Of the 63 patients that had testing, 47 (74.6%) were de-labelled, 13 (20.6%) had confirmation of a specific drug allergy, but showed tolerance to suitable alternatives (eg, cefazolin allergy but tolerance to cephalexin; diclofenac allergy but tolerance to aspirin), and 3 (4.8%) had positive outcomes: 1 with positive intradermal test to trimethoprim/sulfamethoxazole without further challenge, and the other 2 with a positive response to an alternate NSAID, suggesting cyclooxygenase-1 mediated hypersensitivity. This evidence concerns the gene PTGS1 and allergic disease.