The resting phase of the hair follicle — the growth phase is over, the follicle is dormant, and the hair is preparing to shed.Typically lasts 3–5 months. At any given time, roughly 10–15% of scalp follicles are in telogen. Telogen effluvium is diffuse hair shedding triggered by a stressor (physical illness, surgery, severe psychological stress, rapid weight loss, childbirth) that prematurely drives a large cohort of follicles into telogen simultaneously. The shedding appears 2–3 months after the triggering event — the lag time is the remaining telogen phase before those follicles shed. Most telogen effluvium resolves spontaneously once the stressor is removed.