Dandruff & Scalp Dermatitis
Dandruff and scalp seborrheic dermatitis are related conditions on a spectrum of scalp flaking and irritation, reviewed by AAFP and in the New England Journal of Medicine.
Symptoms
Flaking and itching of the scalp, ranging from dry white flakes (dandruff) to greasy yellow scale with redness (seborrheic dermatitis), sometimes extending to the eyebrows, sides of the nose, and ears.
Causes and risk
Overgrowth of Malassezia yeast interacting with sebum production and individual immune response drives both conditions, per Cochrane review data; it is more severe in people who are immunocompromised.
How it is evaluated
Diagnosis is clinical based on the characteristic distribution and appearance; biopsy is rarely needed.
Treatment
Medicated shampoos -- zinc pyrithione, selenium sulfide, ketoconazole, or ciclopirox -- left on the scalp for about 5 minutes are first-line, with ketoconazole showing a number needed to treat of 5 versus placebo per AAFP treatment guidance; a step-down maintenance schedule prevents recurrence.
When to seek care
Signs of secondary infection, fever, a rapidly spreading rash, or treatment failure -- especially in someone immunocompromised -- warrant prompt evaluation.