ANTIMICROBIAL EFFECT OF ZPT 33 6.0 5.0 1.0%ZPT ß I 2 3 4 Week • Control --• •-Tre a t • •-Control -• Figure 3b. Effect of non-medicated shampooing for ! week on the corneocyte count of the scalp, where dandruff suppression has been induced by ZPT. amounts of dandruff (Figures 4a & 4b) despite the continuedly significant suppression of Pityrosporum ovale (Figure 5). In this experiment, an apparent effect on aerobic and anaerobic bacteria was hardly demonstrated although a slight increase in their numbers occurred through 6 days of no shampooing. DISCUSSION The question of microbial involvement in the antidandruff mechanism of ZPT still remains to be further clarified. Thus, since Malassez (! 1) pointed out Pityrosporum ovale as chief suspect in dandruff etiology, there have been a large number of reports trying to confirm the link between the two. Most investigators (2,10,12-14) have concluded that there is no connection. However, these studies have not included microbiological analysis following ZPT treatments. Since ZPT is known to be a unique antidandruff agent available in the cosmetic field (15) which has a wide range of antibacterial and antifungal properties (5-8), it ought to be utilized for quantitative analysis with respect to the question of microbial involvement in the antidandruff mechanism. These factors led us to investigate relationship between microorganisms and dandruff in variety of ZPT application system. Our microbial studies demonstrated the following: 1) the only noteworthy difference in the microorganisms which occurs corresponding to the reduction of dandruff is the

34 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Dandruff Itching ß ß ß WO SO i I I I I i 0 3 4 5 6 7 Day Figure 4a. Effect ooe no shampooing for six successive days on dandruff suppressed by ZPT, as expressed by clinical grade and itching. 6.0 5.0 P*•O.001 i 7 Day Figure 4b. Effect of no shampooing for six successive days on dandruff suppressed by ZPT, as expressed by corneocyte count.