Hair loss

Hair loss is thinning, shedding or loss of hair from the scalp or body. The first clinical decision is whether the process is scarring or nonscarring, because scarring alopecia destroys follicles permanently and needs early treatment, while most nonscarring alopecias are reversible.

Hair cycle. The scalp holds about 100,000 hairs. Anagen (growth) lasts 2 to 7 years and holds about 85 to 90% of hairs. Catagen lasts 2 to 3 weeks. Telogen (rest) lasts about 3 months and holds 10 to 15%. Loss of up to 100 scalp hairs daily is normal.

Classification by scarring

• Nonscarring: androgenetic alopecia, telogen effluvium, anagen effluvium, alopecia areata, traction alopecia (early), trichotillomania, tinea capitis (usually), secondary syphilis, hair shaft disorders.
• Scarring (cicatricial): lichen planopilaris, frontal fibrosing alopecia, discoid lupus erythematosus, central centrifugal cicatricial alopecia, folliculitis decalvans, dissecting cellulitis, pseudopelade of Brocq, kerion and late traction alopecia.

Classification by pattern. Diffuse (telogen effluvium, anagen effluvium, diffuse alopecia areata, androgenetic alopecia in women), patterned (androgenetic alopecia: temporal recession and vertex thinning in men, central part widening with frontal preservation in women), and patchy (alopecia areata, tinea capitis, trichotillomania, discoid lupus, syphilis).

Telogen effluvium. Premature entry of anagen hairs into telogen, 2 to 3 months after a trigger. Triggers include fever, major surgery, childbirth, crash dieting, iron deficiency, thyroid disease, drugs and severe emotional stress. It resolves within 6 months of removing the trigger and does not cause total baldness.

Anagen effluvium. Abrupt shedding within days to weeks of chemotherapy, radiation or toxins (thallium, arsenic) that damage the matrix.

Key distinctions. A positive pull test with telogen roots indicates active shedding. Exclamation mark hairs indicate alopecia areata. Loss of follicular openings indicates scarring. Hair loss in a Black woman, starting at the crown and spreading outwards with scalp tenderness, suggests central centrifugal cicatricial alopecia.

History

• Onset (sudden or gradual), duration, pattern (shedding, thinning or patches), progression, itch, burning, pain, scalp scale or pustules.
• Events in the preceding 2 to 6 months: fever or acute illness, surgery, childbirth, bleeding, weight loss over 10% of body weight, crash dieting, bariatric surgery, stressful event, starting or stopping oral contraceptives.
• Hair care: tight braids, weaves, extensions, ponytails, chemical relaxers, hot combs, dyes, frequent shampooing.
• Drugs: retinoids, anticoagulants (heparin, warfarin), antithyroid drugs, beta blockers, valproate, lithium, allopurinol, statins, ACE inhibitors, antidepressants, interferon, cytotoxics, immune checkpoint inhibitors, hormonal therapy, anabolic steroids.
• Systemic symptoms: heat or cold intolerance, fatigue, heavy menstrual bleeding, diarrhoea, joint pain, rash, mouth ulcers, photosensitivity.
• Androgen excess: acne, hirsutism, irregular menses, deepening voice, clitoromegaly.
• Family history of hair loss and autoimmune disease; personal history of atopy, thyroid disease, vitiligo, syphilis exposure, HIV risk.
• Vegetarian or vegan diet, restricted diet, eating disorder, alcohol.
• Habit of pulling or twisting hair; anxiety or depression.
• Children: contacts with scalp ringworm, pets, school or sport settings.

Examination

• Pattern and extent of loss. Document with photographs and a part width measurement.
• Scalp: erythema, scale, follicular plugging, pustules, crusting, tenderness, loss of follicular openings, shiny skin, broken hairs, black dots, exclamation mark hairs, lymphadenopathy.
• Hair pull test: gently pull about 60 hairs from 3 scalp regions. More than 6 hairs (over 10%) with white bulbs is positive and indicates active shedding.
• Trichoscopy: yellow dots, black dots, exclamation mark hairs and short vellus hairs (alopecia areata), miniaturisation with hair diameter variation of over 20% (androgenetic alopecia), perifollicular scale and erythema (lichen planopilaris), comma or corkscrew hairs (tinea capitis), and broken hairs of varying length (trichotillomania).
• Wood lamp: Microsporum species fluoresce green (Trichophyton tonsurans does not).
• Eyebrows, eyelashes, body hair, nails (pits, ridging in alopecia areata), skin at other sites (psoriasis, lupus, lichen planus), thyroid, signs of androgen excess, features of iron deficiency, and weight.

