Immediate and cell-mediated reactions in parasitic infections by Anisakis simplex.

BACKGROUND Anisakis simplex is responsible for allergic symptoms after repeated ingestion or contact with parasitized fish. OBJECTIVE To further analyze type I and IV immunologic mechanisms in a group of patients with allergic reactions to A simplex, we performed prick-by-prick testing with A simplex larvae and patch tests with live, cooked, or frozen larvae of the A simplex parasite. METHODS Thirty-eight patients underwent skin prick test and radioallergosorbent test with inhalant allergens, foods, and A simplex. Prick-by-prick tests with A simplex and patch tests with live, cooked, and frozen larvae were carried out in 10 patients with evidence of allergy to A simplex. RESULTS Prick-by-prick testing yielded a positive result in 100% of cases with live larvae and in 70% with cooked and frozen larvae. Patch tests with A simplex were positive in 8 patients for live larvae, in 3 patients for frozen larvae, and in 1 patient for cooked larvae. CONCLUSION Our data emphasize that A simplex is responsible for both immediate allergic reactions and cell-mediated (delayed) reactions, in particular in subjects with occupational exposure. In addition, our data demonstrate that not only live but also frozen and cooked larvae can induce sensitization. This observation may be explained by differences in the allergenic proteins involved, and further studies will be required to address this possibility.