Suspected tartrazine-induced acute urticaria/angioedema is only rarely reproducible by oral rechallenge.

Background: Tartrazine has been frequently linked to several diseases. However, a cause-and-effect role for tartrazine in these illnesses, especially in urticaria, has not always been established.

Objective: The aim of this study is to determine the incidence of intolerance to tartrazine among subjects who experienced an acute episode of urticaria/angioedema following the ingestion of a meal or a product containing this substance.

Methods: This was a retrospective study based on analysis of data of patients reported to have experienced episodes of urticaria and/or angioedema after ingesting meals or products containing tartrazine. At the first visit to the outpatients clinic, a careful anamnesis had been taken. Patients had then been submitted to the following diagnostic tests: IgE tests to common inhalant allergens and food allergens and a double-blind placebo-controlled challenge with tartrazine.

Results: A total of 102 subjects were enrolled in the study: 19 (18.6%) showed at least one relevant positive reaction to an IgE test for food allergy. Only one subject (1%) had reactions after ingestion of 5 mg of tartrazine, given on day 5. She did not have adverse reactions to placebo.

Conclusion: This study shows that the percentage of acute urticaria and/or angioedema induced by tartrazine is very low (1%). In view of our results, we suggest that all physicians with patients who have suffered adverse reactions that could be attributed to tartrazine should also carefully evaluate other possible causes.