Key facts
- The cycle
- About 85 to 90 per cent of follicles are growing (anagen) and 10 to 15 per cent resting (telogen) at any time
- The disruption
- A physiological shock pushes many follicles into telogen at once
- The delay
- Shedding begins about two to three months after the trigger, because telogen lasts roughly that long
- Classic triggers
- Childbirth, high fever or severe illness, surgery, crash diets, major stress, some medicines
- Diagnosed by
- History and timeline, examination of the scalp and shed hairs, and blood tests where indicated
What is telogen effluvium?
Telogen effluvium is the hair cycle stumbling in unison. Normally follicles cycle independently, so roughly 85 to 90 per cent are growing while 10 to 15 per cent rest, and the daily shed is modest and unnoticed. A physiological shock, a febrile illness such as dengue or COVID, a delivery, an operation, a crash diet or a period of severe stress, pushes thousands of follicles into the resting phase together. Telogen lasts around three months, so the hairs are released together months later.
That delay is the clue everyone misses. The handfuls in the shower appear when life has returned to normal, and the connection to the trigger goes unmade. The shed hairs themselves carry the signature: a small white bulb at the root, the mark of a telogen hair rather than a broken one. Shedding is diffuse across the scalp rather than patterned, and the scalp itself looks normal, without scaling, redness or scarring.
How is it assessed and managed?
The diagnosis is made by history and timeline: mapping the trigger two to four months back, examining the scalp and the pattern of thinning, and looking at the shed hairs. Blood tests for ferritin, thyroid function and nutritional markers screen for factors that perpetuate shedding, and in women this blood work comes before any treatment is recommended. The physician's other job is to check whether the episode has unmasked underlying pattern hair loss, which is common and changes the plan.
Classic acute telogen effluvium resolves as the cycle desynchronises and density rebuilds over months, typically within about six months of the trigger resolving. Management is mostly the right diagnosis, correction of anything correctable and time. Aggressive scalp treatments cannot shorten telogen, supplements correct nothing unless a deficiency has been measured, and counting shed hairs daily amplifies anxiety, which at its severest is itself a described trigger. Dr Sin Yong sets this out on his sudden hair shedding page.
“Telogen effluvium sheds in the calm after the storm — the delay is why nobody connects it.”
Dr Sin YongOn why the trigger is so often missed
What is it often confused with?
Androgenetic alopecia, or pattern hair loss, is the main confusion, and the two often coexist. Pattern loss is gradual and mapped to the parting, crown or temples, driven by follicle sensitivity to androgens; telogen effluvium is abrupt, diffuse and trigger-linked. The distinction matters because a shedding episode can be the moment a woman first notices thinning that was already there, and waiting without examination can waste the window for the condition underneath.
Alopecia areata produces sudden round bald patches rather than diffuse shedding, and traction alopecia follows the line of tension from tight styling. Anagen effluvium, seen with chemotherapy, sheds growing hairs within days to weeks rather than resting hairs months later. Scarring alopecias leave a shiny scalp without follicle openings. Each of these looks different on examination, which is why a diagnosis is not made from a photograph of a hairbrush.
When is watching and waiting not the answer?
Shedding that persists beyond about six months, or that recurs in waves, points to chronic telogen effluvium or an ongoing driver such as iron deficiency, thyroid disease, a medicine or a dietary problem, and needs investigation rather than reassurance. Patches, scalp itch, pain, scaling or redness are not features of telogen effluvium and should be assessed promptly, because they suggest a different diagnosis.
Where pattern hair loss has been unmasked, the plan changes from waiting to treating that condition, and the options are set out on the female hair thinning and hair restoration pages. Where a medicine is the suspected trigger, it is reviewed with the prescribing doctor rather than stopped unilaterally. Telogen effluvium is a diagnosis made by a physician, and buying six treatments for a condition that resolves on its own is the outcome the assessment exists to prevent.
