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Fish allergies vary by region and may affect up to 3% of the population.

A new study reveals allergy risks from fish depend not just on species but also on the size of the fish and which part you eat.

With increasing frequency, the consumption of fish or fish products triggers severe allergic reactions. This form of allergy is associated with a higher probability of life-threatening anaphylactic shock than many other food allergies. Even skin contact with fish or accidentally inhaling fish fumes can trigger an allergic reaction.

If you have an allergy, your immune system overreacts by producing allergen-specific IgE antibodies in your blood. Those antibodies sit on certain cells, which when exposed to fish proteins release substances, causing an allergic reaction.

While more than 1,000 different fish species are consumed globally, knowledge about species–specific and fish-specific allergenicity remains limited. 

Research Results showed protein profiles varied markedly by fish size and muscle region, but not between farmed or wild-caught fish. Smaller fish contained higher amounts of the major allergens parvalbumin and creatine kinase, while larger specimens had elevated levels of heat-labile allergens.

Allergen distribution also differed across body regions, suggesting that various cuts of the same fish may pose different risks for allergic consumers. For example, the head region contained more than twice the amount of the major fish allergen compared to the tail.

However, differences linked to production origin—e.g., whether the fish were wild-caught or farmed—were minimal, affecting only two of the 11 registered fish allergens.

 Fish allergy is highly complex and many people allergic to fish react to multiple allergens, so the scientists could not recommend eating smaller or larger fish as a safer option.

Thimo Ruethers et al, Fish size matters – Variable food allergen profiles in farmed and wild Malabar red snapper (Lutjanus malabaricus), Food Chemistry (2026). DOI: 10.1016/j.foodchem.2026.147950