]. Soc. Cosine*. Chem., 22, 369-377 (May 27, 1971). The Accumulation and of Antibacterial Agents in Human Skin Persistence DAVID TABER, Ph.D.,* JOHN C. LAZANAS, Ph.D.,* OTIS E. FANCHER, Ph.D.,* and JOSEPH G. GALANDRA, M.D., Ph.D.* Synopsis--With the use of daily applications of a mixture of labeled HEXACHLOROPHENE and TRICLOCARBAN (3,4,4'-trichlorocarbanilide) in a soap vehicle, the accumulation and persistence of radioactivity on the dorsal surface of the hand were measured for five days. After the fourth application the amount remaining on the skin after rinsing seemed to ap- proach equilibrium. During any one day the amount of antibacterial ingredients decreased by 50%. The accumulation of antibacterial agents on the SKIN may explain the observation that the effect of ANTIBACTERIAL SOAP on the microflora of the skin is related to the number of exposures. INTRODUCTION It is a peculiarity of washing with antibacterial soaps or detergents that the antibacterial agents are deposited onto skin from vehicles whose function it is to remove substances from the skin surfaces. Although the mechanism whereby these agents are deposited is poorly understood (1, 2), the molecular structure of the deposited material (3-6) and the nature of the vehicle (7-9) are involved. Deposition of particles on skin is stated (10, 11) to be related to the psi and zeta potentials of the skin and the par- ticles. Several techniques have been used to measure the quantity of chemi- cals deposited on viable skin from different types of vehicles. Compeau * Research and Development Department, Armour-Dial, Inc., 3115 South Benson St., Chi- cago, Ill. 60608. *Industrial BIO-TEST Laboratories, Inc., 1810 Frontage Road, Northbrook, Ill. 60062, where investigation was conducted. 369

370 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (2) and Manowitz and Johnston (12) used organic solvents to extract anti- bacterial substances deposited on skin and analyzed the extracts spectro- photometrically. Fahlberg et al. (9) assayed the extracted agent micro- biologically. Investigating material deposited in particles large enough to be observed directly, Parran (13) stripped the skin with sticky tape and under magnification observed the amount of particles adhering to the tape. Shemano and Nickerson (14) and Stoughton (15) used radioactive hexachlorophene and measured the quantity sorbed onto the skin by sur- face counting. Using radioactive soaps, Hopf and Burmeister (16) ex- tracted the skin and examined the extracts for the amount of soap re- tained after washing. In the work reported here, which extrapolates the method of Shemano and Nickerson (14) to humans, the accumulation and persistence of a mixture of antibacterial substances deposited from soap onto human skin were studied. It is well known that antibacterial cleansing products such as hexachlorophene soaps or detergents exert their effect in a cumulative manner, the bacterial population decreasing with frequency of use until it is more or less stabilized at a level which is characteristic for each per- son (12, 17-20). Our work indicates that the amount of antibacterial agents on the skin approaches equilibrium. The composition employed in this study consisted of a soap solution containing a 1:1 mixture of hexachlorophene (2,2'-dihydroxy-3,3',5,5',6,6'- hexachlorodiphenylmethane) and triclocarban (TCC, 3,4,4'-trichlorocar- banilide), * the former compound being C-14 labeled in the methylene group and the latter C-14 labeled in the carbonyl group. A 1:1 combina- tion of hexachlorophene and triclocarban is found in a widely used anti- bacterial-deodorant soap. METHODS The experimental work included both animal and human studies. Albino rats were used to establish a relationship between skin surface counts and absolute radioactivity present in and on the skin. It was as- stimed that this relationship also would apply to the human studies. Two male and two female albino rats weighing 250 to 300 g were em- ployed. An area on the back (approximately 6 in. a) was closely clipped and depilated* to effect complete removal of hair. Chemicals were weighed to the nearest 0.1 mg and transferred quan- titatively to a 2% soap solution the formulations were homogenized in a * Active ingredients in Dial© soap, Armour-DiM, Inc., Chicago, Ill. t Nair, Carter Products, Inc., Ncw York, N.Y.