Anisakis simplex Hypersensitivity Is Associated with Chronic Urticaria in Endemic Areas

Background: Chronic urticaria (CU) may affect up to 1% of the general population. Anisakis simplex hypersensitivity is frequent in areas where raw fish is consumed and A. simplex allergy represents a relevant cause of acute urticaria. We assessed the possible association between CU and A. simplex sensitization in an area where marinated fish is very frequently eaten. Methods: A thorough history of CU was sought in 919 adults seen at the Allergy Center, Bari. CU patients and 187 controls underwent skin-prick testing with a commercial extract of A. simplex, and reactors were recommended a 6-month raw-fish-free diet regimen. Responders were followed after a further 3 months. Results: Of 919 subjects, 213 (23%) met the criteria for CU and 106/213 (49.7%) were sensitized to A. simplex with a significant difference between patients aged >65 or <65 years (56 vs. 41%, respectively; p < 0.05). All patients hypersensitive to A. simplex were regular consumers of marinated fish. In a control population without CU, the prevalence of A. simplex sensitization was 16% (p < 0.001). The 6-month diet regimen led to the disappearance of urticaria in 82/106 cases (77%) versus 1/42 (2%) subjects who did not change their dietary habits (p < 0.001). All nonresponders were sensitized to house-dust mites. Of 75 responders who were followed-up after 3 months, CU relapsed in 88% of those who had reintroduced raw fish versus 14% of those who were still on the diet (p < 0.001). Conclusion: In areas where raw or marinated fish is frequently eaten, A. simplex hypersensitivity is a frequent cause of CU.