374 JOURNAL OF THE SOCIETY OF COSMET1C CHEMISTS Table II Counting Efficiency •c/cm 2 in and on Skin Surface Counts % Efficiency 0.0202 7,500 3.65 0.0320 15,000 4.63 0.0565 30,000 5.25 Mean 4.51 Use of this value and others calculated similarly for different levels of total radioactivity gave the results shown in Table II. Persistence and Accumulation of Bacteriostats on the Shin From Fig. 1, the surface counts for male and female subjects and for the composite groups taken four times each day for a 5-day period were converted to microcuries of total radioactivity in and on the skin. Since there were no significant differences between male and female subjects, only the composite data are presented (Table III). These data are shown graphically in Fig. 2. Analysis of variance shows the differences between days and time periods within any day to be significant (p 0.0l). Table I I I Accumulation and Persistence of Labeled Germicides on Human Skin After Repeated Daily Applicationsa (Mean Values for Five Male and Five Female Subjects) Time of Increase Determination After 5 Post-Dosing Day I Day 2 Day 3 Day 4 Day 5 Days Immediate 25.0 b 28.0 29.4 30.8 32.3 7.3 15 Minutes 25.0 28.4 31.3 33.3 32.3 7.3 4 Hours 22.2 24.1 26.2 27.0 27.3 5.1 24 Hours 11.7 14.3 15.4 15.4 ... 3.7 Read across for accumulation and down for persistence. All values are given in •uc X 10a/cm 2 of skin. DISCUSSION Inspection of Table III indicates an apparent gradual leveling out of the amount of sorbed material by day 4, the values for that day being about 25% greater than on day 1. It is likely that this represents equilib- rium conditions related to the quantity of antibacterial agents applied per unit area of skin. Of interest is the decrease of activity during any

ANTIBACTERIAL AGENTS IN HUMAN SKIN 375 one day: 24 hours after application the amount of agent present de- creases by 50%. Our results differ from those of Compeau (2), who found no difference between the amount of hexachlorophene extractable from skin immediately after scrubbing the hands with an antibacterial de- tergent or after using the product exclusively for five days, but are in agreement with those of Manowitz and Johnston (12), who measured the hexachlorophene extractable from the entire forearm. Using a detergent 0 Immediate A 15 minutes [] 4 hours $ 24 hours 1 2 3 4 5 Test Day Figure 2. Relationship between number of applications to humans of soap solution contain- ing labeled hexachlorophene and triclocarban and the radioactive content of skin