180 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS In the rats, the skin area treated was about 9 X 2 cm, ,in the guinea pigs 10 X 3 cm. Approximately 10% of the body surface of the rabbits was covered. It should be mentioned that isopropyl myristate alone applied to the shaved skin of rabbits in daily doses of 0.5 ml/kg produced severe irritation single doses were without effect. Urine analysis was normal and failed to show any evidence of metabolic derangement or kidney damage after the application of hexachlorophene in isopropyl myristate or of isopropyl myristate alone. No changes in the hemoglobin or red blood' cell counts were noted there was a significant increase in the total white blood cell count of the rabbits which received 6 and 9 ml/kg. The results of these studies show that solutions of hexachlorophene are irritating to the shaved skins of experimental animals however, subsequent tests on human skin failed to show irritation. It will be noted that the damage to the skin of the animals was often severe enough to lead to absorption of the hexachlorophene and thus to systemic toxicity and even death. From a study (30) with radioactive hexachlorophene, it would appear that hexachlorophene is not absorbed to any significant degree when applied to the shaven, intact skin of rats. After several washings with a soap containing 2% hexachlorophene-C •4, smnples of fat and liver, believed to be the most likely sites of systemic accumulation, were taken from 7 rats after varying periods of time following washing. Samples of the dried tissues were burned to carbon dioxide which was precipitated as barium carbonate. The counts of this substance were identical with the background values showing that there was no radioactive hexachlorophene present in the tissues. Kehoe (31 ) made a study of the effects of hexachlorophene when put on the abdominal skin of rabbits over longer periods. Animals subjected to applications of a solution of hexachlorophene in dimethyl phthalate at a dosage of 75 mg/kg on 5 days weekly for 7 weeks exhibited slight retarda- tion in growth. There was moderately severe irritation of the skin no specific microscopic changes in the tissues were noted. When 20 mg/kg of hexachlorophene was applied for 18 weeks, the rabbits showed neither systemic reactions nor pathologic alteration of tissues induced by the absorp- tion of the compound. To determine the irritating and sensitizing properties of products for the human skin, various methods of patch testing were employed. The pro- cedure recommended by Schwartz et al. (32) was used by Traub et al. ($$) on about 600 subjects with 0.5 and 1% hexachlorophene in petrolatum. The particles were applied in the usual manner and the tests were read after 5 days. The results were all negative. To find out whether sensitivity

TOXICOLOGY OF HEXACHLOROPHENE 181 might have been produced, each patient was patch-tested again 10 days I _ •-___ All taLCS. z•n the tests were negative, indicating that hexachlorophene was non- irritating to the skin and was not a sensitizer. Similar negative results were obtained by Udinsky (34) with an 8r)•o solution of a bar soap containing 2% hexachlorophene Schwartz (35) also reported that a deodorant soap with 2 % hexachlorophene was not more irritating or sensitizing than ordinary soap. Furthermore, he stated that several million cakes of deodorant soap have been used by the public with no reports of proven cases of sensitization. In our opinion, the widespread use of a product over a long period of time is the best criterion of its safety and is more reliable than artificial methods of testing. Hexachlorophene is used in hundreds of products by a very large number of people in the United States and foreign countries, but remarkably few cases of irritation and allergy have been reported. Epstein (36) found two patients to be allergic to hexachlorophene, but stated that "hexachlorophene sensitivity is rare, and usually a consequence of sensitization to a chemically related and more potent antigen such as bithionol or tetrachlorosalicylanilide." References in the literature which attest to the fact that hexachlorophene is well tolerated by the human skin are too numerous to list here. It should suffice to repeat only Suskind's (37) statement: From the data of animal experiments (38) and "subsequent controlled human application one could conclude that hexachlorophene if used on the skin over long periods of time in nonirritating concentrations had little or no toxic potential. The experience of millions of users over the period of several years has demonstrated that this interpretation was correct." A single application of a patch was considered not to be a stringent enough test, and, for that reason, methods which would be more severe and perhaps resemble more the continuous use of a product were suggested by Shelanski and Shelanski (38) and by Draize (39). The so-called Repeated Insult procedure calls for repeated (10 to 15) applications instead of a single patch. At a time when these modified patch tests were introduced, soaps, emulsions, creams, etc., containing hexa- chlorophene had been widely used without bad effects. Nonetheless, addi- tional information is always of value and a few studies were made. The first one (40) was with a solution of hexachlorophene in 80% aqueous propylene glycol and with the solvent alone. Fifty subjects received 15 primary patches and a challenge application. Aqueous propylene glycol was found to have a mild irritant and fatiguing effect on the skin. More reactions (erythema) were noted with the hexachlorophene solution. No evidence of sensitization was seen in any of the subjects.