Pityriasis Folliculorum (Demodex)

Pityriasis folliculorum (Demodex) represents an apparent clinical entity no previous mention of which could be discovered in a careful search of the current textbooks on dermatology and of the dermatologic literature during the past twenty years. It is with some misgivings that the author attributes a pathogenic rôle toDemodex folliculorumin the face of an overwhelming opinion to the contrary due to the repeated finding of the parasite in the sebaceous ducts of many persons with normal skins. In fact, some authors have stated that the parasite occurs in the hair follicles or sebaceous ducts of nearly all adults. By analogy with other disorders, however, this ubiquity of the demodex should not be considered an unanswerable argument against its assuming pathogenicity under certain circumstances. It is a familiar fact that althoughStaphylococcuscan be cultured from apparently normal skins, it may at times cause disease. The common bacteria of