We report the case of a 4-year-old girl who presented to the emergency department after ingestion of a nickel-plated coin. Abdominal radiographs confirmed the presence of a coin in her stomach but she was otherwise asymptomatic. She was discharged with assurances that the foreign body would pass spontaneously. The patient developed significant generalised urticaria the next day, which became progressively more severe. Her symptoms prompted endoscopic removal of the nickel-plated coin and a postoperative course of corticosteroids and antihistamine therapy. This is the first reported case of generalised urticaria secondary to ingestion of a coin with nickel plating only (2% nickel content overall). A review of similar cases is provided.