Background: Anisakis simplex is one of the nematode worms that parasitize sea mammals. When its larvae are accidentally ingested by humans, they can infect the host, resulting in anisakiasis manifested by digestive symptoms, or they may cause an allergic reaction, which in some cases may be severe.
Case reports: We report three cases of acute urticaria associated with abdominal pain, and hypotension in two of them, starting two to six hours after ingestion of raw fish. The diagnosis of an allergic reaction caused by Anisakis simplex was based on the clinical histories and positive tests for anisakis-specific IgE.
Discussion: In patients with acute urticaria associated with abdominal symptoms, a history of ingestion of raw fish in the preceeding hours is evocative of gastro-allergic anisakiasis. In association with symptomatic treatment, gastrointestinal endoscopy allows the larvae to be visualized and removed, which may relieve the symptoms and provide a diagnosis before the results of skin testing and serological assay are known.