Classic seborrheic dermatitis during adolescence is typically localized to the scalp. The mild form is commonly known as dandruff, a fine, white, dry scaling of the scalp with minor itching. Additional findings of seborrheic dermatitis vary from diffuse, brawny scaling to focal areas of thick, oily, yellow crusts with underlying erythema. The external auditory canals, eyebrows, eyelids, and intertriginous areas may be involved as well. Pruritus may be minimal or severe.
Figure 192-1 Seborrheic dermatitis (cradle cap).
Laboratory studies and imaging studies are not necessary todiagnose seborrheic dermatitis. Fungal cultures and potassiumhydroxide studies may be necessary to help differentiate seborrheic dermatitis of the scalp from tinea capitis (see Chapter 98).
Seborrheic dermatitis in an infant may be difficult to differentiate from atopic dermatitis, and in fact, some cases may represent an overlap. In a teenager, seborrheic dermatitis of the scalpand psoriasis of the scalp may have very similar clinical findings; it may be very difficult to differentiate the two disorders,especially if there are no other cutaneous findings to provideadditional clues. Intractable, severe, generalized seborrheicdermatitis suggests Langerhans cell histiocytosis. Intractableseborrheic dermatitis, accompanied by chronic diarrhea andfailure to thrive, suggests Leiner disease or acquired immunodeficiency syndrome (AIDS).
Seborrheic dermatitis of the scalp is usually asymptomatic andgenerally does not require treatment. Minor amounts of scalecan be removed easily by frequent shampooing. For infantswith cradle cap, oil (such as mineral oil or olive oil) may begently massaged into the scalp and left on for a few minutesbefore gently brushing out the scale and shampooing. Dailyshampooing with ketoconazole, zinc pyrithione, selenium sulfide, or salicylic acid shampoos can treat scalp scale. Seborrheicdermatitis with inflamed lesions responds rapidly to treatmentwith low-potency steroids two times daily.
The response to treatment is usually rapid. Secondary bacterial infection can occur but is uncommon. Intractable disease and other complications warrant further evaluation for other etiologies.
Cradle cap is self-limited and resolves during the first year of life. Seborrheic dermatitis does not cause permanent hair loss.
For teenagers, continued use of an antiseborrheic shampoo is often required for control of dandruff.
Frequent shampooing, especially with early signs of seborrheic dermatitis, may help prevent progression.