Scalp itching and dandruff

Dandruff is scaling of the scalp, often with itch, without visible inflammation. Seborrhoeic dermatitis is the inflammatory form.

Dandruff and seborrhoeic dermatitis. Dandruff is a mild, nonerythematous form with fine flakes. Seborrhoeic dermatitis has erythema, greasy yellowish scale and often affects the eyebrows, nasolabial folds, ears and central chest. They lie on one spectrum.

Mechanisms. Malassezia species break down sebum into irritant free fatty acids, with host susceptibility, abnormal stratum corneum barrier and inflammatory response. Seborrhoeic dermatitis is more frequent and severe in Parkinson disease, HIV infection, stroke and facial paralysis, and in patients with cognitive impairment or on neuroleptics.

Classification by skin findings. Scale without inflammation (dandruff, pityriasis capitis, tinea amiantacea), scale with inflammation (seborrhoeic dermatitis, psoriasis, eczema, contact dermatitis, tinea capitis), pustules or crusts (folliculitis, impetigo), and itch on normal skin (neuropathic, systemic or psychogenic).

Temporal pattern. Seborrhoeic dermatitis has peaks in infancy (cradle cap, up to 3 months), adolescence and adulthood after age 40, and worsens in winter and with stress.

Key distinctions. Sharply marginated silvery plaques extending beyond the hairline suggest psoriasis. Itch behind the ears and at the nape with nits suggests head lice. Broken hairs with scaly patches in a child suggest tinea capitis. Burning with little visible change suggests scalp dysaesthesia.

History

• Duration, itch severity, burning, pain, flaking pattern (greasy or dry), hair loss, sleep disturbance and impact on social life.
• Frequency of hair washing, products used (shampoos, conditioners, styling products, oils), recent hair dye (para phenylenediamine), perms, relaxers and hair extensions.
• Previous diagnoses: eczema, psoriasis, seborrhoeic dermatitis, asthma, atopy.
• Contacts with itchy scalp, school outbreaks, pets, sharing combs and head gear.
• Neurological disease (Parkinson disease, stroke), HIV risk, immunosuppression, diabetes, thyroid disease, kidney or liver disease.
• Neck or upper back pain, previous herpes zoster, spinal surgery (neuropathic itch).
• Mood, anxiety, fixed belief of infestation.
• Drugs: lithium, interferon, antipsychotics, EGFR inhibitors, and topical corticosteroid use.

Examination

• Distribution and morphology: fine white flakes, greasy yellow scale, thick adherent plaques, silvery well demarcated plaques, pustules, crusts, erythema, excoriations, bald patches and scarring.
• Other sites: eyebrows, glabella, nasolabial folds, ears, retroauricular area, beard, central chest, flexures, extensor surfaces, nails (pitting, onycholysis).
• Lice: live lice and nits within 1 cm of the scalp that do not slide off the hair shaft (empty shells further from the scalp do not prove active infestation). Combing wet hair with a fine toothed comb is more sensitive than visual inspection.
• Broken hairs, black dots and cervical or occipital lymphadenopathy (tinea capitis), boggy tender mass (kerion).
• Perifollicular scale and erythema with loss of follicular openings (lichen planopilaris), atrophy and follicular plugging (discoid lupus).
• Heliotrope rash, Gottron papules, shawl sign and proximal weakness (dermatomyositis).
• Bullae or erosions (pemphigus foliaceus, pemphigus vulgaris).
• Spinal tenderness and neurological findings.
• Dermoscopy: silvery white scale with red dots (psoriasis), yellowish scale with arborising vessels (seborrhoeic dermatitis), comma hairs (tinea capitis).

Red flags

• Boggy, painful scalp mass with pus, fever and lymphadenopathy (kerion).
• Scalp erythema with itch, proximal muscle weakness, dysphagia or heliotrope rash (dermatomyositis).
• Scarring, pain, pustules or progressive hair loss.
• Bullae or erosions on scalp and mouth.
• Sudden severe seborrhoeic dermatitis in an adult, especially with weight loss or other signs of HIV infection.
• Scalp itch with dermatomal sensory loss or limb weakness.
• Persistent scalp plaque that fails to respond to treatment (cutaneous lymphoma, basal cell carcinoma, discoid lupus).
• Patient believes organisms are in the skin.

Special groups

• Infants: cradle cap is benign and usually clears by 8 to 12 months. Persistent, generalised or atypical rash with failure to thrive, diarrhoea or recurrent infection needs evaluation for Langerhans cell histiocytosis, immunodeficiency and zinc deficiency.
• Children: tinea capitis, head lice and atopic dermatitis predominate. Seborrhoeic dermatitis is uncommon between 1 year and puberty.
• Pregnancy: use emollients, ketoconazole shampoo and mild corticosteroids. Avoid oral antifungals, coal tar in high strength, large area salicylic acid and ivermectin.
• Older adults: seborrhoeic dermatitis associated with Parkinson disease and cognitive impairment, and scalp neuropathic itch.
• Region specific: head lice and tinea capitis are common in crowded settings, and HIV associated seborrhoeic dermatitis is common.

