Dermal Sensitization Study in Hairless Guinea Pigs with Dinitrochlorobenzene and Ethyl Aminobenzoate

Abstract

This study was designed to investigate the use of adult female hairless guinea pigs, bred at Charles River Laboratories, Inc. (CRL-IAF(HA)BR), as a model for dermal sensitization studies. These animals are euthymic and hairless except for continuous hair growth at the nose and feet. A modified Magnusson and Kligman dermal sensitization procedure was used. One group of Hartley and one group of hairless female guinea pigs were induced with 20% ethyl aminobenzoate (benzocaine) or 0.5% dinitrochloro-benzene (DNCB). Animals were first challenged with 10% benzocaine or 0.5% DNCB. A second challenge was conducted using 5% benzocaine and 0.1% DNCB. Compared with the Hartley guinea pigs, the hairless guinea pigs were statistically significantly more sensitive to the irritating effects of the compounds (grossly and histologically). No statistically significant differences occurred between the strains in the incidence of sensitization to DNCB or benzocaine when corrected for baseline response. Advantages of the hairless guinea pigs included easier viewing of weak responses, fewer lesions due to the taping and shaving process, and fewer patches removed accidentally during the 24 hr exposure periods.