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, and 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. Crucially, 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.
The clinical task in primary care is threefold: confirm the diagnosis from the story and a normal scalp, exclude the mimics (scarring alopecia, pattern hair loss, alopecia areata), and identify reversible causes – above all iron deficiency and thyroid disease.
| Physical / physiological triggers | Hormonal, nutritional & drug triggers |
|---|---|
|
• Childbirth (post-partum / telogen gravidarum), typically 2–4 months after delivery |
• Iron deficiency – with or without anaemia (the commonest reversible cause) |
|
• Severe febrile illness or infection (e.g. COVID-19, sepsis) |
• Thyroid dysfunction – hypo- or hyperthyroidism |
|
• Major surgery or general anaesthesia |
• Crash dieting, rapid weight loss, low protein or restrictive eating |
|
• Significant trauma or accident |
• Zinc or vitamin D deficiency |
|
• Acute severe psychological stress or bereavement |
• 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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