SummaryOur bi-specialty clinic was established to systematically investigate patients with suspected peri-operative hypersensitivity reactions. Four hundred and ten patients were studied; 316 following an intra-operative reaction ('postoperative' group) and 94 with a previous history of reaction, referred before undergoing anaesthesia ('pre-operative' group). In the postoperative group, 173 (54.7%) were diagnosed with IgE-mediated reactions: 65 (37.6%) to neuromuscular blocking drugs; 54 (31.2%) antibiotics; 15 (8.7%) chlorhexidine and 12 (6.9%) patent blue dye. Reactions were severe in 114 patients (65.9%). All reactions to patent blue dye were severe. We identified IgE sensitisation in 22 (13.2%) cases with isolated mucocutaneous reactions. Only 173 (54.7%) patients had serum tryptase samples taken. Referrers' suspected causal agent was confirmed in only 37.2% of patients. Of 94 patients reviewed 'pre-operatively', 29 (30.8%) were diagnosed with IgE-mediated hypersensitivity reactions, reinforcing the importance of investigating this group of patients. Knowledge of the range of causative agents identified in our study should guide the investigation of suspected peri-operative hypersensitivity reactions.