Fish allergy is amongst the top seven food allergies in children.
Symptoms can occur not only after eating fish, but also after contact or from breathing the fish vapour during cooking or at a fish market. Usually only a hives or “nettle” rash develops after contact with fish. Sometimes as well as a rash, swelling, especially around the face may occur. Some children have an itchy throat; others vomit or can have diarrhoea. Severe reactions are much less common, but can include difficulty in breathing (with wheeze or swelling in the throat) and feeling faint or dizzy. Vapours from the fish may trigger an asthma attack in children that are allergic.
Allergy to fish should not be confused with Scromboid poisoning. This is a type of food poisoning from eating fish that is not stored correctly. It is more common in warmer countries than in the UK. A chemical (histamine) builds up in the fish as
it decomposes and remains even after cooking. Sometimes the fish has a metallic or peppery taste. The symptoms are often the same as an allergic reaction.
Most people with fish allergy only have mild reactions. Severe reactions affecting the child’s breathing can occur, particularly in those with bad asthma and these need urgent medical attention.
People who are fish allergic may be able to eat shellfish. Some people are just allergic to white fish such as cod and haddock but can tolerate salmon and tuna. People allergic to fish need to be aware of the risk of cross-contamination in restaurants, markets and open fish counters.
The diagnosis of fish allergy is based on the history of a typical reaction after contact with fish. Positive allergy tests skin prick or blood IgE tests support the diagnosis, but should not be used alone, as people can have positive allergy tests but tolerate the fish without getting a reaction. Skin prick tests are safe and can be done in clinic, provided that the child has not had any antihistamines for a few days. Blood tests are not affected by antihistamines, but the results are only available in a week or so
after the clinic appointment. If the diagnosis is uncertain an oral fish challenge is sometimes recommended.
Fish is easy to avoid. One should be careful of cross contamination when buying fresh fish in shops and supermarket counters. Food fried in oil that has also been used to fry fish will be contaminated. Some foods and dishes like paella, bouillabaisse, gumbo and frito misto may contain fish and should be avoided, as should some thai curries which can include fish sauce. Your doctor will advise your child whether they should avoid all fish or just need to avoid white fish and can eat salmon and tuna or both. Most patients that are allergic to white fish can eat shell fish.
Anisakis (round worm) can infect fish and if the fish is not properly cooked lead to infection and allergic symptoms in humans. It is more common in Spain, Italy, Japan and Korea and rare in the UK. Symptoms include tummy plan, vomiting and diarrhoea in the case of worm infection, or more typical allergic reactions (rashes) and even anaphylaxis on repeated exposure. Children allergic to anisakis can often eat uninfected fish.
A written management plan will be provided and appropriate medication prescribed which should be available at all times.
If fish is accidentally eaten, spit the food out straight away and give an antihistamine as soon as possible.
- Difficulty breathing (wheezing, noisy breathing).
- Swelling in the throat (noisy breathing, drooling).
- Feeling faint or dizzy, looking very pale (lie the child down with their legs raised).
If any of these severe symptoms occur get help straight away
and dial 999 stating “anaphylaxis” (ana-fil-ak-sis).
It is important to inform the nursery/school and any after-school clubs. Any other carers such as grandparents, relatives and school friends’ parents will also need to know.
Most children with fish allergy will not outgrow the problem. If there has been no reaction for a long time and allergy tests to fish are negative, an oral challenge may be suggested.
There is no cure for fish allergy at present.