BACKGROUND Allergy to Anisakis simplex (s.) is spreading due to the increased consumption of raw, smoked or marinated fish. In man, Anisakis s. can directly attack the gastrointestinal mucosa, provoking a parasitosis known as anisakiasis, or giving rise to the formation of IgE and, finally, inducing IgE-mediated reactions like urticaria, angioedema and anaphylactic shock. During recent years, a dietary approach to Anisakis s. infestation has also been addressed. METHODS A total of 620 patients with urticaria, angioedema, or both and a history of anaphylaxis following consumption of raw, smoked or marinated fish were recruited, evaluated for specific IgE levels to Anisakis s. and subjected to Skin Prick test. Following 18 month fish-free diet, patients were reevaluated at 6, 12 and 18 months, respectively. Patients undergoing diet were selected among those who had a clinical history with multiple accesses to first aid. RESULTS After 6-month fish-free diet, we recorded an improvement of symptoms and a remarkable reduction of specific IgE levels. The extension of the diet over 6 months in some cases resulted in a further reduction of specific IgE levels. CONCLUSIONS Data obtained confirm the importance of a fish-free diet in patients with severe symptoms since a new antigenic exposure coincides with a relapse of symptoms and increased IgE levels. This last point should be kept in mind and carefully evaluated in patients at risk for anaphylaxis or angioedema.