Fish allergy is a type of food allergy. Food allergy occurs when the body’s immune system wrongly identifies a food as a threat. When this happens, the body releases chemicals, such as histamine, in response. It is the release of these chemicals that causes symptoms.
Fish allergy refers to fish that have fins such as cod, plaice, haddock, herring, trout, salmon and tuna – as opposed to shellfish – and all types have the potential to cause allergic reactions. People who are allergic to one type of fish have a high chance of reacting to others as they contain similar proteins.
Allergy to fish often begins in childhood and may be lifelong. Some children outgrow their fish allergy but it’s not clear how likely this is to happen or at what age. Some research suggests it’s fairly common for children to outgrow their allergy in their teens. Fish allergy can also begin in adulthood.
The symptoms of fish allergy usually come on quickly, within minutes of eating the food.
Mild to moderate symptoms may include:
The term for this more serious reaction is anaphylaxis (pronounced anna-fill-axis).
Most healthcare professionals consider an allergic reaction to be anaphylaxis when it involves difficulty breathing or affects the heart rhythm or blood pressure. Any one or more of the ABC symptoms above may be present.
In extreme cases there could be a dramatic fall in blood pressure. The person may become weak and floppy and may have a sense of something terrible happening. Any of the ABC symptoms may lead to collapse and loss of consciousness and, on rare occasions, can be fatal.
AIRWAY - swelling in the throat, tongue or upper airways (tightening of the throat, hoarse voice, difficulty swallowing).
BREATHING - sudden onset wheezing, breathing difficulty, noisy breathing.
CIRCULATION - dizziness, feeling faint, sudden sleepiness, tiredness, confusion, pale clammy skin, loss of consciousness.
If you have an allergy to fish there is a chance you may have symptoms when you breathe in the vapours while fish is being cooked. This is because cooking causes the proteins that cause the allergic reactions to be released into the air. Fish proteins have also been found in the air in places where there is a lot of unpackaged fish, such as fish markets.
Not everyone with an allergy to fish reacts to breathing in fish proteins. It can be hard to know if you would have a reaction or how serious your symptoms would be. Make sure you discuss this with your allergy specialist.
Touching fish or fish products may cause skin irritation, itching or redness in some people with a fish allergy. Touching fish is unlikely to cause anaphylaxis. However, the risk of a reaction from touch could be increased if you have open cuts or wounds on your skin. Avoid touching fish and wash your hands thoroughly with soap and water if you do come into contact with fish.
If you work in the seafood industry, you are more at risk of developing an allergy to fish because you will be breathing in or touching fish proteins on a regular basis.
Symptoms include:
If you think you may be allergic to fish, see your GP who can refer you to a specialist allergy clinic if needed. They can find a clinic in your area from the British Society for Allergy and Clinical Immunology (BSACI).
It’s important to get a referral if your symptoms were serious. If symptoms are mild, then your GP may be able to arrange testing with a blood test to confirm the diagnosis.
If you get a referral, the consultant will discuss your medical history and symptoms with you. They might suggest skin prick tests, blood tests and, if needed, food challenge tests to help diagnose the allergy and work out how serious it may be.
Some clues that you might be at higher risk of more serious reactions are:
If you have asthma and it is not well controlled, this could make an allergic reaction worse. Make sure you discuss this with your GP or allergy specialist and take any prescribed medicines.
If you have mild allergic symptoms, you may be prescribed antihistamine medicine that you take by mouth. If you are at higher risk of anaphylaxis, you may be prescribed adrenaline to use in an emergency.
Adrenaline comes in pre-loaded adrenaline auto-injectors (AAIs) that are designed to be easy to use. Make sure you know how and when to use them. Ask your healthcare professional to show you how to use your specific brand of AAI. You can also find help and training videos on the manufacturer’s website and get a free trainer device to practise with.
You must carry two AAIs with you at all times, as you may need to use a second one if your symptoms don’t improve after five minutes or get worse.
The adrenaline auto-injectors prescribed in the UK are:
EpiPen®
EpiPen® is available in two doses: Adult: 0.3mgs of adrenaline Junior: 0.15 mgs of adrenaline (suitable for children weighing 5kgs – 25kgs / 1 stone 3lbs – 3 stone 13lbs)
Jext®
Jext® is available in two doses: Adult: 300 mcg of adrenaline Junior: 150 mcg of adrenaline (suitable for children weighing 15kgs – 30kgs / 4 – 4.5 stone)
Once you have been diagnosed with a fish allergy, you will probably be advised to avoid all fish (raw and cooked) and foods that contain it. This is because all fish contain similar proteins. There is also a high chance of cross-contamination, where one type of fish is contaminated with proteins from another. For example, in fish markets or supermarket counters where different types of fish are in close contact with each other.
Read the ingredient lists on food packets carefully every time you shop. Fish is included in the list of top 14 major food allergens in the UK. This means it must be highlighted on ingredients labels, in bold for example.
Read the ingredient list every time you buy a product as manufacturers change their recipes often.
Restaurants, cafes, hotels, takeaways and other catering businesses are required by law to provide information on major allergens, including fish. Ask staff directly if the food you’d like to buy contains fish and if there is a risk of cross-contamination. Let them know that even small quantities can cause an allergic reaction and don’t be afraid to ask staff to check with the chef.
Remember that everyday meals such as shepherd’s pie might contain fish as they sometimes contain Worcestershire sauce, which is made with anchovies.
If you are allergic to fish, you don’t have a higher risk of allergy to shellfish such as crustaceans (including shrimp, prawns, crayfish lobster and crab) and molluscs (including squid, octopus, scallops and oysters). This is because they contain different proteins.
Sometimes people are allergic to both, but this is probably a coincidence rather than cross-reactivity – where the proteins in one food are similar to the proteins in another.
If you see any of these on sale, check with staff to find out exactly what ingredients are used. The term ‘seafood’ could mean shellfish but it’s sometimes used to mean fish, so always check.
Fish gelatin is sometimes used in foods instead of beef or pork gelatin. It comes from the skin and bones of several types of fish such as cod, pollock, salmon and tuna. Some people who are allergic to fish are able to eat a small amount of fish gelatin, but it has been known to cause anaphylaxis. If you have a fish allergy, always check food labels carefully to see if the food contains fish gelatin. It’s sometimes used in marshmallow and nougat. Speak to your allergy specialist to check if it’s safe for you to eat fish gelatin.
It is not known if Omega 3 supplements made from fish can cause allergic reactions in people with fish allergy. If you’ve been advised to take an Omega 3 supplement, it’s best to use one made from a non-fish source to be safe.
Fish, or ingredients made from fish, can sometimes be found in cosmetics products:
It is not known how likely these products are to cause allergic reactions so it’s best to avoid them if you are allergic to fish. Cosmetics ingredients are written in Latin. Look on labels for the names ‘Pices’ or ‘Piscum’.
Some people who have allergic-type symptoms after eating fish may have one of these conditions, rather than a fish allergy:
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