THE INVESTIGATION OF DANDRUFF 615 sents data giving rise to non-periodic oscillation. There was a suggestion that dandruff might be subject to sudden exacerbations following undefined stimuli arising at random time-intervals. Qualitative observations also suggested, for example, that isolated spells of exceptional stress, either psychological, such as the sitting of examinations, or physical, e.g. acute respiratory infection, would result in sharp changes in the dandruff level. PATTERN OF CLINICAL OBSERVATIONS Our studies did not show that dandruff was seasonal, but whereas we hoped to express the level for an individual over a long time-interval in terms of the average, fluctuations about this average were not wholly random. The index of dandruff that we recorded was not entirely a measure of the rate of scale-formation there must have been an inter- relation between the generation of scales and their dispersal. Thus, for example, increased cementation of horny material would probably have tended to augment the score, as would any tendency to increased cellular activity. Another limitation was the frequency with which it was con- venient to record observations the true periodicity of changes in dandruff level may have been shorter than 6 weeks, but fluctuations of such frequency would have been lost completely with fortnightly examinations. It was, however, frequently noticeable that dandruff could increase sharply from a low level to a high level between two successive observations when this occurred, return to "normal" could be equally rapid or else spread over many weeks or months. This could imply that there were differences in the ceinentation of the scales or that an enhanced rate of generating scales might continue for variable lengths of time. General impressions arising from our investigation were that a high proportion of the population studied by us exhibited measurable levels of dandruff at all times and that, in the course of many hundreds of observations on numerous panels of subjects, no cases of long-lasting "spontaneous re- mission" were seen. MICROBIOLOGY OF DANDRUFF The observed course of dandruff might be explicable in terms of a microbial infection of low virulence. This could be due to the production of a toxic effect by a predominantly saprophytic organism if the host resistance is low. Alternatively, the organism may stimulate a delayed allergic reaction in the scalp tissues. Since a distinctive feature of the scalp is its abundant sebaceous activity, it has been tempting to consider a lipophilic organism as the possible causative agent. Among the in- habitants readily isolated from the human scalp is the yeast, Pityrosporum ovale. This micro-organism originally described by Rivolta (2) and more

616 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS fully by Malassez (3), was the subject of an extensive study by Martin- Scott (4), who characterized it as an asporogenous, non-mycelial yeast. He was able to culture P.ovale from 54.5% of normal scalps and 45.7% cases designated as exhibiting lesions of pityriasis capitis, but he failed to obtain positive cultures in 15 attempts on acute seborrhoeic dermatitis lesions his final conclusion was that P.ovale was a non-pathogenic saprophyte. However, since dandruff is clearly a disorder of low-grade pathogenicity and the culture of P. ovale is not at all easy by published methods, it seemed worthwhile to carry out further studies. One route by which an indication of the possible role of P.ovale might be studied would be to see whether dandruff was resolved when this organism was eliminated from the scalp. We therefore initiated a panel test accord- ing to our clinic routine with concurrent cultural studies and we tried to reduce the level of infection radically. This required an effective dis- 5nfection of the scalp along with a quantitative sampling routine and a !good recovery technique for P. ovale. Results were not as conclusive as -we had hoped owing to incomplete removal of organisms from the scalp, but our methods may help other investigators to pursue such studies further. Recovery of P.ovale Cultural requirements peculiar to P.ovale may be summarised thus :-- {i) An abundant oxygen supply is essential. {ii) The optimum temperature for rapid growth is 37øC. (iii) Satisfactory growth is achieved over the range pH 5 to 7. (iv) A moist atmosphere and freshly-prepared medium are desirable. (v) A fat source is necessary for prolific growth, preferably with a dis- persing (emulsifying) agent. (vi) Antibiotics such as Penicillin and Streptomycin are necessary to prevent bacterial overgrowth. This can be achieved at concentra- tions which do not inhibit P.ovale. (vii) Cycloheximide up to 250 •g/ml is useful for retarding the develop- ment of mould spores, though it does not significantly inhibit P.ovale at this dilution. In the course of prolonged efforts to yield a substrate capable of giving maximal recoveries and typical colony growth, the following medium has proved satisfactory :-- P.ovale Culture Medium (H. Dixon's Formula) Supplier Malt extract agar Oxoid CM59 6% Ox-bile desiccated Oxoid L50 2%