Does aspartame cause allergic reactions?

Although a number of studies have explored the issue, there has been no scientifically demonstrated link between true allergies and aspartame. In double blind placebo-controlled studies with people who believed they developed allergic reactions after consuming aspartame, researchers found aspartame was no more likely than a placebo to cause allergic reactions. In one study published in the Journal of Allergy and Clinical Immunology, subjects who believed they were allergic to aspartame received up to 2,000 mg of aspartame (about 12 cans of diet soft drink). Not one of the subjects had an allergic reaction after receiving the aspartame.

Another study, also published in the Journal of Allergy and Clinical Immunology, tested 21 subjects who said they had experienced hives and/or swelling from consuming aspartame. In a controlled setting, subjects were given increasing doses of aspartame and a placebo on different study days. They were then monitored for hives or swelling. Four reactions occurred – two after aspartame was consumed and two after the placebo was consumed. Researchers concluded that aspartame was no more likely than a placebo to cause hives or swelling. In addition to the scientific evidence, the FDA has investigated all complaints since 1980, and has stated that there has been a gradual decrease in reports of adverse reactions to aspartame received over time.