358 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS show a large increase in bacterial flora, while those who used soap with diaphene still have a low flora level. TOXICITY ?lcute Toxicity. Diaphene at a dosage of two grams per kilogram did not cause deaths when force fed to young adult mice as a 5 per cent suspension in corn oil. This is far less toxic than hexachlorophene U.S. P. which has a reported acute oral toxicity for mice of 0.187 gin. per kilogram. ?lnimal Skin Irritation. Young adult Swiss albino mice were topically treated daily for two weeks with a solution of soap containing 5 per cent diaphene. No epidermal damage was noted. The skin showed the same appearance as when treated with soap without the antiseptic. Six rabbits were prepared by shaving their backs. Applications of a 5 per cent soap solution containing 2 per cent diaphene were made daily for three weeks on three animals the other three animals were used for control with a 5 per cent solution containing no antiseptic. Each application was made so as to saturate the exposed area. At the conclusion of the test, there was no evidence of abrasion, lesion or trauma. Three rabbits were treated in one eye with a 5 per cent soap solution con- taining 2 per cent diaphene, and in the other eye with a control soap solu- tion containing no bacteriostat. No rinsing was made of the eyes in either case. In all cases, tests and controls, the eyes reddened for two days and were entirely clear after one week. Repeat Human Patch Tests. Ten human subjects were patch tested with a 5 per cent soap solution containing 2 per cent diaphene based on soap weight. The patch consisting of one-inch 4-ply gauze with a rubber dam backing was secured by tape to the upper arm. The patch, saturated with the test solution, was kept in contact for an overnight period. This pro- cedure was repeated ten times over a period of three weeks. Skin readings were taken the following morning after each patch application. Two weeks following the tenth patch a challenge or final patch was given. It was found that at no time was any skin reaction observed for the soap containing dia- phene outside of a slight erythema which is characteristic of soap and which was also found for the control soap without antiseptic. These results indi- cated that diaphene at a 2 per cent level in soap under the exaggerated testing conditions of the repeat insult human patch test shows no primary irritation and no sensitizing properties. The successful use of a composition consisting of 5,4'-dibromosalicylani- lide and 3,5,4'-tribromosalicylanilide in several leading commercial soaps for up to three years attests to the safety of the material. Also, a number of topical pharmaceuticals have been used for an equal period on over five hundred patients without any reported incidence of primary irritation or sensitization (9).

SAI,ICYLANILIDE COMPOSITION FOR SOAPS AND COSMETICS 359 APPLICATIONS A bacteriostat in soap, in order to be truly effective, should not only have a high degree of activity against microSrganisms found on the skin, but should also have a high degree of substantivity to the skin, so that subse- quent wear or washing will not remove the advantages of the protective antibacteiral mantel. Diaphene reacts with human keratin and other proteinaceous matter, such as wool and silk, and it can be exhausted quanti- tatively by immersing these materials in solution of the antiseptic. It has been observed that many very active antiseptics are readily removed from the skin surface and that the residual effect, if any, could be attributed to the inability of the researcher to remove the last vestiges of the antiseptic which were held predominantly by mechanical means. An effective soap bacteriostat must react with the proteinaceous com- ponents of the cutaneous surface in such a way that it is insolubilized at or near the skin surface and is thereby prevented from penetrating to sub- cutaneous levels where it may be absorbed and cause sensitization reactions. There appears to be a fine line between skin substantivity and skin sensiti- zation which is dependent in part upon the reactivity of the. bacteriostat toward amino acid residues. Because diaphene possesses outstanding antimicrobial activity, excellent substantivity to the skin, and a low order of toxicity, it is ideally suited for use in medicated or deodorant soap and detergent compositions. Further- more, the bacteriostat may be used in white soap tablets without producing discoloration. Concentrations of 0.3 to 0.5 per cent of diaphene are suflq- cient to reduce the bacterial flora of the skin, providing a protective mantel, so that the danger of secondary skin infections is reduced and the produc- tion of body odor by bacterial decomposition of perspiration is minimized. Diaphene is easily incorporated into bar soaps in the crutching operation. However, it is also possible to dispense the antimicrobial in the perfume if su•cient milling and plodding subsequently distribute the mixture uni- formly. Diaphene also possesses challenging potential as a cutaneous antimicro- bial for use in various topical pharmaceuticals, toilet preparations and medicated cosmetics. Its broad spectrum of activity against many cu- taneous pathogens, and its lack of toxicity are again of prime importance. Concentrations of 0.01 to 0.2 per cent are suitable for most cosmetic prep- arations. The limited solubility of diaphene presents certain formulation problems when clear aqueous or hydroalcoholic products are prepared. However, it is hoped that soon it will be possible to prepare such liquids by the use of new cosolvent and solubilizer systems which are currently under investigation. For example, 10 per cent diaphene can be solubilized in a solution of equal parts of triethanolamine, polyethylene glycol 400, and isopropyl alcohol.