GPAtlas🧭 When to suspect
Telogen effluvium is the commonest cause of diffuse, non-scarring hair shedding.
It follows a “shock to the system” that pushes an abnormally large proportion of follicles out of the growth (anagen) phase and into the resting (telogen) phase, so that they shed together a few months later.
• In a normal scalp about 85% of follicles are in anagen and 15% in telogen.
• It is normal to lose up to ~100 hairs a day.
• A significant trigger can precipitate up to 70% of follicles into telogen at once.
The hallmark is a clear precipitating event 2–6 months earlier, followed by sudden, generalised shedding – hair “coming out in handfuls” in the shower, on the pillow or in the brush.
• The scalp looks normal (no redness, scaling, pustules or scarring) and there are no bald patches.
• Because the follicles are preserved, the condition is self-limiting: density usually returns to normal 6–9 months after the trigger resolves, although full cosmetic recovery can take up to a year.
Three steps:
• Confirm the diagnosis from the story and a normal scalp
• Exclude the mimics (scarring alopecia, pattern hair loss, alopecia areata)
• Identify reversible causes – above all iron deficiency and thyroid disease
| Physical or physiological triggers |
|---|
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• Childbirth (post-partum or telogen gravidarum), typically 2–4 months after delivery |
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• Severe febrile illness or infection (e.g. COVID-19, sepsis) |
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• Major surgery or general anaesthesia |
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• Significant trauma or accident |
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• Acute severe psychological stress or bereavement |
| Hormonal, nutritional & drug triggers |
|---|
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• Iron deficiency – with or without anaemia (the commonest reversible cause) |
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• Thyroid dysfunction – hypo- or hyperthyroidism |
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• Crash dieting, rapid weight loss, low protein or restrictive eating, including rapid loss on GLP-1 weight-management drugs (Wegovy, Mounjaro) |
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• Zinc or vitamin D deficiency |
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• Drugs – retinoids, beta-blockers, anticoagulants, some antidepressants, ACE inhibitors; or stopping the combined oral contraceptive pill |
Source: British Association of Dermatologists · DermNet
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