A recent analysis of the European Anaphylaxis Registry has revealed that shellfish are an increasing cause of food-induced anaphylactic allergic reactions. The study was published in the Journal of Allergy and Clinical Immunology.

The European Anaphylaxis Registry collects standardized data on anaphylactic reactions from hospital-based allergy centers using an online questionnaire. The study included registry data reported from centers in 12 countries between the years 2007 and 2022.

A total of 462 cases of seafood-induced anaphylaxis were identified, equivalent to 8.8 percent of all food-induced anaphylaxis cases in the dataset. Of these cases, 316 (68 percent) were associated with shellfish allergens, and 146 (32 percent) were associated with fish allergens.

There were geographic and age differences in seafood-induced anaphylaxis. Shellfish was the cause most commonly in Italy and Spain. It was also more common in adults, causing 76 percent of cases. Fish allergies, however, were more common in children and adolescents (59 percent of cases).

Shrimp caused 76 percent of all shellfish reactions, while fish-induced anaphylaxis was attributed to cod (41 percent of cases), salmon (18 percent), and tuna (8.2) percent.

Shellfish reactions were more frequently related to larger portion sizes (48 percent of cases) and suspected cofactors (e.g., stress, exercise). In contrast, fish reactions were triggered by small amounts of allergen consumption.

Importantly, the data showed that shellfish-induced anaphylactic reactions are increasing among adults, because both the total number and the proportion among all cases of food-induced anaphylaxis have increased since the start of the registry in 2007. This trend may be linked to the global increase in shellfish consumption and/or the global increase in food allergy.