Patchy hair loss: causes, red flags and when to get it checked

Patches of hair loss occur when part of the scalp is targeted by the immune system, infected, scarred, pulled or affected by skin disease. The skin surface of the patch, the presence of scale, redness and broken hairs, and the pattern of loss guide the diagnosis.

• Alopecia areata: sudden, smooth, round patches, sometimes in the beard or eyebrows, associated with autoimmune conditions and thyroid disease.

• Traction alopecia from tight hairstyles, braids, extensions or hair ties, with thinning at the hairline and temples.

• Tinea capitis (scalp ringworm): scaly patches with broken hairs and sometimes tender swellings, more common in children.

• Trichotillomania: hair pulling, often with irregular patches and broken hairs of different lengths.

• Scalp psoriasis and seborrhoeic dermatitis, which can cause thinning with scaling.

• Scarring alopecias: lichen planopilaris, frontal fibrosing alopecia, discoid lupus and folliculitis decalvans, with redness, burning and permanent loss.

• Secondary syphilis (moth-eaten pattern), burns, radiotherapy and injury.

• Skin tumours, which are rare.

Painful, red, scaly, pustular or shiny scarred patches, burning or itching, rapid spread, eyebrow or eyelash loss, nail changes, hair loss with a rash or joint symptoms, and patchy loss in a child with scale warrant prompt assessment.

• GP within days: scaly patches in a child, tender swellings or pus on the scalp.

• GP or dermatology within weeks: painful, red or scarred patches; rapidly spreading loss.

• GP: any unexplained patchy hair loss, for diagnosis and reassurance.

• Routine: a single smooth patch in someone otherwise well, for assessment and discussion.

The doctor asks when it began, how fast it spread, itch, pain, scaling, hair styling, pulling, family history, thyroid and autoimmune conditions, stress and medicines. They examine the patches, scalp skin, hair pull test, dermoscopy, nails and other hair-bearing areas.

• Dermoscopy: shows exclamation mark hairs, black dots and follicle openings.

• Scalp scrapings and hair plucks for fungal culture: if tinea is suspected.

• Scalp biopsy: for suspected scarring alopecia.

• Blood tests: thyroid function, full blood count, ferritin and other autoimmune markers.

• Syphilis serology if the pattern or history suggests it.

Be gentle with hair, avoid tight styles and pulling, and protect the scalp from sun. Small patches of alopecia areata often regrow without treatment. Options include topical or injected corticosteroids and newer prescribed treatments for extensive disease. Fungal infections need oral antifungal treatment. Support groups and camouflage help with the emotional impact.

The NHS route is a GP and dermatology referral. Private dermatology offers direct access to dermoscopy, biopsy and treatments including injections.