Seborrheic dermatitis of the scalp: etiology and treatment.

Seborrheic dermatitis is a common chronic infection of the lipid-rich areas of skin. While seborrheic dermatitis has been a recognized clinical entity for decades, its etiology is far from clear. Early investigators of the development of seborrheic dermatitis focused on the role of the Malassezia (previously Pityrosporum) yeasts. These yeasts are also normal skin commensals, thus their importance as pathogens in this disorder came to be doubted. However, it was subsequently found that treatment of seborrheic dermatitis with an antifungal agent not only resulted in clinical improvement but also reduced the number of Malassezia yeasts on the skin. This has resulted in a resurgence of interest in the Malassezia yeasts. It has been hypothesized that there is an immunological component to seborrheic dermatitis, possibly representing an abnormal host response to the Malassezia yeasts. This paper will discuss the role of Malassezia in the etiology of seborrheic dermatitis, as well as the various treatment options.