J. Soc. Cosmet. Chem., 22, 187-198 (March 4, 1971) Model System for of Dandruff the investigation JOHN A. TROLLER, Ph.D.* Synopsis--A model system has been described for the production of a DANDRUFF-like syn- drome on GUINEA PIGS. This syste•n, in addition to SCALP ORGANISMS, requires the presence of a LIPID mixture. The sloughing reaction observed is probably due to the liberation of free FATTY ACIDS and the relative amount of Cts MONOENOIG AGID in- crease at the irritated site. The replacement of the microbial moiety of the test system with a G•s monoenoic acid (oleic) also produces a similar type of desquamation and strongly sug- gests that this or a similar compound may be responsible for the sloughing reaction. INTRODUCTION The noninflammatory, scaling desquamation of the horny layers of the human scalp, commonly known as dandruff, has been under in- vestigation for a considerable period of time. Despite the plethora of investigational effort which has been devoted to this disease, there re- mains much disagreement concerning its etiology. One of the major obstacles to definitive investigations of the etiologi- cal aspects of dandruff has been the lack of a suitable and meaningful ex- perimental model. Previous attempts to use humans and/or laboratory animals for this purpose have met with only indifferent success. Although humans have been used as test animals for numerous stud- ies, they possess certain, inherent disadvantages as suitable subjects, the greatest of which is the almost universal occurrence of dandruff. This ubiquity dictates that the scalp must be "cleared" of naturally occurring dandruff by artificial means before test conditions can be imposed upon it, thus creating a less than desirable experimental model (1). * Miami Valley Laboratories, Procter 8c Gamble Co., P.O. Box 39175, Cincinnati, Ohio 45239. !87

188 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Kile and Engman (2) described studies in which they inoculated hu- xnans with live and killed Pityrosporum ovale, an organisxn commonly implicated as the causative agent of dandruff (3). The most extensive scaling was produced by rubbing a viable culture of P. ovale on the in- tact scalp skin. Other workers (4, 5) have also inoculated humans and xvith at least some success however, as Rocha et al. (6) point out, there seems to be considerable doubt concerning the identification of the fun- gus used in these studies. Emmons (1) states that the trauma incident to intracutaneous injection and scarification, which was a characteristic of many of the preceding studies, often results in some scaling and pig- mentation without the inoculation of scalp organisms. Therefore, in- terpretation of data from many of these studies is difficult. In studies with a confirmed culture of P. ovale inoculated on the scalp and back of test subjects, Emmons could not show the presence of lesions on the back and could demonstrate no increase in the severity of scalp lesions. From these data, he concluded that P. ovale is a saprophyte of the scalp with no etiological significance in seborrhea. Rocha et al. (6) applied P. ovale in a lanolin paste to scarified and nonscarified areas of human backs and also injected suspensions of live P. ovale cells intradermally into the same skin areas. In all cases, after a short incubation period character- ized by erythema and induration, these symptoms disappeared with no further reaction or scaling. Martin-Scott (7) applied P. ovale to the skin of human volunteers under a nylon adhesive dressing with similarly negative results. The use of laboratory animals to simulate dandruff-like conditions has been rather limited. Martin-Scott (7) injected concentrated cell sus- pensions of P. ovale into mice and rabbits with no signs of pathogenicity and no evidence of antibody formation. Durfee and Cousins (8) were somewhat more successful in their attempts to produce dandruff with a P. ovale culture applied to the scarified skin of rabbits. These workers found that the induced infections were controlled with a number of antiseptic materials. Leone (9) was unable to produce a pathogenic re- action when P. ovale was inoculated into human and guinea pig skin. He concluded that P. ovale is a saprophyte of norxnal skin and that any increase in the pathogenicity of this organism is connected with an in- crease in the lipid content of the scalp. Spoor (10) also considers lipids to be important in the production of dandruff on animals and concludes that the high level of skin fat or sebum on humans provides an environ- ment for the initiation of dandruff.