Seborrhoeic Dermatitis

🔍 When to Suspect

Red skin with greasy, yellowish scales affecting seborrhoeic areas like the scalp (dandruff), face (eyebrows, nasolabial folds), ears, and central chest

From the full topic in The Ocean Library: Seborrhoeic Dermatitis

🧭 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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