Scale with or without inflammation

• Dandruff.
• Seborrhoeic dermatitis.
• Scalp psoriasis.
• Pityriasis amiantacea.
• Atopic dermatitis of the scalp.
• Pityriasis rubra pilaris.
• Dry scalp skin (xerosis).

Contact and irritant

• Allergic contact dermatitis to hair dye (para phenylenediamine), preservatives, fragrances or shampoo components.
• Irritant contact dermatitis from overwashing and chemicals.
• Photodermatitis.

Infective and infestation

• Pediculosis capitis.
• Tinea capitis, including kerion.
• Bacterial folliculitis and impetigo.
• Scabies (infants, scalp involvement).
• Herpes zoster, before and after the rash.
• Secondary syphilis.

Inflammatory and autoimmune

• Lichen planopilaris and frontal fibrosing alopecia.
• Discoid lupus erythematosus.
• Dermatomyositis.
• Pemphigus foliaceus and pemphigus vulgaris.
• Folliculitis decalvans.
• Dissecting cellulitis of the scalp.
• Lichen simplex chronicus and prurigo.

Neuropathic, systemic and psychogenic

• Scalp dysaesthesia (burning scalp syndrome).
• Cervical radiculopathy and notalgia paraesthetica spread.
• Small fibre neuropathy.
• Post herpetic itch.
• Systemic causes of generalised itch: iron deficiency, thyroid disease, diabetes, kidney disease, cholestasis, lymphoma.
• Delusional infestation.
• Neurotic excoriation.
• Trigeminal trophic syndrome.

Neoplastic and other

• Mycosis fungoides.
• Langerhans cell histiocytosis.
• Basal cell carcinoma and squamous cell carcinoma.
• Actinic keratosis.
• Zinc, biotin and essential fatty acid deficiency.

Step 1. Morphology and distribution. Examine the whole scalp, face, ears, chest, nails and skin. The diagnosis of dandruff and seborrhoeic dermatitis is clinical.

Step 2. Bedside tests

• Wet combing for lice.
• Potassium hydroxide microscopy and fungal culture of hair and scale (hair root, brush or swab) when there is hair loss, scale in a child, pustules, or no response to antiseptic shampoo.
• Dermoscopy.
• Skin swab for bacterial culture if crusted or pustular.

Step 3. Tests for persistent or atypical disease

• Patch testing with a hairdressing series for suspected allergic contact dermatitis, performed once the skin has been free of potent topical corticosteroid for 1 to 2 weeks.
• Skin biopsy (4 mm punch) for scarring, unexplained plaques, erosions, suspected cutaneous lymphoma, pemphigus (with direct immunofluorescence), lupus and psoriasis uncertain by clinical features.
• HIV test in severe, extensive or refractory seborrhoeic dermatitis, and syphilis serology when risk exists.
• Creatine kinase, ANA, myositis antibodies and muscle assessment when dermatomyositis is suspected.
• Full blood count, ferritin, TSH, glucose or HbA1c, urea, creatinine, liver tests when itch is generalised or without scale.
• Zinc level when there is periorificial or acral dermatitis.
• MRI of the cervical spine when neuropathic itch with neurological signs or red flags is present.

Limits. Scale and itch from Malassezia, psoriasis and eczema overlap, and a response to treatment is a reasonable test. Culture is slow and negative after topical antifungal use. Patch testing needs relevance to exposure. Lice cannot be excluded by a visual inspection alone.

General measures. Wash hair as often as needed (daily to twice weekly) with the active shampoo, rinse thoroughly, and avoid scratching and harsh scrubbing. Stop irritating products and allergens (hair dye, relaxer). Reduce stress where possible.

Dandruff and seborrhoeic dermatitis

• Ketoconazole 2% shampoo applied to the wet scalp, massaged and left for 3 to 5 minutes before rinsing, twice weekly for 2 to 4 weeks, then once weekly or fortnightly as maintenance.
• Selenium sulphide 2.5% shampoo, left for 10 minutes, twice weekly for 2 weeks then weekly. May discolour hair.
• Zinc pyrithione 1 to 2% shampoo 2 to 3 times weekly.
• Ciclopirox 1.5% shampoo twice weekly for 4 weeks.
• Coal tar 1 to 5% shampoo 2 to 3 times weekly (avoid on inflamed skin, in pregnancy and in children under 12 years).
• Inflammation or marked itch: mometasone furoate 0.1% lotion or betamethasone valerate 0.1% scalp application once daily for 1 to 2 weeks, then as needed (avoid prolonged use on the face). Calcineurin inhibitors (tacrolimus 0.1% ointment or pimecrolimus 1% cream twice daily) are options when corticosteroids cause atrophy.
• Thick adherent scale: salicylic acid 2 to 5% in coconut or olive oil or emollient applied overnight and shampooed off in the morning, then ketoconazole shampoo.
• Infants (cradle cap): mineral or olive oil applied for 15 to 30 minutes, gentle soft brush, then mild baby shampoo. Ketoconazole 2% shampoo or topical clotrimazole 1% twice daily for persistent cases. Hydrocortisone 1% for inflamed skin for 5 to 7 days.
• HIV associated seborrhoeic dermatitis improves with antiretroviral therapy.

