Hair loss by pattern
A practical separation of shedding, patterned, patchy and scarring alopecia.
Updated: 2026-09-13
Written for clinicians and medical students
This section is a teaching reference for doctors, residents and medical students. It is not patient guidance and not a substitute for clinical examination, and it must not be used for self treatment.
Four clinical pathways
- Diffuse shedding with preserved density pattern suggests telogen effluvium; ask about illness, childbirth, weight loss, iron deficiency, thyroid disease and medicines 2 to 4 months earlier [1].
- Frontotemporal or vertex miniaturisation suggests androgenetic alopecia. Dermoscopy shows hair shaft diversity and increased single-hair follicular units [1].
- Smooth patches with exclamation-mark hairs, black dots or nail pitting support alopecia areata; scale and broken hairs instead raise tinea capitis [2].
- Loss of follicular openings, perifollicular scale, erythema, pustules or atrophy indicates scarring alopecia and needs prompt specialist assessment and biopsy from an active margin.
Targeted work-up
- Use hair pull testing and dermoscopy to define activity and pattern. Fungal microscopy and culture are essential when tinea is possible.
- Order laboratory tests only when history or examination supports a cause, commonly blood count, ferritin and thyroid testing in diffuse shedding.
- Biopsy uncertain scarring alopecia before advanced disease destroys diagnostic follicles; request horizontal and vertical sections where available.