GPAtlas🧭 When to suspect
Seborrhoeic dermatitis is a common, chronic or relapsing inflammatory dermatosis affecting the sebaceous-gland-rich regions of the body – the scalp, face and central chest. The hallmark is greasy, yellowish scale sitting on ill-defined erythema. It is thought to represent an inflammatory reaction to commensal Malassezia yeast, which lives on everyone's skin, so it is neither contagious nor a sign of poor hygiene. It affects roughly 3–12% of the population.
There are two distinct forms. Infantile disease (“cradle cap”) appears in the first months of life and is usually self-limiting, resolving by 6–12 months. Adult disease begins in late adolescence, is commoner in men, and runs a relapsing course with characteristic winter flares and triggers such as stress and fatigue. Dandruff (pityriasis capitis) is the mild, non-inflamed scalp form.
The key primary-care skill is to recognise the pattern clinically (no test is needed in typical cases), treat the yeast and the inflammation, and stay alert to the minority who need more – in particular, sudden, severe or treatment-resistant disease as a clue to immunosuppression.
| Form | Typical distribution & features |
|---|---|
| Infantile (cradle cap) | Thick, greasy, yellow scalp crust ± salmon-pink napkin/flexural patches; the baby is typically content and untroubled; self-limiting by 6–12 months. |
| Adult | Erythema with greasy scale at the scalp, eyebrows, glabella, nasolabial folds, ears/retroauricular skin, beard and central chest; chronic and relapsing. |
| Dandruff (pityriasis capitis) | Diffuse, fine, bran-like scalp flaking without erythema – the mild, non-inflamed end of the spectrum. |
Raise suspicion particularly in adolescents and young adults, and again in older adults, and consider the recognised associations – HIV/immunosuppression, Parkinson's disease, neuroleptic medication and Down syndrome.
Source: DermNet
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