Effect of histamine H2-receptor antagonists on delayed hypersensitivity.

The delayed skin-test response to four antigens was assessed before and after 6 weeks' cimetidine therapy in patients with duodenal-ulcer disease. In the eight patients who received cimetidine there was a significant increase in both erythema and induration after six weeks' cimetidine therapy. In contrast, the intensity of delayed-hypersensitivity reactions at 6 weeks was not increased in eight control patients who did not receive cimetidine. These studies indicate that therapy with an H2-receptor antagonist may be associated with an augmentation of delayed hypersensitivity responses.