Red flags

• Scalp pain, burning, erythema, pustules or loss of follicular openings (active scarring).
• Rapid onset hirsutism, virilisation or total testosterone over 5 nmol/L in a woman (androgen secreting tumour).
• Hair loss with systemic features: fever, weight loss, arthritis, rash, mouth ulcers (lupus, vasculitis, syphilis).
• Kerion: boggy, painful, pustular mass with regional lymphadenopathy in a child.
• Total or near total loss (alopecia totalis or universalis).
• Widespread loss with eating disorder or severe malnutrition.
• Rapid loss after starting a new drug or cancer therapy.
• Frontal hairline recession with eyebrow loss in a postmenopausal woman (frontal fibrosing alopecia).

Special groups

• Children: tinea capitis (most common cause in prepubertal children, especially in African populations), alopecia areata, trichotillomania, traction and telogen effluvium after illness.
• Pregnancy and postpartum: shedding 1 to 5 months after delivery, resolving over 6 to 12 months. Avoid finasteride, dutasteride, spironolactone, minoxidil and oral antifungals during pregnancy.
• Breastfeeding: avoid oral minoxidil and finasteride; use topical treatment with caution.
• Older adults: androgenetic alopecia, drug related loss, thyroid disease and nutritional causes.
• Region specific: tinea capitis and kerion, traction alopecia and central centrifugal cicatricial alopecia in women of African descent, HIV associated hair change, and protein energy malnutrition.

Nonscarring: diffuse

• Telogen effluvium (acute and chronic).
• Anagen effluvium.
• Androgenetic alopecia (male and female pattern).
• Diffuse alopecia areata.
• Iron deficiency.
• Hypothyroidism and hyperthyroidism.
• Hypopituitarism and hyperprolactinaemia.
• Polycystic ovary syndrome and other causes of androgen excess.
• Protein energy malnutrition, zinc, biotin and vitamin deficiency.
• Systemic lupus erythematosus.
• Secondary syphilis.
• HIV infection.
• Drug induced loss.
• Hair shaft disorders (trichorrhexis nodosa from chemical damage, loose anagen hair syndrome).

Nonscarring: patchy

• Alopecia areata (patchy, ophiasis, totalis, universalis).
• Tinea capitis, including kerion.
• Trichotillomania.
• Traction alopecia (early).
• Secondary syphilis (moth eaten pattern).
• Temporal triangular alopecia.

Scarring

• Lichen planopilaris and frontal fibrosing alopecia.
• Discoid lupus erythematosus.
• Central centrifugal cicatricial alopecia.
• Folliculitis decalvans.
• Dissecting cellulitis of the scalp.
• Pseudopelade of Brocq.
• Late traction alopecia.
• Scarring from burns, radiotherapy, herpes zoster, morphoea, sarcoidosis and cutaneous lymphoma.
• Kerion with scarring.
• Necrobiosis and neoplastic infiltration (basal cell carcinoma, metastasis).

Other

• Congenital hypotrichosis and ectodermal dysplasias.
• Loss of eyebrows and lashes from hypothyroidism, leprosy and alopecia areata.
• Trichotillosis from psychiatric disease.

Step 1. Scarring or nonscarring, pattern and activity. Use history, pull test, trichoscopy and pattern recognition.

Step 2. Mycology. Hair plucked with the root, scale scraped and a moistened brush or swab from the scalp for potassium hydroxide microscopy and fungal culture whenever a child has scaly hair loss, or an adult has scaly patches or pustules. Start treatment while cultures are pending when kerion or clinical suspicion is strong.

Step 3. First line blood tests for diffuse hair loss or telogen effluvium

• Full blood count and ferritin (under 30 micrograms/L indicates iron deficiency; some specialists aim for over 40 to 70 micrograms/L in hair loss, but evidence for this target is limited).
• TSH, with free thyroxine when abnormal.
• Urea, creatinine, liver tests, glucose or HbA1c.
• Vitamin B12 and folate; zinc (fasting, morning); vitamin D (benefit of correction is not established).
• HIV test and syphilis serology when risk exists or the pattern is moth eaten.
• ANA, anti dsDNA, complement and anti Ro when lupus is suspected.

Step 4. Women with androgen excess. Total testosterone, sex hormone binding globulin, free androgen index, DHEAS, androstenedione, 17 hydroxyprogesterone (in early morning, follicular phase), prolactin, LH, FSH and TSH. Pelvic and adrenal imaging when levels are markedly raised: total testosterone over 5 nmol/L or DHEAS over 18 micromol/L suggests a tumour.

