Anisakis simplex is a fish parasite that is a public health risk to those consuming raw or poorly cooked marine fish and cephalopods because of the possibility of becoming infested with live larvae. In humans, penetration of the larvae into the gastrointestinal track can cause acute and chronic symptoms and allergic anisakiasis. Excretion and secretion products released by the larvae are thought to play a role in migration through the tissues and induce an immunoglobulin E-mediated immune response. The aim of this preliminary study was to detect parasite antigens and allergens in fish tissues surrounding the migrating larvae. Hake and anchovy fillets were artificially parasitized with Anisakis larvae and stored in chilled conditions for 5 days. Larvae were evaluated for fluorescence, fish muscle tissue was examined with transmission electron microscopy, and immunohistochemical reactions of two rabbit polyclonal antisera against a parasite crude extract and the allergen Ani s 4 were recorded. Larvae immediately migrated into the fish muscle, and no emission of bluish fluorescence was observed. Fish muscle areas in contact with the parasite showed disruptions in the structure and inclusion of granules within sarcomeres. Both parasite antigens and the Ani s 4 allergen were located in areas close to the larvae and where sarcomere structure was preserved. These findings indicate that parasite antigens and allergens are dispersed into the muscle and might cause allergic symptoms such as dyspnea, vomiting, diarrhea, urticaria, angioedema, or anaphylaxis in some individuals sensitive to A. simplex.