Differences between intrafollicular microorganism profiles in perioral and seborrhoeic dermatitis.

Although often associated with overuse of topical corticosteroids, perioral dermatitis seems to develop seldom in patients with typical seborrhoeic dermatitis in spite of long-term application of corticosteroids. In order to compare the profiles of intrafollicular microorganisms in the lesions of perioral and seborrhoeic dermatitis, tape-stripped samples were obtained from eight lesions of perioral dermatitis, 10 lesions of seborrhoeic dermatitis, and the perioral skin of 31 normal subjects. After staining with Toluidine blue, resident microorganisms on plucked hair roots were evaluated microscopically. In all patients with perioral dermatitis and two normal subjects, 20-70% of sample hairs were positive for fusiform bacteria regarded as fusobacteria. Malassezia-positive hairs were rarely seen in these cases. Seborrhoeic dermatitis showed the opposite results. Perioral dermatitis may tend to develop under fusiform-bacteria-rich conditions, rather than Malassezia-rich conditions as in the case of seborrhoeic dermatitis.