Rapid Symptom Resolution After Adjunctive Oral Colloidal Silicon Dioxide in a Non-anaphylactic Hazelnut Allergy Reaction: A Case Report

Acute food allergy reactions that do not fulfil the criteria for anaphylaxis are common in the emergency department and are managed symptomatically, principally with H1 antihistamines.No current recommendation addresses the allergen that remains unabsorbed in the gastrointestinal lumen at the time of presentation.We report a case of a 44-year-old man with childhood-onset hazelnut allergy who presented 30 minutes after inadvertently eating a packaged dessert containing hazelnut, with generalised urticaria, intense pruritus, nausea, vomiting and crampy abdominal pain.He was haemodynamically stable with no respiratory or laryngeal involvement and did not meet diagnostic criteria for anaphylaxis, so adrenaline was not given.Alongside standard care with an intravenous H1 antihistamine and intravenous fluids, a single 3 g oral dose of colloidal silicon dioxide (SiO 2 ), a non-absorbed silica-based enterosorbent, was administered.Fifty minutes later, his gastrointestinal symptoms had resolved and the urticaria was found fading.He was observed for eight hours, developed no biphasic reaction, and was discharged uneventfully.Adjunctive enterosorbent therapy was well tolerated and was followed by rapid improvement.Because an intravenous antihistamine was given concurrently and spontaneous resolution cannot be excluded, no causal role can be attributed to the enterosorbent.The case is reported to draw attention to a mechanistically plausible but untested adjunct, not to advocate its use.