Dietary assessment in five cases of allergic reactions due to gastroallergic anisakiasis

Background: Anisakis simplex can cause allergic reactions in sensitized patients. Some of these reactions are related to acute parasitism, as is shown in gastroallergic anisakiasis (anisakiasis with digestive and predominantly allergic symptoms). At present, a nonseafood diet is recommended for all patients with any kind of A. simplex allergy. We wished to confirm the clinical suspicion that patients with allergic symptoms after ingestion of raw or undercooked seafood who are sensitized to A. simplex, and diagnosed with gastroallergic anisakiasis, can tolerate the ingestion of seafood when the parasites are dead and noninfective. Methods: We included patients diagnosed with gastroallergic anisakiasis (positive skin prick test or/and serum specific IgE to A. simplex, with one or more parasites found by gastroscopy in the stomach). Patients included in the study gave written, informed consent. Specimens of A. simplex about 2 cm long were selected, placed in capsules, and frozen at -20 degrees C for more than 48 h to make them noninfective. We administered 11 specimens to every patient at the hospital. If they tolerated the larvae, they were told to eat well-frozen seafood (-20 degrees C at least 48 h). After 6 months, the patients were re-evaluated. Results: Five patients accepted the challenge with noninfective A. simplex larvae. All tolerated the noninfective larvae. After eating deep-frozen seafood for 6 months, no patient suffered a reaction. Conclusions: In gastroallergic anisakiasis, the antigens of the live parasite probably cause the allergic symptoms. Patients with this disease can tolerate deep-frozen seafood, in which the parasites are dead.