Aspartame is no more likely than placebo to cause urticaria/angioedema: Results of a multicenter, randomized, double-blind, placebo-controlled, crossover study

Background: Anecdotes and single case reports have suggested that the high-intensity sweetener, aspartame, may be associated with allergic/hypersensitivity-type reactions. Methods: We conducted a multicenter, placebo-controlled clinical study to evaluate individuals who had experienced urticaria and/or angioedema allegedly associated with ingestion of an aspartame-containing product. Despite extensive recruiting efforts over 4 years, only 21 subjects could be enrolled. After admission to clinical research units, subjects were given aspartame and placebo in a randomized, double-blind, crossover fashion. Subjects received, on different days, increasing doses (50, 300, 600 mg) of aspartame and placebo at 8:00 am, 10:00 am, and noon. Subjects who weighed less than 40 kg received one half of these doses. Conversion products of aspartame, aspartylphenylalanine diketopiperazine and β-aspartame, were also included in the aspartame arm of the study. Positive reactions were defined as urticaria (hives with wheals 4 mm or more in diameter with a collective diameter of at least 15 mm or one or more hives with a wheal of 4 mm or greater with a flare of 8 mm or greater) or as angioedema. Results: According to these criteria, four reactions were observed; two followed aspartame ingestion and two followed placebo ingestion (p = 1.00). The incidence of other adverse experiences was no different after aspartame versus placebo ingestion (p = 0.289). Conclusion: These results indicate that aspartame and its conversion products are no more likely than placebo to cause urticaria and/or angioedema reactions in subjects with a history consistent with hypersensitivity to aspartame.