Effects of vehicles and elicitation concentration in contact dermatitis testing. I. Experimental contact sensitization in humans.

A study was made to evaluate the effects of vehicle and challenge concentration on response of human subjects to potential allergens. In the vehicle studies the modified Draize test was used to test the response of subjects to cinnamic aldehyde and to costus oil, administered at two skin sites, in petrolatum and in 95% ethyl alcohol. In two tests of costus oil, alcohol proved to be more effective in eliciting a response than petrolatum; on the other hand, in one test with cinnamic aldehyde, no difference in results was obtained with these two vehicles. In the concentration studies, subjects known to be sensitive to the test substance were tested by the Al test with costus oil (three concentrations), chloracetamide (four concentrations), or thimerosal (three concentrations); petrolatum was used as the vehicle in each case. Results of the vehicle test showed no compelling reason for the selection of one vehicle rather than another. Results of the concentration tests indicated that concentration does have an effect on the intensity and frequency of reactions to potential allergens.