A 45 year old man presented to the emergency department with a suspected “allergic reaction”. He described facial and neck swelling, progressive inspiratory difficulty and pain on swallowing during the previous seven hours. On further questioning he said that swelling had begun one hour after a prolonged dental extraction for a right lower molar tooth abscess. The procedure had entailed several local anaesthetic injections and the use of an air turbine drill. After the procedure he had started a course of oral penicillin V. …