Fish allergy (cod)
An itchy mouth after fish and chips, or hives after a fish soup? Cod is the reference allergen for fish, because its main protein is shared, in similar form, by many other fish. Our test checks for IgE antibodies to cod parvalbumin (Gad m 1), as part of 300 allergens and allergen components in the same sample.
- Group
- Food
- Also known as
- fish, Atlantic cod, Gadus morhua, parvalbumin, Gad m 1, bacalao
Where you meet it
- Cod, haddock, pollock and other white fish
- Fish fingers, fish and chips, fish cakes and fish pie
- Salt cod (bacalao, klippfisk) and stockfish
- Fish stock, fish sauce, Worcestershire sauce and Caesar dressing
- Cooking fumes where fish is fried or steamed
Parvalbumin: why one fish often means several
The main fish allergen is parvalbumin, a small muscle protein. In Atlantic cod it is called Gad m 1. Parvalbumins from different bony fish look similar, so many people sensitised to cod are also sensitised to other fish, such as haddock, salmon or herring.
Parvalbumin survives cooking well, so cooking does not usually remove it. The amount differs between species: white fish such as cod tend to have more than tuna or mackerel. That is a tendency, not a rule, and not a reason to try other fish without medical advice.
What people commonly report
Reactions people describe after fish include itching in the mouth, hives, swollen lips, vomiting and wheezing, usually within minutes to two hours. Some react to fish steam or to handling raw fish.
Swelling of the lips or throat, or trouble breathing, is an emergency. Call 112 (EU) or your local emergency number.
Fish is not shellfish, and not histamine
Shellfish such as shrimp have a different main allergen, tropomyosin. Sensitisation to fish does not imply sensitisation to shellfish, though some people have both.
Spoiled fish, especially tuna and mackerel, can build up histamine and cause flushing, headache and a rash that looks like an allergic reaction. This is called scombroid poisoning. It is not an allergy and does not show up as IgE.
How our test checks cod
The lab measures IgE to cod parvalbumin (Gad m 1), a single protein (molecular component). There is no whole cod extract on the panel. Other fish are on the panel too: salmon, herring, mackerel, tuna, carp, swordfish and thornback ray, most through their own parvalbumin. Your lab report gives it a measured value and class, from Negative to Very high. That shows sensitisation, which is not the same as a clinical allergy. Discuss the result with a doctor before changing your diet.
- Gad m 1: cod parvalbumin, the main cod allergen
- Does not measure: histamine reactions, IgG or food intolerance
Known cross-reactions
- Other bony fish
- Parvalbumins from cod, haddock, salmon, herring and other fish are similar. Sensitisation to several fish at once is common.
- Shrimp and shellfish
- Different main allergen (tropomyosin). Fish and shellfish sensitisation are separate, though they can occur together.
Sources
- EAACI Molecular Allergology User's Guide 2.0. Pediatric Allergy and Immunology, 2023.
- Seafood allergy: A comprehensive review of fish and shellfish allergens. Molecular Immunology, 2018.
Page last updated
300 allergens. One test.
A finger-prick sample at home, sent by post. A detailed lab report typically 5 days after the lab receives your sample, and our plain-English guide to reading it. €300, €1 per allergen.
Questions
If my result shows cod, does that cover all fish?
No single result covers all fish. Many people sensitised to cod are sensitised to other fish too, because of parvalbumin. A doctor or allergist can advise which fish, if any, you can eat.
Can I react to fish without eating it?
Some people report reactions to steam from cooking fish or to handling raw fish. If that happens to you, mention it to a doctor.
Is fish allergy the same as reacting to bad fish?
No. Spoiled fish can contain high histamine, which causes allergy-like symptoms in anyone. That is food poisoning, not an IgE allergy, and it does not show on this test.