Attempts to mimic the repeated open application test in the guinea pig

The aim was to mimic the repeated open application test (ROAT) procedure, well established in humans, in an animal model. Guinea pigs were induced with cobalt chloride (CoCl2). They were then challenged by repeated open application (4 sites/animal) of various concentrations of the allergen in 10% DMSO 1 x a day for 7 days, to study dose dependency, morphology of test reactions and time course. The reactivity at the test sites to repeated open application was dose- and time-dependent. There was good agreement between the results of the treatments with CoCl2 and the post-treatment patch test results. Among 26 of the 29 animals, such agreement was found when 10% DMSO was used as vehicle. However, some reactivity was also observed in pretests at sites exposed to petrolatum. We suspect that this may be due to contamination and/or irritancy of the vehicle.