Skin biopsies may effectively distinguish seborrheic dermatitis from similar disorders. Seborrheic dermatitis should have neutrophils in the scale crust at the margins of follicular ostia. AIDS-associated seborrheic dermatitis more commonly presents as parakeratosis, a few individually necrotic keratinocytes within the epidermis, and plasma cells in the dermis. Yeast cells sometimes are visible within keratinocytes on special stains. If hyphae are present, dermatomycosis is the diagnosis. Shorter hyphae with spores (“spaghetti and meatball pattern”) are present with tinea versicolor. 8
Basic treatment consists of using shampoos containing zinc pyrithione (Head and shoulders, ZNP bar), selenium sulfide (Selsun blue and prescription strength Selsun) or ketoconazole (Nizoral AD and prescription strength Nizoral). A person may need to try several shampoos to find the one that works best, and then rotate between several medicated and non-medicated shampoos to maintain effectiveness. It's important to massage the shampoo onto the scalp and other affected areas and leave it in place for a few minutes before rinsing thoroughly. Other shampoo ingredients that are sometime helpful are salicylic acid, coal tar, and sulfur.