Step 5. Skin biopsy. Two 4 mm punch biopsies from the active edge or an inflamed area (one for horizontal and one for vertical sections), avoiding burnt out scar. Biopsy early when a scarring alopecia is suspected. Include direct immunofluorescence when lupus is suspected. Biopsy is not needed in classical androgenetic alopecia or classical alopecia areata.

Step 6. Other tests. Trichogram or phototrichogram in uncertain cases, hair shaft microscopy for suspected hair shaft disorders, and psychiatric assessment in suspected trichotillomania.

Limits. Hair pull testing has operator variability. Ferritin is raised by inflammation. A normal blood panel does not exclude telogen effluvium, and most chronic cases have no identified cause. Fungal culture can be negative after topical antifungal use.

General measures. Remove or correct the trigger, avoid tight hairstyles, chemical relaxers and heat styling, and provide reassurance and psychological support. Counsel that regrowth is slow (about 1 cm each month). Cosmetic options include camouflage, wigs, hair fibres and scalp micropigmentation.

Telogen effluvium. Treat the trigger, correct deficiency and reassure. Regrowth usually begins within 3 to 6 months. Refer if loss lasts over 6 months (chronic telogen effluvium) or the diagnosis is uncertain. Iron deficiency: ferrous sulphate 200 mg (65 mg elemental iron) orally once daily or on alternate days for 3 months after haemoglobin normalises. Evidence that iron improves hair without anaemia is limited.

Androgenetic alopecia

• Minoxidil topical: men 5% solution or foam 1 mL twice daily (maximum 2 mL daily); women 2% solution 1 mL twice daily or 5% foam once daily. Shedding at 2 to 8 weeks is expected. Assess at 6 months and continue indefinitely, since loss recurs within months of stopping. Side effects are scalp irritation, facial hypertrichosis and, rarely, hypotension and tachycardia.
• Oral minoxidil (off label, specialist): 0.25 to 2.5 mg daily in women and 1 to 5 mg daily in men. Monitor blood pressure, heart rate, oedema and hypertrichosis. Avoid in significant cardiac disease, pericardial effusion and pregnancy.
• Finasteride 1 mg orally once daily in men. Effect starts at 3 to 6 months. Reduces PSA by about 50%, so double the PSA value during interpretation. Warn about sexual dysfunction, depression and rare persistent symptoms. Women who are or may become pregnant must not handle crushed or broken tablets. Not for women of reproductive age.
• Spironolactone 100 to 200 mg orally once daily in women with female pattern hair loss (off label). Monitor potassium and creatinine at baseline, at 4 weeks and then every 6 to 12 months. Avoid in pregnancy (contraception needed), hyperkalaemia and with potassium sparing drugs or ACE inhibitors without monitoring.
• Platelet rich plasma, low level laser and hair transplantation have variable or limited evidence and are specialist options.

Alopecia areata

• Limited patches: clobetasol propionate 0.05% or mometasone furoate 0.1% once or twice daily for 12 weeks (maximum clobetasol 50 g in any week).
• Intralesional triamcinolone acetonide 5 to 10 mg/mL in the scalp (2.5 mg/mL in the face), 0.1 mL at each site spaced 1 cm apart, every 4 to 6 weeks, maximum 20 mg at one visit. Regrowth appears in 4 to 8 weeks. Skin atrophy is the main risk.
• Extensive or refractory disease: baricitinib 2 mg orally once daily, increased to 4 mg after 12 weeks if needed (use 2 mg when eGFR is 30 to 60 mL/min; avoid below 30), or ritlecitinib 50 mg orally once daily (age 12 and over). Before starting, screen for tuberculosis and hepatitis B and C, and check full blood count, liver tests and lipids. Risks include serious infection, thrombosis, major cardiovascular events, malignancy and herpes zoster, so use with caution in older patients, smokers and those with cardiovascular risk. Avoid in pregnancy. Relapse is common after stopping.
• Contact immunotherapy with diphencyprone, methotrexate 15 to 25 mg orally weekly with folic acid 5 mg weekly on a different day, and short courses of prednisolone are specialist options with limited long term benefit.
• Psychological support is part of care. Sun protection for the exposed scalp.

