Sodium cromoglycate and provocation tests in chronic urticaria.

Twenty patients with chronic urticaria exacerbated by aspirin or tartrazine were challenged with the offending substance after pre-treatment with either oral sodium cromoglycate or placebo in a double-blind, crossover study. The sequential vascular response test (SVR) described by Fisherman and Cohen 1-4 was used to assess response to challenge. Eighteen patients were protected by oral sodium cromoglycate and one by placebo, taking as a positive response an increase in the bleeding time of 100% or more over control values.