Applicability of Evans Blue Diffusion for Predicting Eye and Skin Irritancy to Chemicals in the Rat
Agents with known ocular and dermal irritant potential to humans, rabbits or guinea pigs were applied to the eye and skin of male rats. The degree of external ocular inflammation as well as skin injury was assessed by the quantification of the indicator dye extravasated in the upper eyelid and exposed skin area, respectively.
1-hour ocular exposure to the test materials increased the eyelid content of Evans blue consistently. Each agent which qualified as an eye irritant to other species also proved to be irritant to the eye mucosa of the rat. The amount of dye found depended on the agents or concentrations used or both.
2 to 4 h epicutaneous exposure was accomplished under total occlusion. A group of registered irritants (formaldehyde, cyclopentanon, solvents) caused pronounced dye accumulation proving their skin penetrability and cytotoxic potential, while other test materials with known skin irritancy in rabbits (e. g. certain detergents) failed to produce any dye accumulation in rats, probably, because of the poor cutaneous penetrability of these agents.
The dye diffusion technique adapted to the rat eye seems to be a sensitive and reliable screening method for predicting ocular mucosal irritancy to chemicals. Adapted to the rat skin, the test may be useful for screening skin penetrability and skin cytotoxicity of materials.