Tinea capitis

• Trichophyton species: terbinafine 250 mg orally once daily for 4 weeks in adults (reduce to 125 mg daily if creatinine clearance is under 50 mL/min). Children: under 20 kg 62.5 mg daily, 20 to 40 kg 125 mg daily, over 40 kg 250 mg daily, for 4 weeks.
• Microsporum species: griseofulvin 15 to 20 mg/kg orally daily (maximum 1 g daily) with fatty food for 6 to 8 weeks, or terbinafine for 6 to 8 weeks.
• Add ketoconazole 2% or selenium sulphide 2.5% shampoo twice weekly for the first 2 to 4 weeks to reduce spore shedding.
• Check liver tests at baseline when treatment exceeds 6 weeks. Griseofulvin interacts with warfarin and oral contraceptives, and is avoided in pregnancy, porphyria and lupus. Terbinafine is avoided in pregnancy and active liver disease, and interacts with drugs metabolised by CYP2D6 (tricyclics, beta blockers, some SSRIs).
• Kerion: oral antifungal for 6 to 8 weeks (griseofulvin 15 to 20 mg/kg orally daily, maximum 1 g daily, or terbinafine 250 mg orally daily in adults), analgesia, and treatment of secondary bacterial infection when present. Avoid surgical incision. Corticosteroid has uncertain benefit.
• Examine and treat household contacts and pets. Do not share combs, hats and towels. Children may return to school once treatment has started.

Scarring alopecias

• Lichen planopilaris and frontal fibrosing alopecia: clobetasol propionate 0.05% once daily for 4 to 8 weeks, intralesional triamcinolone acetonide 10 mg/mL every 6 to 8 weeks, and hydroxychloroquine 200 mg orally twice daily (maximum 5 mg/kg of actual body weight daily) with baseline and annual retinal screening after 5 years. Add doxycycline 100 mg orally twice daily for 3 to 6 months. Oral finasteride 2.5 to 5 mg daily has been used in frontal fibrosing alopecia. Treatment aims to arrest disease, so lost hair rarely returns.
• Discoid lupus: sunscreen, clobetasol propionate 0.05% once daily, intralesional triamcinolone acetonide 5 to 10 mg/mL, and hydroxychloroquine 200 mg orally twice daily (maximum 5 mg/kg of actual body weight daily).
• Folliculitis decalvans: doxycycline 100 mg twice daily for 3 months, or rifampicin 300 mg plus clindamycin 300 mg orally twice daily for 10 weeks (maximum rifampicin 600 mg daily; check liver tests and drug interactions). Swab for Staphylococcus aureus and treat carriage.
• Central centrifugal cicatricial alopecia: stop traction and heat, topical clobetasol and doxycycline 100 mg twice daily for 3 to 6 months, and intralesional triamcinolone.
• Dissecting cellulitis: isotretinoin under specialist care, long course doxycycline and adalimumab for refractory disease.

Other causes

• Traction alopecia: stop tension from hairstyles (minimum 6 to 12 months for regrowth in early disease). Topical minoxidil 5% and topical clobetasol if inflamed; surgery in late disease.
• Trichotillomania: habit reversal training and cognitive behavioural therapy. N acetylcysteine 1200 to 2400 mg orally daily has limited evidence. Treat coexisting anxiety or depression.
• Secondary syphilis: benzathine benzylpenicillin 2.4 million units intramuscularly once; warn about Jarisch-Herxheimer reaction.
• Hypothyroidism: levothyroxine 1.6 micrograms/kg orally once daily on an empty stomach (start at 25 to 50 micrograms daily in older adults or ischaemic heart disease, increasing every 4 to 6 weeks), titrated to a normal TSH.
• Anagen effluvium from chemotherapy: scalp cooling, started before the infusion and continued afterwards, can reduce loss with solid tumours; it is not used in haematological malignancy. Regrowth follows within 3 to 6 months of finishing chemotherapy.
• Androgen excess: treat the cause (polycystic ovary syndrome: weight loss, combined oral contraceptive, spironolactone; tumour: surgery).

Monitoring. Review every 3 months for 12 months. Record photographs, pull test and part width. Reassess the diagnosis if there is no response in 6 months, and perform biopsy if scarring is suspected. Check blood pressure with minoxidil, potassium with spironolactone, liver tests with oral antifungals, and monitor laboratory parameters with Janus kinase inhibitors.

Referral and escalation. Dermatology within 2 weeks for suspected scarring alopecia, and routinely for alopecia areata that is extensive, in children, or unresponsive. Endocrinology for androgen excess. Urgent oncology and gynaecology when a tumour is suspected. Psychiatry or psychology for trichotillomania, distress or depression. Paediatric dermatology for kerion with systemic features.

Disposition. Most patients are managed as outpatients. Admit for kerion with systemic illness or when adrenal or ovarian tumour surgery is planned. Safety net advice: return for scalp pain, pustules, spreading bald areas, fever with a boggy scalp mass, new rash, or psychological distress.