Correlation of Pityosporum ovale density with clinical severity of seborrheic dermatitis as assessed by a simplified technique.

One hundred patients with facial seborrheic dermatitis and 42 control subjects were studied. The number of periodic acid-Schiff-positive Pityosporum ovale yeast cells in skin scrapings per high-power field were counted and designated 1 + to 4 +. Our data indicate a correlation between the density of P. ovale and the clinical severity of seborrheic dermatitis, both before and after therapy with a precipitated sulfur/salicyclic acid shampoo. The data support the concept that yeast contributes to the pathogenesis of seborrheic dermatitis.