Scalp psoriasis

• Clobetasol propionate 0.05% scalp application or shampoo once daily for up to 2 weeks, maximum 50 g in any week.
• Calcipotriol 0.005% with betamethasone dipropionate 0.05% scalp formulation once daily for up to 4 weeks (maximum 15 g daily and 100 g in any week of the combination; calcium monitoring if used extensively).
• Salicylic acid or coal tar to remove scale first.
• Refractory disease: dermatology for phototherapy, methotrexate, ciclosporin or biologic therapy.

Pediculosis capitis

• Dimeticone 4% lotion applied to dry hair and scalp and left for 8 hours or overnight, then washed out. Repeat after 7 days.
• Malathion 0.5% aqueous lotion applied to the dry hair and left for 12 hours (or 8 hours if specified), then washed out. Repeat after 7 days. Avoid in infants under 6 months, and in asthma if alcohol based.
• Permethrin 1% cream rinse left for 10 minutes. Resistance is frequent.
• Wet combing with a fine toothed comb every 3 to 4 days for at least 2 weeks.
• Ivermectin 200 micrograms/kg orally with food, repeated after 7 days, for refractory infestation (not for children under 15 kg or pregnancy).
• Treat household members with live lice at the same time, and launder bedding and hats at 60 C. Itch can persist for 1 to 2 weeks after cure. Children can return to school once treatment starts.

Tinea capitis. Terbinafine 250 mg orally once daily for 4 weeks (Trichophyton species) in adults, or children by weight (under 20 kg 62.5 mg, 20 to 40 kg 125 mg, over 40 kg 250 mg daily). Microsporum species: griseofulvin 15 to 20 mg/kg orally daily (maximum 1 g daily) with fatty food for 6 to 8 weeks. Add ketoconazole 2% shampoo twice weekly for 2 to 4 weeks. Reduce terbinafine to 125 mg daily if creatinine clearance is under 50 mL/min. Avoid in pregnancy.

Contact dermatitis. Identify and avoid the allergen. Mometasone furoate 0.1% scalp lotion once daily for 1 to 2 weeks. Hair dye allergy persists for life, and para phenylenediamine cross reacts with other dyes.

Bacterial folliculitis and impetigo. Chlorhexidine 4% wash, mupirocin 2% ointment 3 times daily for 5 days, or flucloxacillin 500 mg orally 4 times daily for 5 to 7 days when extensive (clarithromycin 250 to 500 mg orally twice daily if penicillin allergic).

Neuropathic scalp itch and dysaesthesia. Capsaicin 0.025 to 0.075% cream applied 3 to 4 times daily for 2 to 6 weeks if there is no open skin. Gabapentin 300 mg orally at night, increased every 3 to 7 days to 900 to 1800 mg daily in 3 divided doses (maximum 3600 mg daily; reduce for creatinine clearance 30 to 59 mL/min to 400 to 1400 mg daily, 15 to 29 mL/min to 200 to 700 mg daily, under 15 mL/min to 100 to 300 mg daily).

Amitriptyline 10 mg orally at night, increased by 10 mg each week to 25 to 75 mg (avoid in cardiac conduction disease, glaucoma, urinary retention and older adults at high risk of falls). Treat cervical spine disease. Psychological support.

Dermatomyositis and autoimmune disease. Urgent specialist referral. Prednisolone 0.5 to 1 mg/kg orally daily (maximum 80 mg daily) with steroid sparing agents, and malignancy screening.

Monitoring. Review at 2 to 4 weeks. Reassess the diagnosis if scale and itch persist after adequate treatment. Check for skin atrophy and rebound with prolonged corticosteroid use.

Referral and escalation. Dermatology within 2 weeks for scarring, bullae, lupus, dermatomyositis and mycosis fungoides, and routinely for refractory dandruff, psoriasis or contact dermatitis. Paediatric review for infants with atypical or widespread disease. Neurology or spine services for neuropathic itch with deficits. Psychiatry for delusional infestation. HIV services for severe seborrhoeic dermatitis.

Disposition. Most patients are managed in primary care. Admit for kerion with systemic illness or extensive infection. Safety net advice: return for a painful boggy scalp swelling, fever, hair loss, bullae, muscle weakness or swallowing difficulty, or persistent itch after 4 weeks of treatment.