THE HUMAN SCALP AS A HABITAT FOR YEASTS* BY FRANK C. ROIA, JR., M.S., RAYMOND W. VANDERWYK, PH.D., and JOHN A. BEAt,, M.S.t Presented September Z9, Z962, Seminar, New York City' INTRODUCTION AND BACKGROUND ALMOST from the very moment when Rivolta (1) in It'aly in 1873 first isolated and described the yeast organism, Pilyrosporum ova/e from the human scalp, the etiological role of this organism in seborrheic dermatitis and pityriasis capitis has been a matter of much dispute. On the one hand, its universal presence in dandruff scales in numbers proportional to the severity of the condition has been verified by every worker interested in the problem. On the other hand, the lack of convincing evidence to prove pathogenicity through animal or human inoculation has led to the modern supposition that P. ovale is an inoffensive saprophyte of man. Some investigators, however, argue that this organism more nearly behaves as a true parasite. It has been isolated nowhere but from the animal skin. It is extremely fastidious in its growth habits, requiring naturally occurring fatty acids together with a source of nitrogen and glucose. Each of these nutrients is supplied by the skin. Stained smears of the scalp usually reveal many actively budding forms. In addition to the possible role of Pityrosporum ovale in seborrheic der- matiris and pityriasis capiris, an etiological relationship to seborrheic blepharitis and dermatitis of the eyelids has been suggested by Gots (2) and his co-workers. In their studies budding yeast forms morphologically similar to P. ovale were found in 100 per cent of 143 cases of seborrheic blepharitis. They were also able to demonstrate sensitization of the organism by intradermal skin tests and have indicated that inflammatory lesions of the conjunctiva are allergic in character, irrespective of the role of the organism in seborrheic dermatitis. More recently, Gordon (3) has described a new species of Pilyrosporum which he has named P. orbicu/are because of its spherical shape. The organism was isolated from 15 of 18 cases diagnosed as tinea versicolor. Because of its lipophilic nature it seems to be related to P. ovale. Attempts * Research suyported by a grant from John H. Breck, Inc. } Dept. of Microbiology 'Massachusetts College of Pharmacy, Boston 15, Mass.

82 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS at experimental inoculation have failed to produce tinea versicolor in humans. It is interesting to note that the organism described by Gordon is morphologically identical to the so-called spherical forms of P. ovale found by Gots in lid-margin scrapings from cases of seborrheic blepharitis. The authors of this paper became interested in the yeast flora of the human scalp while working with improved culture media for isolating and growing P. ovale. Isolation studies showed that P. ovale, while prevalent, is not the only yeast organism of the scalp. The possibility occurred to us that since P. ovale could not definitely be linked to dandruff, perhaps some other, as yet undiscovered, yeast could be a contributing factor. We therefore decided to survey a large number of humans in the hope of relating the scalp yeast flora to possible pathogenicity. The literature makes many references to the isolation and identification of yeasts from various areas of the body in both normal and pathological conditions but only an occasional reference to the human scalp. Surveys on the yeast flora of the external surface, the nails, the orifices and the alimentary canal have been carried out. At least three factors seem to be responsible for this interest. 1. New and improved media have been formulated for the isolation and study of yeasts, which have resulted, for example, in the realization of the obligate lipophilic nature of Pilyrosporum ovale (4). The introduction of certain antibiotics into culture media has facilitated the isolation of yeasts without interference by bacterial overgrowth. 2. The monograph of Lodder and Kreger-Van Rij (5) and the contribu- tions of Wickerham (6) have created a better understanding of the taxon- omy of yeasts. 3. A number of infections attributed to members of the yeast group have been reported. Many species of Candida and Cryptococcus are being isolated with increasing frequency from a variety of lesions in man, al- though Candida albicans and Cryptococcus neoformans have been considered to be the only pathogenic members of the group. The widespread use of antibiotics is responsible in no small part for the increase in candidiasis and cryptococcosis. Huxley and Hurd (7) isolated from the skin and described a number of pink yeasts belonging to the genus Rhodotorula and Sporobclomyces. The skin areas selected for study were those between the toes, between the fingers, and from the lumbar region, the axilla, the inframammary region and the navel. They found the predominant organism to be Rhodotoru/a mucilaginosa. Connell and Skinner (8) determined the occurrence of non- fermenting, nonpigmented yeasts on 250 human subjects. Of 784 isolates of yeasts and yeast-like fungi the following species are recorded as having been isolated. They are given in the order of their frequency: Cryptococcus diafluens, Cr. aerius, Cr. albidus, Cr. laurentii, var. fiavescens, Cr. rotundatus,