Telogen Effluvium

Telogen effluvium is a form of diffuse hair shedding. More hairs than usual move into the resting phase of the hair cycle, often following a physical or emotional stressor. Shedding is typically noticed across the scalp rather than as a single sharply defined bald patch.

What can trigger it?

Recognised triggers include acute illness with fever, major surgery, childbirth, marked weight loss, restrictive diets, severe emotional stress and some medicines. Iron deficiency and thyroid disease may contribute in some people. Because the hair cycle changes slowly, shedding may begin several months after the triggering event.

How it is assessed

A clinician will ask about the timing and pattern of hair loss, recent illness, pregnancy, weight change, diet, medicines and other symptoms. Examination helps distinguish diffuse shedding from pattern hair loss, alopecia areata, scarring alopecia and scalp disease.

Blood tests are selected according to the history. They may include a full blood count, ferritin and thyroid testing, but there is no single blood test that proves telogen effluvium. Results should be interpreted clinically rather than used as stand-alone explanations for hair loss.

Read about ferritin and iron stores.

What usually happens?

Acute telogen effluvium often improves after the trigger has resolved, although visible recovery can take months because hair grows slowly. Persistent or recurrent shedding warrants reassessment for an ongoing trigger or another diagnosis. Supplements are not automatically beneficial and should not be taken in high doses unless a deficiency has been identified or a clinician recommends them.

When to seek medical advice

Arrange an assessment if shedding is severe, lasts longer than six months, causes visible thinning, follows a new medicine, or occurs with symptoms such as weight change, menstrual disturbance or marked fatigue. Seek prompt dermatology advice for scalp pain, inflammation, scaling, scarring, rapidly expanding bald patches, or loss of eyebrows or eyelashes.

Limitations

Remote information and blood testing cannot diagnose every cause of hair loss. Diagnosis may require examination, dermoscopy or occasionally additional investigation. Do not stop prescribed medicines because of suspected hair shedding without speaking to the prescriber.

Sources

• British Association of Dermatologists: Telogen effluvium patient information

Explore available blood tests. A test can investigate selected contributors but does not replace a hair and scalp assessment.