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Seborrhoeic dermatitis
Seborrhoeic dermatitis is a chronic relapsing inflammatory reaction to Malassezia yeasts in sebaceous-rich areas — scalp, eyebrows, nasolabial folds, behind the ears and the chest — and is treated with topical antifungals and short courses of mild steroids.
Why it matters in the exam
The exam shows an adult with greasy yellowish scale and redness in the nasolabial folds and eyebrows, or a baby with "cradle cap", and asks for the treatment. The more important question is when seborrhoeic dermatitis is a clue to another disease: a severe widespread form appears in HIV and Parkinson disease, and in a baby with a resistant rash in the folds and scalp together with petechiae and organomegaly, Langerhans cell histiocytosis must be considered. Also asked is the distinction from scalp psoriasis (thick well-defined plaques that extend beyond the hairline), from lupus (which spares the nasolabial folds) and from rosacea. Remember that the disease is chronic and relapsing and that the aim is control, not cure, so an antifungal shampoo is used once or twice a week even after clearing. On the face, long-term steroids are best avoided because of atrophy and perioral dermatitis, and calcineurin inhibitors or antifungals are used. Stress, fatigue and cold dry weather also worsen the disease.
Key points
- Seborrhoeic dermatitis is a chronic relapsing inflammatory reaction to Malassezia yeasts in sebaceous-rich areas.
- It appears in infants as cradle cap and in adults as redness and scale in the nasolabial folds, eyebrows and scalp.
- Treatment is topical antifungals such as ketoconazole, with a short mild steroid or a calcineurin inhibitor on the face.
- A severe widespread form appears in HIV and Parkinson disease and requires investigation.
- In a baby with a resistant rash and petechiae, Langerhans cell histiocytosis must be excluded.
Summary table
| Age or setting | Appearance | Differential diagnosis | Treatment |
|---|---|---|---|
| Infants — cradle cap | Greasy yellowish scale on the scalp, sometimes in the folds, no itch | Atopic dermatitis, Langerhans cell histiocytosis | Oil to soften the scale, mild shampoo; clears by about one year |
| Adults — face | Redness and scale in the nasolabial folds, eyebrows and glabella | Rosacea, lupus (spares the folds) | Ketoconazole 2% cream; mild steroid for a few days; calcineurin inhibitors |
| Adults — scalp | Diffuse scale, itch, "dandruff" | Psoriasis, tinea capitis | Ketoconazole, selenium sulfide or ciclopirox shampoo; then once weekly for maintenance |
| HIV and Parkinson disease | Severe, widespread and resistant form | — | Treat the underlying disease; HIV test in a severe sudden form |
| Erythroderma in an infant | Widespread rash with diarrhoea and failure to thrive | Immunodeficiency (Leiner syndrome) | Urgent immune work-up |
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Sources
- British Association of Dermatologists patient and clinical guidance on seborrhoeic dermatitis, 2021 — Treatment
- European Dermatology Forum guideline on topical antifungals, 2020 — Ketoconazole and ciclopirox
- CDC/NIH/IDSA Guidelines for the prevention and treatment of opportunistic infections in adults with HIV, 2024 — Skin manifestations
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.