Use of dose-response data to compare the skin sensitizing abilities of dicyclohexylmethane-4,4'-diisocyanate and picryl chloride in two animal species.

Groups of English smooth-haired guinea pigs and BALB/cBy mice were exposed to dicyclohexylmethane-4,4'-diisocyanate (HMDI) and picryl chloride (PiCl) by topical exposure. Guinea pigs were challenged 7 days later by patch testing and responses graded at 24 hr. Application of high doses of each chemical resulted in extensive erythema and a large proportion of animals became sensitized. Lower doses produced less sensitivity. In mice, sensitivity was assessed by extent of ear swelling upon challenge 5 days following the sensitization exposure. In mice, as well as in guinea pigs, a dose-response relationship was apparent between the sensitizing dose and both severity of response and number of animals responding. For mice, comparison of the dose of chemical required to sensitize 50% of the animals (SD50) yielded 0.40 mg/kg for PiCl and approximately 0.20 mg/kg for HMDI. Use of the SD50 should provide a method for assessing the ability of various chemicals to cause contact sensitivity.