What causes anagen effluvium?

Medicines that interfere with rapidly dividing cells can weaken the growing hair shaft, causing it to break or shed. The extent varies with the medicine, dose, schedule and individual response, and not every treatment produces the same pattern.

During the anagen phase, follicle cells divide quickly to build the hair fibre. Treatments or toxic exposures that damage these cells can narrow or fracture the fibre before the follicle naturally enters its resting phase. This explains why shedding may feel sudden and can involve scalp hair as well as eyebrows, eyelashes or body hair.

Anagen effluvium differs from gradual patterned thinning and from shedding that follows a delayed shift into the resting phase. A clinician uses timing, distribution, medicine history and scalp findings to distinguish these patterns.

Tell the team prescribing your treatment about hair loss, but do not stop or alter essential medicine on your own. Ask what hair changes are expected with the specific regimen and whether scalp-cooling is appropriate and available for that treatment. Its suitability depends on the diagnosis and therapy.

Handle fragile hair gently: use a mild shampoo, pat rather than rub, limit heat and chemical processing, and avoid tight styles. Protect exposed scalp from strong sun and choose a soft head covering if the skin feels sensitive. Discuss topical minoxidil before use because it does not prevent every cause of anagen injury and may irritate the scalp.

Contact your treating team if shedding is unexpected for your medicines, begins without a clear exposure, or comes with scalp pain, marked redness, scaling, sores or discharge. Prompt advice is also appropriate if hair loss is accompanied by a new rash, facial swelling, breathing difficulty or other signs of a medicine reaction.

Ask whether the timing and pattern match anagen effluvium, which treatment is the likely trigger, whether the scalp needs examination and what regrowth may look like after the exposure ends. You can also discuss scalp comfort, camouflage options and whether any proposed hair-growth product could interact with your care.