ESSENTIALS OF DIAGNOSIS
Dry scales and underlying erythema.
Scalp, central face, presternal, interscapular areas, umbilicus, and body folds.
Seborrheic dermatitis is an acute or chronic papulosquamous dermatitis that often coexists with psoriasis and is associated with inflammation due to Malassezia species.
The scalp, face, chest, back, umbilicus, eyelid margins, genitalia, and body folds have dry scales (dandruff) or oily yellowish scurf (Figure 6–10). Pruritus is a variable finding. Patients with Parkinson disease, HIV-infected patients, and patients who become acutely ill often have seborrheic dermatitis.
Close-up of seborrheic dermatitis showing flaking skin and erythema around the beard region. (Reproduced with permission from Richard P. Usatine, MD in Usatine RP, Mayeaux EJ Jr, Chumley HS. The Color Atlas and Synopsis of Family Medicine, 3rd ed. McGraw-Hill, 2019.)
There is a spectrum from seborrheic dermatitis to scalp psoriasis (eFigure 6–18). Extensive seborrheic dermatitis may simulate intertrigo in flexural areas, but scalp, face, and sternal involvement suggests seborrheic dermatitis.
A. Seborrhea of the Scalp
Shampoos that contain zinc pyrithione or selenium are used daily if possible. These may be alternated with ketoconazole shampoo (1% or 2%) used twice weekly. A combination of shampoos is used in refractory cases. Tar shampoos are also effective for milder cases and for scalp psoriasis. Topical corticosteroid solutions or lotions are then added if necessary and are used twice daily. (See treatment for scalp psoriasis, above.)
B. Facial Seborrheic Dermatitis
The mainstay of therapy is a mild corticosteroid (hydrocortisone 1%, alclometasone, desonide) used intermittently and not near the eyes. If the disorder cannot be controlled with intermittent use of a mild topical corticosteroid alone, ketoconazole 2% cream is added twice daily. Topical tacrolimus and pimecrolimus are steroid-sparing alternatives.
C. Seborrheic Dermatitis of Nonhairy Areas
Low-potency corticosteroid creams—ie, 1% or 2.5% hydrocortisone, desonide, or alclometasone dipropionate—are highly effective.
D. Seborrhea of Intertriginous Areas
Apply low-potency corticosteroid lotions or creams twice daily for 5–7 days and then once or twice weekly for maintenance as necessary. Selenium lotion, ketoconazole, or clotrimazole gel or cream may be a useful adjunct. Tacrolimus or pimecrolimus topically may avoid corticosteroid atrophy in chronic cases.
E. Involvement of Eyelid Margins
“Marginal blepharitis” usually responds to gentle cleaning of the lid margins nightly as needed, with undiluted baby shampoo or eyelid cleanser using a cotton swab.
The tendency is for lifelong recurrences. Individual outbreaks may last weeks, months, or years.