Anisakis hypersensitivity in Italy: prevalence and clinical features: a multicenter study

Background: Anisakis simplex (As), a parasite in fish, is able to sensitize humans via the alimentary tract. The prevalence of hypersensitivity and allergy to As outside the Iberian peninsula has not been investigated so far. We investigated Anisakis hypersensitivity in different areas of Italy. Methods: Consecutive subjects seen at 34 Italian allergy centers from October to December 2010 were investigated both by specific interview and by skin prick test (SPT) with As extract. Results: A total of 10 570 subjects were screened, of which 474 (4.5%) scored positive on Anisakis SPT and 66 of these (14% of those sensitized; 0.6% of the studied population) had a history of As allergy. Marinated anchovies were the most frequent cause of allergic reactions. Thirty-four (52%) patients were mono-sensitized to Anisakis. Sensitization rate showed marked geographic differences (range: 0.4-12.7%), being highest along the Adriatic and Tyrrhenian coasts, where homemade marinated anchovies are an age-old tradition. In inland centers in northern Italy, the prevalence was directly related to the number of inhabitants. The analysis of the impact of immigration on the prevalence of Anisakis hypersensitivity showed that about 60% of sensitized subjects in Milano and Torino came from southern Italy or from non-European countries. Conclusions: Anisakis hypersensitivity and allergy are mainly a matter of dietary habits. Areas where marinated anchovies are popular can be considered as 'endemic' for this type of food allergy, whereas immigration and, possibly, new or imported trendy food styles, such as eating raw fish carpaccios or sushi, are a major causative factor in big cities of inland zones.