What causes telogen effluvium?

Hair normally cycles through growing, resting, and shedding phases. Telogen effluvium happens when a larger group than usual enters the resting phase after a trigger. Shedding may become noticeable during washing, brushing, or on clothing. Common triggers include a significant infection or fever, surgery, marked emotional strain, restrictive eating, low iron or other nutritional deficiency, thyroid disturbance, and changes after pregnancy. The trigger may occur before the shedding becomes obvious, so the timing is not always easy to connect.

This pattern usually affects the scalp diffusely rather than creating one sharply outlined bald patch. A clinician can distinguish it from other causes of hair loss by examining the scalp and discussing medicines, diet, recent illness, and the hair-cycle history.

Think back over the months before shedding began and write down illnesses, major stress, dietary changes, new medicines, pregnancy-related changes, and menstrual or thyroid concerns. Eat regularly with adequate protein and avoid tight hairstyles, harsh chemical processing, and vigorous brushing while the scalp is shedding. Do not start high-dose supplements without advice, because excess nutrients can also disturb hair growth. A clinician may check for an underlying nutritional or hormonal problem and discuss whether the pattern fits telogen effluvium.

Arrange a dermatology assessment if shedding is heavy, continues, returns repeatedly, or is accompanied by scalp pain, scaling, inflammation, broken hairs, or a smooth patch. Seek prompt medical advice when hair loss occurs with marked fatigue, unexplained weight change, persistent fever, or other new body symptoms. Earlier assessment is also sensible when the change is distressing or you cannot identify a possible trigger.

Ask whether the distribution and timing fit telogen effluvium, which trigger is most plausible, whether blood tests could clarify iron or thyroid status, and how to protect the scalp while new growth develops.