any given time, though this proportion can rise in certain conditions.

During telogen, the hair follicle is in a quiescent state and the hair shaft remains in place as a club hair. The lower part of the follicle is inactive, and the shedding of these hairs can occur naturally after a few months or more, when a new anagen phase is initiated and the old telogen hair is pushed out by the growing new hair.

Telogen duration varies by body site and individual factors. Scalp telogen may last several months, whereas body hair generally has shorter telogen periods. The balance of growth (anagen), regression (catagen), and resting (telogen) phases is influenced by genetics, hormones, nutrition, and overall health.

Clinically, an abnormal increase in telogen hairs can lead to telogen effluvium, a diffuse shedding condition often triggered by illness, childbirth, stress, fever, medications, or nutritional deficiencies. Telogen effluvium typically presents a few months after a triggering event and is usually reversible with treatment of the underlying cause and time for hairs to re-enter anagen. Diagnosis relies on history, examination, and sometimes hair pull testing or trichoscopy.