130 JOURNAL OF TIiE SOCIETY OF COSMETIC CHEMISTS If one assumes that the microbial flora is the cause of certain dandruff problems, then why are these members of the flora found on one scalp and not on another ? One logical answer is that the nutritional environ- ment on some scalps is favorable for the growth of certain microorga- nisms. If the presence of a favorable nutritional environment of the scalp is related to the metabolism of these individuals, it can be hy- pothesized that the scalps of these persons are predisposed to dandruff- producing microbial attacks. These suggested metabolic factors are: hormonal inbalance imparied metabolism and nutrition dietary in- discretions, as excessive carbohydrate and lipid intake increased nervous tension and biochemical changes of the cutaneous scalp (11). Other metabolic factors reported by Spoor (49, .50) are: the condition of the epidermis which may be a function of the individual's genetic makeup, his sex, age, and race and the amount and quantity of the sebum pro- duction. It is felt that more work on the specific resident microbial flora of subjects known to have a dandruff condition should be conducted, particularly those which respond to treatment by antimicrobial agents. This would better establish a cause relationship between specific resident organisms and dandruff. More work should also be done on the rela- tionship of dandruff to one's metabolic activities. A second factor which makes it difficult to establish a causal relation- ship is that microorganisms are continuously being added to and removed from the scalp by numerous external agents such as combs, hands, rain, hats, air, and soot. This uncontrolled addition and removal of micro- organisms explains some of the variations in our work as well as the fluctuations in bacterial plate counts noted by VanderWyk and Roia (8) and by Van Buskirk (10). A third factor is that there is a substantial time interval between the appearance of an increased microbial flora and a measurable increase in the production of scurf. This lag was noted by VanderWyk and Roia (8) after the application of an antimicrobial mixture had been stopped. The immediate return of high bacterial counts of microorganisms on the scalp was not accompanied by a significant increase in scurf weight until three weeks later. Our work also indicates that a longer presampling period of perhaps two to three weeks is necessary in order to permit the scalp to reach a balance between the increase in microbial flora and scurf production. We believe that a more conclusive relationship between scurf production and microbial isolates could be shown if this procedure were carried out.

FLORA OF SCALP AND DANDRiJFI½ 131 Finally, it is conceivable that no specific microorganism is involved in scurf production, but rather dandruff is due to an increase in the entire resident microbial flora, with each member having similar nutritional requirements. SUMMARY 1. The nature of the resident microbial flora isolated fr'om the scalps of 28 college students with dandruff was compared to the resident flora isolated from 24 students without dandruff. The occurrence of dan- druff was determined visually, and by removing and weighing exfoliated dandruff flakes (scurf). 2. Studies included: a questionnaire survey of the prevalence of dandruff in 502 college students the isolation, identification, and prev- alency of the resident flora relationship of scalp pH to dandruff and relationship of resident flora to dandruff production. 3. A questionnaire survey of 502 students of college age indicated that 70.1% of them had a dandruff problem. 4. Four techniques of isolation of resident flora were used on the first six subjects. Best results were obtained using Noble Agar base method adjusted to the pH of the individual scalp and using scurf as the only source of nitrogen. This method was used to study the flora of the other 46 subjects. ,5. A total of 225 resident isolates was obtained by cultural methods. These included: 30 yeasts, 143 molds, 44 bacteria, and 8 actinomycetes. 6. The prevalency of Pityrosporum ovale and P. orbiculare was determined by direct smear observation. P. ovale was found in 96.4% of the subjects with dandruff and in 75.0% of the subjects without dan- druff. P. orbiculare occurred in 82.1% of the subjects with dandruff and in 70.8% of those without dandruff. P. orbiculare was always found less frequently than P. ovale on the same scalp. 7. The two most common resident yeasts isolated in culture were Rhodotorula mucilaginosa and Candida parapsilosis. Yeasts were found in 56.4% of the subjects with dandruff and in 29.2% of those without. 8. Resident molds were isolated from every subject regardless of scalp condition. The two most prevalent molds were Aspergillus awamori (98.1%) and A. fumigatus (80.7%). The average number of species of molds isolated from subjects with dandruff was 3.1, compared to 2.3 from subjects without dandruff. 9. Resident bacteria were found in 57.1% of subjects with dandruff and in 2,5.0% of those without dandruff. The most prevalent species