A comparison of rabbit and human skin response to certain irritants

Abstract

The relative irritancy of 12 varying chemical structures was compared in man and rabbit utilizing a variation of the standard Draize rabbit irritancy test. Tests were performed on men's forearms, and 21-day occlusive and open tests were done on men's backs with techniques recently developed. The same scarification procedure was used in modifying the Draize irritancy test for man as that employed in rabbit testing. In the Draize rabbit irritancy test, Dibrom (dimethyl 1,2-dibromo-2,2-dichloroethyl phosphate), Hercules 9007 (a carbamate), formaldehyde and 0, 0-dimethyl-0,3,5,6-trichloro-2-pyridyl-phosphorothioate were moderate irritants. A similar test in man revealed only Dibrom and Hercules 9007 to have significant irritancy potential. The human 21-day occlusive testing showed these 2 compounds to be the severest irritants, but separated the irritancy potentials of the other compounds tested. In the 21-day open test only Dibrom was a significant irritant. Other chemicals tested included propylene glycol, undecenoic acid, sodium lauryl sulfate, diethyltoluamide, ethanol, a substituted acetamide and 2 other thiophosphoricacid derivatives. The Draize rabbit test accurately predicted the severe human skin irritants and nonirritants, but failed to separate the mild and moderate skin irritants. Several chemicals considered unsafe by the rabbit test proved nonirritating to human skin. When the rabbit testing was inconclusive, only human testing could separate mild and moderate irritants.