As Food Allergy Week approaches in Australia, researchers are warning people with a taste for crocodile that it could trigger dangerous reactions if they are allergic to fish. 

Dr Thimo Ruethers, from James Cook University’s Australian Institute of Tropical Health and Medicine (AITHM) and Research Fellow in Human Health & Ageing at JCU’s Tropical Futures Institute (TFI) in Singapore, led the study. 

In collaboration with Dr Sam Mehr from The Children’s Hospital at Westmead, Sydney, and Epworth Hospital, Richmond, immunological reactions to crocodile meat were examined in 77 children who had immediate allergic reactions to fish. 

“Fish allergy affects up to 3 per cent of the general population and frequently results in life-threatening anaphylaxis. Crocodilians are known to be healthy and alternative protein sources, and alligator and crocodile meat is commonly eaten throughout the world and particularly across the tropics, where many crocodile farms are located,” said Dr Ruethers. 

However, he said recent reports of life-threatening anaphylaxis following the consumption of crocodile meat have been associated with a major fish allergen – a protein triggering a cascade of immunological responses which can result in an allergic reaction. 

Dr Ruethers and Professor Andreas Lopata, Professor in Molecular Allergy at the College of Public Health, Medical & Veterinary Sciences, AITHM and the TFI at JCU — in collaboration with a number of other researchers — set out to investigate this link. 

“Fish-allergic patients underwent allergen skin prick testing to crocodile and various types of fish. Skin reactions and comprehensive blood analyses then showed that the vast majority (about 70 per cent) of patients would likely have an allergic reaction when eating crocodile,” said Dr Ruethers. 

He said this is the first reptile allergen discovered, suggesting that crocodile meat can trigger allergic reactions in those allergic to fish. 

“We have now coined the term ‘fish-crocodile syndrome’: fish-allergic individuals may be at risk of serious allergic reactions upon consumption of crocodilian meat due to them being highly reactive to crocodile parvalbumin. This generally harmless protein is now the very first reptile allergen registered with the World Health Organisation.” 

Dr Mehr said fish-allergic individuals should avoid the consumption of alligator and crocodile meat unless tolerance is confirmed by medical means. 

More information in full paper (doi:10.1111/pai.13781), published in Pediatric Allergy and Immunology by Thimo Ruethers, Roni Nugraha, Aya C. Taki, Andrea O’Malley, Shaymaviswanathan Karnaneedi, Stephanie Zhang, A. Brenda Kapingidza, Sam Mehr, Sandip D. Kamath, Maksymilian Chruszcz, Graham Mackay, Dianne E. Campbell and Andreas L Lopata. 

Food Allergy Week in Australia is 22-28 May.

Background: 

The study is part of a larger project on fish allergies, funded by the National Health and Medical Research Council and supported through two PhD scholarships from the Centre for Food and Allergy Research, which will soon expand to become the National Allergy Centre of Excellence (NACE) based on recently announced federal funding. 

Discoveries include novel allergens in fish, safe alternatives to fish and challenges in diagnosing fish allergy and labelling fish products. 

One ongoing study at Epworth HealthCare, Melbourne, investigates if children with fish allergies can eat flake, funded in partnership between the Australian Food Allergy Foundation and Epworth Medical Foundation. 

Fish allergy is one of the most common food allergies worldwide among those that are not outgrown after childhood. Allergic reactions can be life-threatening and there is no cure for the serious, chronic immune disease. People suffering from fish allergy must often avoid all food potentially containing any fish as capacities for species-specific diagnostics are still limited.