Aspirin sensitivity: acetylsalicylate or excipients

We present three patients who developed urticaria while taking an enteric formulation of aspirin, confirmed on a second exposure. Although hypersensitivity reactions to aspirin, especially in asthmatic patients or those with nasal polyps, are well reported, our patients did not exhibit any underlying history of atopy. Furthermore, two of the patients were able to tolerate a soluble formulation. We review the literature and discuss whether these symptoms might be caused by pharmaceutical excipients, present in very small amounts in the enteric coating, rather than the active ingredient acetylsalicylate. Adverse reactions to excipients are fortunately rare but are occasionally reported.