Influence of the vehicle on elicitation of contact allergic reactions to acrylic compounds in the guinea pig.

Many factors can influence the elicitation of hypersensitivity reactions in guinea pigs and humans. The effect which the vehicle might have on the test response in guinea pigs sensitized with various acrylic compounds, using the "guinea pig maximization test", has been investigated. A marked decrease in the number of positive animals was seen when acetone was used as test vehicle, compared to petrolatum. The same result was seen with alcohol as vehicle, when neopentyl glycol diacrylate (NPGDA) was used as an acrylic monomer model. The patch test locations on the guinea pig flank, also affected the test response. Half of the animals did not react when challenged near the abdomen, compared to a test site near the back. By means of HPLC-analysis, the possible adsorption of the acrylic monomer to the aluminium chamber or filter paper disc, was analysed. Our findings did not indicate that adsorption occurs. A decrease in the amount of acrylic monomer in the chamber with increasing time, was noted. There was a marked difference in the monomer residue between solutions with (darkness) and without (daylight) inhibitor. The monomer decrease was also more affected by an aluminium surface than a glass or filter paper surface. Aluminium oxide probably enhances the polymerization process. The discrepancy between the test results in this study, when petrolatum and acetone were used as test vehicles, is due to a polymerization process of the acrylic compounds. Thus, the petrolatum vehicle probably prevents polymerization of the acrylic monomer.