Single NSAID-induced reactions are immunoglobulin E (IgE)-mediated (true allergy or selective hypersensitivity), whereas the other types are mediated by cyclooxygenase-1 (COX-1) inhibition and are associated with cross-reactivity to multiple NSAIDs, including aspirin referred to as pseudo-allergy or cross-reactive hypersensitivity (6, 7). This evidence concerns the gene PTGS1 and Allergy.