Assay of topical corticosteroids. Efficacy of suppression of experimental Rhus dermatitis in humans.

Rhus dermatitis, experimentally induced in humans, was used as a model for determining the efficacy of various proprietary topical steroids. One-centimeter squares of vesicular dermatitis were induced by patch application of Rhus oleoresin. The steroids were then applied without occlusion once daily for four days, with readings of the therapeutic effect taken on the fifth day. Only potent steroids provided unequivocal suppression in this severe test. The rank order of efficacy corresponded to clinical experience. Cream and ointment formulations of the same steroid at the same strength did not differ. High strength preparations were more effective than regular strengths. Relief of pruritus was an important early effect of efficaceous steroids.