THE HUMAN SCALP AS A HABITAT FOR YEASTS 83 Candida spp., Lipomyces starkeyi, Candida zeylanoides, C. lipolytica and C. mesenterica. Their studies show that qualitatively and quantitatively the yeasts on the body are different from those in the air or from surfaces with which the body comes in contact. They concluded that the skin surface may well be a true habitat for yeasts. Croft and Black (9) also concluded that yeasts live saprophytically on normal skin. They isolated 29 yeasts from the fingertips of 22 per cent of the persons surveyed. Candida parapsilosis was the predominating organism, appearing in 12 cases. Other yeast-like organisms found were Endomyces spp., in four cases Monilia nigra, in three Cryptococcus, in two Mycoderma, in one Schizosaccharomyces hominis, in one unidentified Mortilia, in three and unknown colonies, in three. DiMenna (10) examined several areas of the body. She found that the following nonpathogenic species occurred in approximately equal numbers in the alimentary canal and in the oral cavity: Saccharomyces spp., Candida krusei, C. parapsilosis, and Torulopsis glabrata. The pathogenic C. albicans was isolated from the oral cavity in 83 per cent of the cases and from the alimentary canal in 67 per cent of the cases. The areas of the skin surveyed by DiMenna were those of the fingernails and of the arms of 120 isolates from 381 subjects. The predominating yeast-like organisms were Deb- aryomyces kloekeri, in 34 cases Cryplococcus spp., in 20 cases Rhodotorula spp., in 27 cases and the yeast-like phase of Cladosporium spp., in 22 cases. In addition, direct smears were made of the scalp to determine the presence of P. ovale. This organism was found to be present in 82 of 87 subjects examined. In only one instance was a cultural examination made of the scalp, and this was found to be negative for P. ovale. D?Menna considers that there are three possible categories of yeasts, with respect to their habit, isolated from man: 1) those that are contaminants, picked up from their surroundings and incapable of reproduction or of prolonged survival upon the human body 2) those that are capable of multiplying upon the body as well as apart from it and 3) those that are obligate parasites upon the human body. Candida albicans, P. ovale, and very possibly Torulopsis glabrata belong in the third category. Contrary to the findings of Cormell and Skinner, DiMenna concluded that the yeasts found on the skin (ex- clusive of P. ovale) and in the air are similar, both in proportions of different genera and in kinds of species. Skinner et al. (11) stated that yeasts were consistently isolated from the skin of about 50 per cent of the 275 persons who were examined. In another survey Benham and Hopkins (12) isolated 57 strains from 100 fingernail cultures, 62 from toe nails and 41 from toe webs. Sturde (13) in Germany examined the infected fingernails of 50 patients for the presence of yeasts. In each instance one or more yeasts were iso- lated. Those predominating were C. albicans, C. parapsilosis, and Toru-

84 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS lopsis famata. The most complete study to date on the distribution of yeasts in the human body has been made by Rieth (14) also in Germany. Over 15,000 patients were studied during a four year period. From the skin, hair and nails almost 2000 yeasts were identified. Those predomi- nating were C. albicans, C. parapsilosis, Torulopsis famata, Trichosporon cutaneum, Rhodotorula mucilaginosa and Rh. rubra. Kapica and Blank (15), Fischer (16), Nino et al. (17) all claim repeated isolation of C. parapsilosis from infected nails showing typical signs of moniliasis. Kapica and Blank furthermore have carried out studies to prove that C. albicans (18) and C. parapsilosis (15) are both capable of utilizing nitrogen obtained solely from keratin, provided glucose is present as an initial stimulus. These workers admit that while such a biochemical investigation cannot provide an answer to the question of pathogenicity of C. albicans and C. parapsilosis its results indicate a reason for the pathogenicity. They found that this keratin breakdown occurs between 40 and 56 days. As far as the references to the scalp flora are concerned Ota and Huang (19) simply report "ordinary" yeasts in addition to the organism they be- lieved to be P. ovale. MacKee and Lewis (20) showed that the scalp yields numerous fungi and yeasts as well as bacteria but made no attempt to identify them. Benham (21) isolated a number of yeast-like organisms which she placed in the genus Cryptococcus. In several instances, more- over, isolates from the scalp reported to be P. ovale were later shown by her also to be members of the genus Cryptococcus. Similarly, Spoor et al. (22) in their isolation studies of P. ovale from normal and seborrheic subjects have isolated not only this organism in approximately 60 per cent of the cases but speak also of unidentified strains which are classified as "yeast- like" types. EXPERIMENTAL METHODS Two groups of individuals were studied. They consisted of 98 members of the senior class of the Massachusetts College of Pharmacy from Septem- ber, 1958, to June, 1959, and 91 members of the senior class from Septem- ber, 1959, to January, 1960. Included in these groups were 17 females. The members of both groups ranged in age between twenty and thirty years. The material used in this study from which the isolation of yeasts was made is commonly known as "scurf." Scurf represents desquamated epithelial cells from the scalp together with accumulated secretions, acquired soil, and a mixed microbiological flora. With all subjects it was possible to obtain a sample of scurf by instructing each one to brush his scalp vigorously and to collect the material on appropriate cul- ture media. No attempt was made to record the degree of sloughing off or subsequently to correlate the amount of scurf with the type of organism