International Academy of Cosmetic Dermatology
It is a condition that comes and goes and is frequently associated with dandruff and seborrhea (oiliness) on the scalp. The estimated prevalence of SD is 1-5%. SD can occur in adolescents, but there is a peak incidence in adults. It can also occur in infancy as “cradle cap”.
The cause of SD has never been clear, but it appears to correlate with three factors: the yeasts of the Malassezia sp, sebaceous lipids, and individual susceptibility. Sebaceous gland secretions provide the substrate for the yeasts to proliferate. In addition, individuals with SD have an underlying defect in the permeability barrier that enables the fatty acids from the sebum to penetrate and to cause the resulting flaking and itching.
SD of the scalp can be confused with other diseases. It can be differentiated from psoriasis in which the scales are usually thicker and red plaques may for found elsewhere, particularly on the elbows and/or knees. Rosacea and SD are often confused and may coexist. Telengiectasia and papules on the cheeks indicate a diagnosis of rosacea, whereas redness and scaling on both the scalp and paranasal areas are suggestive of SD.
Prevention of SD involves the avoidance of occlusive agents such as Vaseline®. Treatment includes shampooing of the scalp with agents containing tar, selenium sulfide, zinc pyrithione, or corticosteroids Corticosteroid solution or foam can also be used when itching is prevalent. Elsewhere on the body, topical corticosteroids, ketaconazole cream, or selenium sulfide foam can be used.
Jennifer L. Parish, MD