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

376 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS containing radioactive hexachlorophene, Stoughton (15) found that only 0.5% of the hexachlorophene applied to the skin remained one day after application, unlike the 50% of the mixture of agents found by us. A major difference between the two experiments, aside from the fact that we used soap, not detergent, as the vehicle, and a mixture of antibacterial agents rather than hexachlorophene, is that Stoughton washed the test site with plain soap and water immediately after applying the detergent, a procedure which can be assumed to remove a considerable portion of the deposited chemical. Diminution of the amount of antibacterials with time probably is due to a gTeat extent to normal shedding, turnover of the statum corneum, and, to a lesser extent, penetration (21). At the end of our experiment, application sites were stripped with cellophane tape followed by two washings with soap and water. Two such treatments failed to remove all of the radioactivity from the skin, but about 64 hours later skin surface counts had reverted to backgTound level. The accumulation of bacteriostats in skin may explain the observation (12, 17) that the effect of antibacterial soap or detergent on the micro- flora of the skin is related to the number of exposures to the product. Our data suggest that an antibacterial bar soap may be most effective if used regularly to allow maximum buildup of bacteriostatic film on the skin. (Received December 9, 1970) REFERENCES (1) Goldemberg, R. I,., Keratin substantivity, Drug Cosmet. Ind., 85, 618 (1959). (2) Compeau, G. M., The adsorption of dodecylbenzencsulfonate and hexachlorophene on the skin, ]. Amer. Pharm. Ass., Sci. Ed., 49, 574 (1960). (3) McNamara, T. F., Steinbach, M. L., and Schwartz, B. S., Skin substanli•i•y in the evalua- tion of antimicrobials, ]. Soc. Cosmet. Chem., 16, 499 (1965). (4) Taber, D., Yackovich, F., and Brown, J., Jr., The microbiological availability of soap bacteriostats, ]. Amer. Oil Chem. Soc., 44, 473 (1966). (5) McNamara, T. F., and Steinbach, M., In vitro evaluation of the tissue substantivity of selected antibacterial agents, Ibid., 44, 478 (1966). (6) McNamara, T. F., Skin substantivity. Some biological and chemical considerations, CSMA Proc., 53, 145 (1967). (7) Panzarella, F. P., and Dexter, 1). D., Germicidal liquid skin soap, Soap Chem. Spec., 37, No. 12, 73 (1961). (8) Gibson, J. w., Comparative antibacterial activity of hexacblorophene in different formu- lations used for skin disinfection, J. Clin. Pathoh, 22, 90 (1969). (9) Fahlberg, W. J., Swan, J. c., and Seastone, C. V., Studies on retention of hexachloro- phene (G-I i) in human skin, ]. Bacteriol., 56, 323 (1948).