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.
James Cook University researcher Dr Thimo Ruethers, who led the work, said fish allergies vary by region and may affect up to 3% of the population.
"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," said Dr Ruethers.
The team, headed by Prof. Andreas Lopata, focused on identifying allergens—proteins in fish that bind to human Immunoglobulin E (IgE) antibodies.
"If you have an allergy, your immune system overreacts by producing allergen-specific IgE antibodies in blood. Those antibodies sit on certain cells, which when exposed to fish proteins release substances, causing an allergic reaction," said Prof. Lopata.
He said while more than 1000 different fish species are consumed globally, knowledge about species-specific and fish-specific allergenicity remains limited.
Dr Ruethers said the team analysed 39 Malabar red snappers using protein separation, antibody assays and quantitative mass spectrometry to map allergen profiles across fish sizes, body regions and production origins.
"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," he said.
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 eleven registered fish allergens," Dr Ruethers said.
Prof. Lopata said 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.
"This study provides a blueprint for systematically assessing allergy risks. We suggest risk assessments and mitigation strategies should consider fish size and body region, alongside species and product type. In the long term, this helps clinicians and producers tailor advice and products to reduce risks and promote healthier diets," he summarised.
PAPER
Ruethers T, Sean A, Karnaneedi S, Chin R, Leeming MG, Nguyen V, Huerlimann R, Nugraha R, Bade P, Vij S, Shen X, Limviphuvadh V, Williamson NA, Domingos JA, Jerry DR, Maurer-Stroh S, Andiappan AK, Lopata 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.
The findings build on the team's previous research on allergy diagnosis, fish product labelling and management challenges, allergens in fish, canned fish, crocodile meat allergy, safe alternatives to fish, gummy shark for allergic kids, and evaluating food safety in sustainable alternative food sources.
