The effect of topically applied corticosteroid on irritant and allergic patch test reactions.

The purpose of the study was to assess the effect of topical corticosteroid on the patch test response in patients with known positive allergens and also to study any effect on the irritant response. In Study 1, 10 patients with known positive allergens had their backs pre-treated 2 x daily for 3 days with either betamethasone dipropionate 0.05% or the equivalent ointment base. On day 4, previous known allergens and dilutions of sodium lauryl sulfate (5% and 10%) as an irritant were applied to each side of the back. In Study 2 (4 patients), a 1:4 dilution of betamethasone dipropionate was substituted for the full-strength preparation. Betamethasone dipropionate 0.05% caused total or partial suppression of the allergic reaction in 8 of 10 cases. The 1:4 dilution caused partial suppression in 3 cases. The irritant reaction was totally suppressed by betamethasone dipropionate in 1 of 10 cases and partially suppressed in 7 of 10. The 1:4 dilution decreased the intensity of the irritant reaction in 3 of 4 cases. The relevance of these results to clinical practice is discussed.