Reasoning GP · Algorithm · 1-page summary
Hair loss (alopecia)
For: adults and children with hair loss in primary care. Not for: full management of pattern hair loss, tinea or eating disorders (use their own pages).
Core rule: look at the scalp in good light. Loss of follicular openings, inflammation, scale, pustules or tufting may be scarring alopecia: refer urgently before the loss becomes permanent. A normal-looking scalp does not exclude early scarring.
0Stop — call 999 now — rare in hair loss
- Suicidal thoughts with immediate risk of self-harm (ask about mood, especially on finasteride) → 999 or A&E; suicidal thoughts without immediate risk → stop finasteride, Same-day assessment.
- Otherwise the danger is irreversible scarring, kerion, a missed cancer, syphilis or an eating disorder: screen with block 2 first.
1Triage by pattern — scarring or not first
| Pattern | Think of |
|---|---|
| Scarring signs | No follicular openings, erythema, scale, pustules → LPP, frontal fibrosing alopecia, discoid lupus |
| Diffuse shedding | Trigger 2–3 months before → telogen effluvium; thyroid, iron, drugs |
| Patterned thinning | Temples + vertex (men); crown parting (women) → pattern loss |
| Patches | Exclamation-mark hairs → alopecia areata; scale, broken hairs, child → tinea |
| Broken hairs | Trichotillomania; child with distress or safeguarding concern → Urgent CAMHS |
2Screen — one row is enough
- Suspected scarring or rapidly progressive inflammatory alopecia, pustules, tufting or significant pain → Urgent dermatology, local pathway.
- Kerion: boggy painful swelling, pustules, neck nodes (especially a child) → Same-day paediatric/dermatology; do not delay systemic antifungal.
- Ulcerated or bleeding scalp lesion, fast-growing nodule, suspicious pigmented lesion → Suspected cancer skin pathway.
- “Moth-eaten” loss + rash, nodes or oral ulcers → Same-day STI clinic / GUM.
- Rapid diffuse loss + weight loss, night sweats, nodes or known cancer → Urgent investigation for malignancy.
- Very low BMI, amenorrhoea, lanugo, wasting → eating-disorder service immediately; Same-day medical review, admit if unstable.
3Assess — investigate selectively
☐ Scalp in good light ± dermatoscope ☐ Brows, lashes, beard, nails ☐ Thyroid, anaemia, androgen, lupus signs; nodes ☐ Drugs, triggers, hair care ☐ Distress, mood, suicidal thoughts
Diffuse shedding: FBC, ferritin/iron studies, TSH ± free T4. Testosterone, SHBG ± DHEAS only with hirsutism, acne, irregular periods, virilisation or suspected PCOS. Not routinely: bloods in classic male pattern loss; ANA, hormone panel, B12, zinc.
4Classify — only if the screen is negative
- Pattern hair loss — commonest, normal scalp → primary care (block 5).
- Telogen effluvium — diffuse, after a trigger → treat the cause; recovery 6–12 months or longer.
- Alopecia areata — assess extent (SALT), brows, lashes, nails, distress → topical steroid.
- Tinea capitis → systemic antifungal; screen household contacts.
- Traction — tight styles → looser styles; can scar if chronic.
- Uncertain → dermatology; never reassure suspected scarring away.
5Treat today — doses: NICE/SPC, BNF, local formulary
- Pattern loss: topical minoxidil (OTC), long-term, ≥4–6 months to respond. Finasteride 1 mg (adult men): ask about depression, suicidal thoughts, sexual dysfunction first; alert card. Spironolactone (women, off-label): consider only after assessment, preferably with specialist advice; check pregnancy, potassium, renal function, BP.
- Telogen effluvium: treat confirmed iron deficiency (ferrous sulfate 200 mg daily or alternate days), thyroid disease, B12 deficiency (NG239); do not promise regrowth.
- Alopecia areata: potent or very potent topical steroid, e.g. betamethasone valerate 0.1% or clobetasol. Tinea: oral griseofulvin or terbinafine per BNFC + antifungal shampoo.
- Distress: validate; NHS Talking Therapies, Alopecia UK; NHS wigs via hospital referral.
6Refer routinely
- Dermatology ≤18 weeks: non-severe alopecia areata not responding; uncertainty without scarring. Severe, progressive, distressing or resistant alopecia areata → Urgent
- Rheumatology: connective-tissue features, not a positive ANA alone. Endocrine: rapid virilisation or raised DHEAS → Urgent
- Adult trichotillomania: NHS Talking Therapies (habit reversal).
7Never reassure by
- A normal-looking scalp: early scarring can be subtle.
- A “receding hairline” in a postmenopausal woman: check brows, think frontal fibrosing alopecia.
- Non-specialist dermoscopy when scarring is suspected.
- A boggy scalp swelling treated with topical antifungal alone.
- A normal ferritin with inflammation: it can be falsely normal.
- A history taken without looking at brows, lashes and nails.
8Safety-net — say it, then document it
999 “If you have thoughts of harming yourself and might act on them, call 999 or go to A&E.” Same day “Contact us today if the hair loss gets rapidly worse over days or weeks, you get a painful boggy swelling or pus on the scalp (especially a child), a new sore or bleeding scalp lump, fever, weight loss or a rash, or suicidal thoughts on finasteride (stop it).”
Review: 6–8 weeks after starting iron, thyroid or tinea treatment; recheck ferritin/TSH and reassess alopecia areata at 3–4 months; telogen effluvium not resolving by 6–12 months → reassess the diagnosis. Remote: book face to face; the diagnosis needs scalp examination in good light.
✓Safe to leave primary care only if — all five, documented
No block 0–2 row applies
Scalp examined in good light; scarring excluded or referred
Brows, lashes, nails, drugs and triggers checked; bloods only if indicated
Cause named or uncertainty stated; mood and distress asked
Review booked; safety-net given
Summary of the full Reasoning GP hair loss algorithm, which holds the history, examination, differential and evidence. Sources: PCDS alopecia guidance; BAD alopecia areata living guideline (2024, updated 2025); BAD tinea capitis guideline (2014); MHRA Drug Safety Update on finasteride (2026); NICE NG145 and NG239; BSG iron deficiency (2021); NHSBSA wigs. Clinical reference — follow local safeguarding and referral pathways and check doses: NICE/SPC, BNF.