Freezing protects against allergy to Anisakis simplex

Background: Allergic reactions to Anisakis simplex have been described foll owing ingestion of fish and were thought to be possible even if seafood is frozen or well-cooked. Objective: This Study aimed to confirm, by challenge test, that dead A. simplex larvae are not able to trigger allergic reactio ns in patients with proven hypersensitivity to this parasite. Methods: Simp le-blind, placebo-controlled, oral challenge tests with frozen A. simplex l arvae were performed in 12 patients who had suffered severe anaphylactic re actions after ingestion of seafood and diagnosed of A. simplex hypersensiti vity by skin prick test and specific IgE. If no reaction appeared, they wer e told to eat frozen seafood. 63 patients who had suffered urticaria or urt icaria/angioedema by demonstrated hypersensitivity to A. simplex were also advised to eat frozen seafood. All of them were reevaluated 6 months later. Results: All patients tolerated the dead larvae challenge test. After eati ng previously frozen seafood at least two times per week, all patients, inc luding those who had suffered anaphylactic reactions and those who had only presented cutaneous manifestations, remained asymptomatic. Conclusions: An isakis simplex-allergic patients tolerate ingestion of dead larvae. It is p robable that these patients can eat frozen fish and that a seafood-free die t is not necessary.