Telogen effluvium (Telogen effluvium (TE))

Telogen effluvium (TE) is the most common cause of sudden diffuse hair shedding. A physiological stressor pushes a large fraction of growing follicles into the resting (telogen) phase prematurely; they all shed together 2 to 4 months later.

Common triggers: significant illness or surgery, childbirth, severe psychological stress, crash dieting, iron deficiency, thyroid dysfunction, starting or stopping certain medications.

The 2 to 4 month delay between trigger and visible shed is the source of most diagnostic confusion. By the time shedding starts, the trigger is often already in the past, which is why people miss the connection.

Acute TE typically resolves in 6 to 9 months once the trigger is gone. Hair density usually returns to baseline; the follicles are not damaged. Chronic TE is a less common, longer-running variant without an identifiable trigger that primarily affects women.

No pharmaceutical reliably shortens acute TE. Treatment is identifying and addressing the trigger, correcting any deficiencies (ferritin, vitamin D, thyroid), and patience.