Perioperative anaphylaxis requires thorough explorations. When no active substance is detected as responsible for the anaphylaxis, investigations of potential responsible excipients should be performed.

We describe the case of a patient who experienced a perioperative anaphylactic reaction attributed to mannitol.

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A 15 year-old teenager was admitted to a tertiary care hospital for extraction of her wisdom teeth under general anaesthesia (GA). At the end of the surgery, she suffered from tachycardia, hypotension, bronchospasm and urticaria. She was immediately treated with epinephrine and transferred to the intensive care unit (ICU). One hour after the reaction, her tryptase level was 15.5μg/L, and it was 14μg/L two hours after. Her basal level of tryptase was 3.6μg/L. The patient was discharged from the ICU 24h later (total recovery) and was further referred to the allergy team for investigations. Drugs used during the GA were Rocuronium, Sufentanyl, Remifentanyl, Dexamethasone, Ketoprofen and Paracetamol. Skin pricks tests (SPT) and intradermal testing (IDT) at the recommended concentrations were performed for all drugs except for paracetamol (given orally in the ICU and well tolerated after the reaction). Skin testing was negative for all drugs, as were oral challenges (OC) for dexamethasone and ketoprofen. Serum specific IgE dosages for quaternary ammonium, latex, chlorhexidine were also negative. In absence of an obvious culprit, SPT and IDT for the intravenous form of paracetamol (containing mannitol) were performed. The SPT exhibited negative result, but the IDT of the pure dilution 10mg/ml and the 1/10 (1mg/ml) dilution were positive. It was then decided to perform SPT and IDT for mannitol 10% and 20%, at 1/100 and 1/10 dilutions, which turned out positive (but negative on 2 controls). An OC with an effervescent tablet of paracetamol (2000mg) containing mannitol was realised and was negative. Oral mannitol was well tolerated.

Our clinical case raises awareness about the possible allergy to mannitol when administered through the intravenous route even though the oral route is well tolerated.