Background Sodium benzoate (E 211) is widely used to delay yeast spoilage of acidic foods and beverages. Numerous cases of adverse reactions to benzoate have been recorded, but most of the studies that have been conducted lacked proper placebo controls or blinding.
Objective The aim of this study is to determine the incidence of intolerance to sodium benzoate among subjects who experienced repeated episodes of acute urticaria/angio-oedema following the ingestion of a meal or a product containing this substance.
Methods This was a retrospective study based on the analysis of data from patients reported to have experienced episodes of urticaria, with or without angio-oedema, after ingesting meals or products containing sodium benzoate. At the first visit to the outpatients clinic, a careful history was taken. Patients were then given the following diagnostic tests: tests for IgE for common inhalant allergens and food allergens, and a double-blind, placebo-controlled challenge with sodium benzoate.
Results A total of 47 subjects were enrolled in the study; five (11%) showed at least one relevant positive reaction to an IgE test for food allergy. Only one subject (2%) had a reaction after the ingestion of 75 mg of sodium benzoate without an adverse reaction to placebo.
Conclusion This study shows that the percentage of repeated episodes of acute urticaria/angio-oedema reactions induced by sodium benzoate is very low (2%). In view of our results, we suggest that when faced with patients who have suffered adverse reactions that could be attributed to sodium benzoate, physicians should also carefully evaluate other possible causes.