Seborrhoeic dermatitis
Exam Tips
- If seborrhoeic dermatitis is sudden, severe, widespread, or treatment-resistant (especially beyond classic sites), think HIV and investigate appropriately.
- Key discriminator from infantile eczema: cradle cap is usually greasy with minimal itch, whereas atopic dermatitis is typically drier and markedly pruritic.
- In skin of colour, look for hypopigmented scaly plaques with subtle erythema; do not rely on bright redness alone.
- For prescribing stations: state short-duration low-potency steroid use, then maintenance with antifungal/shampoo to reduce relapse.
- Always mention safety: avoid prolonged facial/periocular steroid use and avoid potent steroids/keratolytics in young infants.
Definition
Seborrhoeic dermatitis is a chronic, relapsing inflammatory dermatosis affecting sebum-rich skin such as the scalp, face, ears, and flexures, with typically symmetrical erythema and greasy scale. In infants it most often presents in the first 3 months as cradle cap (thick scalp scale) with possible involvement of facial and nappy/flexural skin, and is usually self-limiting.
Pathophysiology
The condition is driven by an inflammatory reaction to Malassezia species in a susceptible host rather than simple fungal overgrowth alone. Malassezia hydrolyses sebum triglycerides via lipases, generating irritant free fatty acids that disrupt the stratum corneum and trigger innate and adaptive immune pathways (including cytokine-mediated inflammation). Disease expression is modulated by sebaceous activity, skin barrier vulnerability, microbiome factors, stress, climate, and immune status; this explains why antifungals improve disease and why relapse often follows recolonization.
Risk Factors
- Age peaks: infancy (<3 months), adolescence, and adults 30-60 years
- Male sex
- Immunosuppression (especially HIV infection)
- Neurological disease (for example Parkinson's disease, post-stroke states)
- Genetic syndromes (for example Down syndrome)
- Drug triggers (for example chlorpromazine, haloperidol, cimetidine, interferon-alpha, methyldopa, gold)
- Stress and environmental/climatic aggravation
Clinical Features
Symptoms
- Itch (often scalp-predominant; may be severe in inflammatory flares)
- Flaking/dandruff and recurrent visible rash
- Infants often have little or no itch despite widespread rash
Signs
- Well-demarcated erythematous patches/plaques with greasy white-yellow scale in sebaceous distribution
- Symmetrical involvement of scalp, nasolabial folds, eyebrows, glabella, retro-auricular skin, chest, and skin folds
- Scalp spectrum from dandruff to adherent yellow-brown crusting
- Eyelid margin scale/blepharitis and fissuring or crusting behind ears may occur
- In darker skin, erythema may be subtle with hypopigmented scaly patches
- Infantile disease: cradle cap (vertex/frontal thick greasy scale), facial salmon-pink flaky plaques, moist shiny fold involvement, possible nappy/truncal plaques
- Clinical image correlation: see DermNet NZ seborrhoeic dermatitis image sets (adult and infant patterns)
Investigations
Management
Lifestyle Modifications
- Explain chronic relapsing course and set expectations for maintenance therapy
- Use regular emollient/soap-substitute cleansing and gentle scale removal (especially cradle cap with softened scale and soft brush)
- Avoid irritant hair/skin products and excessive friction/scratching
- Treat secondary infection promptly and review for underlying immunosuppression if severe/widespread
- Safety: avoid forceful scale picking in infants (risk of skin damage/infection)
Pharmacological Treatment
Topical imidazole antifungals
- Ketoconazole 2% cream once or twice daily for 2-4 weeks
- Clotrimazole 1% cream two to three times daily for up to 4 weeks
- Miconazole 2% cream twice daily (useful in flexural/intertriginous disease)
First-line for many sites; reduces Malassezia load and relapse risk. Continue briefly after clearance. Avoid eye contact.
