Lack of effect of cimetidine in chronic-idiopathic urticaria.

The effect of an H1 and an H2 receptor blocker singly and in combination was studied in 20 patients with chronic idiopathic urticaria. Both H1 receptor blockade alone and in combination with H2 receptor blockade produced a significant reduction in wealing and itch; there was no significant difference between these treatments. H2 blockade alone produced no significant reduction in wealing; there was a slight increase in itch, though not statistically significant.