Key Facts

Alopecia is a common presentation with diverse aetiologies. The initial clinical assessment should determine whether the hair loss is scarring or non-scarring, as this fundamentally changes the differential diagnosis and urgency of management.

Epidemiology

• Androgenetic alopecia: affects ~50% of men by age 50, ~40% of women by age 70
• Alopecia areata: lifetime prevalence ~2%
• Telogen effluvium: very common; often post-partum or post-illness
• Scarring alopecias: uncommon but important — ~3–7% of hair clinic referrals

Aetiology — Non-Scarring

• Androgenetic alopecia: genetic + hormonal (DHT); most common
• Telogen effluvium: diffuse; triggered by physiological stress
• Alopecia areata: autoimmune T-cell attack on hair follicle
• Tinea capitis: fungal; children predominantly
• Traction alopecia: hairstyling practices
• Drugs: chemotherapy (anagen effluvium), anticoagulants, retinoids, antithyroid drugs

Aetiology — Scarring

• Lichen planopilaris / frontal fibrosing alopecia: lymphocytic scarring alopecia
• Discoid lupus erythematosus: autoimmune; erythematous plaques, follicular plugging
• Central centrifugal cicatricial alopecia: most common scarring alopecia in Black women
• Dissecting cellulitis of scalp: inflammatory, neutrophilic

Pathophysiology

• Non-scarring: follicle preserved — regrowth possible
• Scarring: inflammatory destruction of hair follicle stem cell bulge region → replaced by fibrous tissue → permanent loss

Androgenetic Alopecia

• Males: bitemporal recession → vertex thinning → eventual confluence (Hamilton-Norwood classification)
• Females: diffuse thinning over crown with preserved frontal hairline (Ludwig classification)
• Gradual onset; no inflammation

Telogen Effluvium

• Diffuse shedding 2–3 months after trigger
• Positive pull test
• No patches; no scarring
• Triggers: childbirth, major illness, surgery, crash dieting, drugs, thyroid dysfunction, iron deficiency

Alopecia Areata

• Well-circumscribed patches of complete hair loss
• 'Exclamation mark' hairs at periphery (tapered proximal end)
• Smooth, non-scarred scalp
• Nail pitting may be present

Scarring Alopecia Features

• Loss of follicular ostia (openings) — key sign
• Perifollicular erythema, scale, or pustules
• Patches of permanent hair loss

Red Flags

• Scarring alopecia — needs urgent dermatology referral (irreversible if untreated)
• Sudden, rapid hair loss with systemic symptoms — consider SLE, secondary syphilis
• Hair loss in children — consider tinea capitis
• Trichotillomania — psychological assessment needed

Bedside

• Pull test: gently pull ~60 hairs — >6 hairs extracted suggests active shedding
• Dermoscopy (trichoscopy): miniaturised hairs (androgenetic), exclamation mark hairs (alopecia areata), comma/corkscrew hairs (tinea), perifollicular scale (lichen planopilaris)

Bloods

• Ferritin: iron deficiency (aim >50 μg/L for hair health)
• TFTs: thyroid dysfunction
• FBC, CRP: systemic inflammation
• ANA, dsDNA: if SLE/discoid lupus suspected
• Syphilis serology: if moth-eaten alopecia or risk factors
• Testosterone, DHEA-S, SHBG: in women with androgenetic alopecia + features of hyperandrogenism
• Vitamin D, zinc: may contribute to hair loss

Biopsy

• Scalp biopsy (4 mm punch, horizontal section): gold standard for scarring alopecias — distinguishes lichen planopilaris, discoid lupus, etc.
• DIF on biopsy: may show lupus band in discoid LE

Special Tests

• Fungal culture: if tinea capitis suspected
• Trichogram: microscopic hair analysis (rarely done clinically)

Non-Pharmacological

• Reassurance: particularly for telogen effluvium (self-limiting)
• Address triggers: iron replacement (if ferritin <50), thyroid correction, drug review
• Avoid traction: change hairstyles if traction alopecia
• Wigs/hairpieces: can be prescribed on NHS for alopecia areata/totalis
• Psychological support: hair loss significantly impacts mental health

Pharmacological — Androgenetic Alopecia

• Minoxidil 5% solution/foam: topical, BD (men) or OD (women); takes 3–6 months; must continue indefinitely
• Finasteride 1 mg OD (men only): 5-alpha reductase inhibitor; reduces DHT; takes 3–6 months; risk of sexual side effects (~2%); contraindicated in women of childbearing age
• Spironolactone 100–200 mg OD: anti-androgen for female pattern hair loss (off-licence)

Pharmacological — Telogen Effluvium

• Treat underlying cause: iron replacement, thyroid correction
• Self-limiting: hair regrows within 6–12 months once trigger removed

Pharmacological — Scarring Alopecia

• Potent topical corticosteroids: first-line for lichen planopilaris, discoid LE
• Hydroxychloroquine 200 mg BD: for lichen planopilaris and discoid LE
• Intralesional triamcinolone: for active lichen planopilaris
• Goal: halt progression (scarring is permanent)

Surgical

• Hair transplantation: for stable androgenetic alopecia — specialist referral

Referral Criteria

• Dermatology: all suspected scarring alopecia (urgent), diagnostic uncertainty, treatment-resistant alopecia areata
• Psychology: significant impact on mental health, trichotillomania

• Androgenetic alopecia: progressive without treatment; stabilised/improved with minoxidil and finasteride
• Telogen effluvium: self-limiting — full regrowth expected within 6–12 months
• Alopecia areata: ~50% recover within 1 year; worse prognosis if extensive, ophiasis pattern, childhood onset
• Scarring alopecia: irreversible once follicle destroyed — early treatment halts progression
• Psychological impact: significant — associated with depression, anxiety, social withdrawal

Alopecia Classification

Drug-Induced Hair Loss