Antifungal shampoos for scalp disease
- Ketoconazole 2% shampoo twice weekly for 2-4 weeks, then once weekly or every 1-2 weeks for maintenance
- Selenium sulfide 2.5% shampoo two to three times weekly (age/licensing checks required)
Leave on scalp for several minutes before rinsing. Rotate with non-medicated shampoo for maintenance. Check product age restrictions in children.
Topical corticosteroids (short course for inflamed flares)
- Hydrocortisone 1% cream/ointment once or twice daily for up to 7 days on face/flexures
- Clobetasone butyrate 0.05% cream twice daily for short courses on trunk/scalp margins (not routine for infant facial skin)
Use lowest potency for shortest duration. Contraindications/cautions: avoid prolonged use on face, eyelids, and in infants due to atrophy, periorificial dermatitis, glaucoma risk (if periocular), and systemic absorption.
Combination anti-inflammatory plus antifungal (selected cases)
- Daktacort (miconazole 2% with hydrocortisone 1%) twice daily for up to 7 days
Useful for inflamed infected-looking flexural lesions; step down to antifungal alone once settled.
Infant cradle cap adjuncts
- White soft paraffin/liquid paraffin (50:50) to soften scale before washing
- Ketoconazole 2% shampoo/cream can be considered in persistent infantile disease under clinical supervision
Most infant cases are self-limiting; prioritize gentle de-scaling and emollients. Avoid potent topical steroids and keratolytics (for example salicylic acid) in young infants because of toxicity/irritation risk.
Complications
- Secondary bacterial infection (for example impetigo)
- Otitis externa from retro-auricular/external canal involvement
- Psychological distress and reduced self-esteem
- Rarely erythroderma in generalized severe disease
Prognosis
In infants, seborrhoeic dermatitis is usually benign and resolves spontaneously by around 8-12 months. In adolescents and adults it is typically chronic with relapsing-remitting flares, but most patients achieve good control with intermittent antifungal and short anti-inflammatory treatment.
Sources & References
🏥BMJ Best Practice(5)
💊BNF Drug References(2)
- Ketoconazole[management.pharmacological]
- Selenium[management.pharmacological]
✅NICE Guidelines(1)
- Seborrhoeic dermatitis[overview]
📖Textbook References(12)
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1654)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1544)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1638, 1639)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1637, 1638)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1637)[context]
- Oxford Handbook of Clinical Diagnosis (Huw Llewelyn, Hock Aun Ang, Keir Lewis etc.) (Z-Library).pdf(pp. 173, 174)[context]
- Oxford Handbook of Clinical Diagnosis (Huw Llewelyn, Hock Aun Ang, Keir Lewis etc.) (Z-Library).pdf(pp. 166, 167)[context]
- Oxford Handbook of Clinical Diagnosis (Huw Llewelyn, Hock Aun Ang, Keir Lewis etc.) (Z-Library).pdf(pp. 167)[context]
- [Oxford Medical Handbooks] Ian Wilkinson, Tim Raine, Kate Wiles, Anna Goodhart, Catriona Ha - Oxford Handbook of Clinical Medicine (2017, Oxford University Press) - libgen.li.pdf(pp. 416)[context]
- [Oxford Medical Handbooks] Ian Wilkinson, Tim Raine, Kate Wiles, Anna Goodhart, Catriona Ha - Oxford Handbook of Clinical Medicine (2017, Oxford University Press) - libgen.li.pdf(pp. 423)[context]
- [Oxford Medical Handbooks] Ian Wilkinson, Tim Raine, Kate Wiles, Anna Goodhart, Catriona Ha - Oxford Handbook of Clinical Medicine (2017, Oxford University Press) - libgen.li.pdf(pp. 423)[context]
- [Oxford Medical Handbooks] Ian Wilkinson, Tim Raine, Kate Wiles, Anna Goodhart, Catriona Ha - Oxford Handbook of Clinical Medicine (2017, Oxford University Press) - libgen.li.pdf(pp. 416)[context]