Does aspartame cause allergic reactions?

No. The overwhelming body of scientific evidence clearly demonstrates that aspartame, even in amounts many times what people typically consume, is safe and not associated with adverse health effects, including allergic reactions.

Studies investigating aspartame as a potential allergen have found no association between aspartame and allergic reactions. 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 placebo to cause allergic reactions.