Anisakis simplex-sensitized patients: should fish be excluded from their diet?

Background: Anisakis simplex (A.s.) allergy is an emerging disease. The thi rd-stage larvae of this nematode are a source of hidden allergens in fish. There are no clear guidelines concerning dietary restrictions for patients with serum-specific IgE to this parasite. Objective: To follow up the clinical data and immunological parameters of p atients sensitized to A.s. during 6 to 23 months. Methods: The clinical symptoms and serologic status of 17 patients with spe cific IgE and positive skin prick test results to A.s. were studied prospec tively. Six of these had anaphylaxis (ANA) attributed to A.s. and 11 patien ts experienced concomitant chronic urticaria (CU). All patients were advise d not to eat fish for 6 months. Results: Four patients from the ANA group excluded fish, and ANA did not re cur. Two other patients with ANA refused to exclude fish; one remained free of symptoms and the other experienced several urticarial episodes. During this 6-month period total IgE levels decreased in all six ANA patients; spe cific IgE for A.s, decreased in four patients and increased in two. Two pat ients from the CU group did not exclude fish, and symptoms persisted in the se two patients. Clinical improvement was observed in 78% of the patients w ith CU who excluded fish. Total and specific IgE levels decreased in all th e patients with CU. Conclusions: Because ANA symptoms are very severe, patients should always b e advised to exclude fish until specific food allergens are identified. How ever, in patients with CU and specific IgE to A.s., only the clinical respo nse to fish ingestion will determine the need for strict fish avoidance.