63O JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS that an almost complete elimination of the microbial flora lessened the severity of dandruff by 31% in seven out of nine subjects studied. It is the purpose of this investigation to determine whether the bac- terial flora or the yeast flora has the greater influence upon scurf pro- duction. Included among the yeasts is Pityrosporum ovale, normally found in 80% of human scalps and considered by some to be dandruff- associated. It should be possible to control the nature of the scalp microbial flora by applying selectively acting antibiotics or mixtures of them to either side of the human scalp. Tetracycline* was used to control the bacteria and nystatinl to control yeasts. A mixture was applied when it was desired to suppress the entire microbial flora. Using the method of VanderWyk (9), scurf samples were removed with an Oster HairVac from both sides of the scalp prior to and during treat- ment. Quantitative comparisons based upon the weight of the samples indicated the severity of dandruff on both sides. METHOD Ten subjects were selected at random without consideration of their scalp condition. Each subject was given detailed instructions to follow throughout the entire experimental period. He was permitted to shampoo his head once with any nonmedicated product of his own choice one week before the start of the testing. Thereafter shampooing and swimming in chlorinated pools were not permitted. Sampling Periods The entire experiment lasted for 98 days and was divided into six sampling periods. Samples of scurf were removed and weighed on Monday, Wednesday, and Friday of each week. Pre-sampling Period: (7 days). During this time any special treat- ment of the scalp was discontinued, and each subject was permitted to apply only tap water to his scalp. No scurf samples were removed. Pre-treatment Period: (12 days). During this time the tap water treatment was continued, and samples of scurf were removed from both sides of the scalp three times weekly. This period established "nor- mal" scurf values for each subject. Treatment Period A: (26 days). Each subject was given two prep- * Tetracycline was supplied as Achromycin½ by Lederle Laboratories, a Div. of American Cyanamid Co., Pearl River, N.Y. I Nystatin was supplied as Mycostatin• by E. R. Squibb & Sons, Iq. ¾.

FLORA OF THE SCALP AND DANDRUFF PRODUCTION (531 arations, one to be applied on the right and the other to the left side of his scalp. One-half ounce of each was massaged into the appropriate side three times a day instead of the tap water which had been used during the pre-treatment period. tions are: Prep. LS-A (left side) Tetracycline 2.0 g Susp. P. ovale 1.0 ml Tap water 1000 ml The formulas for the two prepara- Prep. RS-A (right side) Tetracycline 2.0 g Nystatin 500,000 units Tap water 1000 ml The saline suspension of P. ovale organisms was obtained by isolating this yeast from the scalp of one of the subjects and was equal in density to that of a No. $ MacFarland nephelometer tube. The mixture of antibiotics applied on the right side of the scalp is inhibitory to both bacteria and yeasts, while Prep. LS-A used on the left side is inhibitory only to bacteria. During this period scurf samples were removed from both sides three times each week. Treatment Period B: (26 days). During this time the treatment on the right side of the scalp remained the same as in Period A. The formula for Prep. LS-B applied on the left side was: Prep. LS-B (left side) Nystatin 500,000 units Bacterial susp. 1 ml Tap water 1000 ml The bacterial suspension was prepared before the start of the experi- ment. Approximately $ mg of scurf from each subject was placed in 50 ml of thioglycolate broth. After incubation, the suspension o[ mixed bacterial flora was adjusted with saline to a turbidity equal to that of a No. $ MacFarland nephelometer tube. Prep. LS-B allows the bacterial flora to flourish in large numbers and at the same time inhibits the growth of P. ovale and other yeasts. Scurf samples were removed from both sides 3 times each week. Treatment Period C: (14 days). During this time the treatment on the right side of the scalp remained the same as before. Antibiotic treatment on the left was omitted entirely, and the preparation applied consisted of a mixture of suspensions of scurf bacteria and P. ovale prepared as previously described. The usual samples were removed three times weekly.