Acute urticaria and angio-oedema are common in primary care and in the emergency unit. Food allergy is one possible cause. We describe gastric anisakiasis, in which symptoms are often not obviously related to eating raw fish. A study was made of patients presenting at the emergency department who had allergic symptoms such as urticaria or angio-oedema and had recently eaten raw or undercooked fish. They were divided into two groups. Patients in group A (n = 13) also had abdominal symptoms and were diagnosed as having gastric anisakiasis by fibre-optic gastroscopy where third-stage larvae of Anisakis simplex were visualized and extracted. Skin prick tests and specific IgE to A. simplex were positive. Patients in group B (n = 13) had only allergic symptoms after eating raw fish. Eleven of 13 patients had positive skin prick tests and specific IgE to A. simplex. Three of 15 control subjects had positive skin prick tests and specific IgE to A. simplex. Allergic symptoms appeared from 2 to 20 h (mean 5.0) after ingestion in group A and from 20 min to 23 h (mean 4.3 h) in group B. Gastric symptoms in group A disappeared rapidly after extraction of the larvae. Allergic symptoms disappeared in most cases within the first 24 h. We suggest that the allergic symptoms in group A as well as in group B were mainly due to parasitization by A. simplex in sensitized patients. Gastric anisakiasis may be a widely underdiagnosed clinical entity.