Fish and shellfish allergy

Greater numbers of people are finding that they have an allergy to fish and/or shellfish. Around 1 in 200 people are allergic to fish (such as cod and salmon), whereas allergies to shellfish (such as prawns and crab) are more common – affecting 1% of the population. You can develop a fish allergy at any age and it is likely that you’ll have it for life. It is quite common for people allergic to shellfish to be able to eat finned fish (such as salmon and cod) as the two allergies are usually experienced separately from each other. However, children may be more susceptible to an allergy to both fish and shellfish so extra care should be taken. You should be aware that there is a risk of cross-contamination in restaurants, markets and open fish counters so if you do suffer from either allergy it is important that you keep this in mind.

Fish allergy

Fish and shellfish allergiesAn allergy to fish usually means you are allergic to most species of finned fish, including cod, tuna, hake and salmon. For safety reasons, doctors will usually recommend you avoid all types of fish.

Shellfish allergy

An allergy to shellfish is more common and there are generally 4 types of shellfish that people react to. These are:

  • Arthropods (Crustaceans), such as e.g. crab, lobster, crayfish, shrimp, and prawn.
  • Molluscs (Bivalves), such as mussels, oysters, scallops and clams.
  • Molluscs (Gastropods), such as limpets, periwinkles, and snails.
  • Molluscs (Cephalopods), such as squid, cuttlefish, and octopus.

People who have reacted to one type of shellfish are likely to react to other members of the same group. For example, if you’re allergic to crab then you may react to other crustaceans such as lobster and prawn. It is therefore important for you to avoid all shellfish within the group that you have an allergy to. Allergy tests (such as those detailed within this section) may help to predict which types of shellfish you will react to, but, if in doubt, it may be best to avoid all shellfish.


The symptoms of food and shellfish allergies can range from relatively mild to life-threatening. However, the likely effects are:

  • nausea (feeling sick)
  • vomiting (being sick)
  • diarrhoea
  • abdominal cramps (stomach pain)
  • shortness of breath
  • rhinitis (sneezing and a blocked or itchy nose)
  • urticarial rashes (red, raised and itchy skin)
  • swelling which usually affects the mouth, lips and eyes. In severe cases, a fish or shellfish allergy can lead to anaphylaxis.

Anaphylaxis is a medical emergency and help should be sought immediately from a qualified medical professional. Symptoms of anaphylaxis include itchy skin, swollen hands, feet and face, feeling faint, fainting and unconsciousness. Anaphylaxis can be life-threatening and it is important for people who may be at risk of having a severe allergic reaction to carry injectable epinephrine (such as an EpiPen or Anapen) with them at all times. It is also advisable to wear an identification bracelet stating the food sensitivity.

Food to avoid

In addition to avoiding the fish or shellfish you are allergic to, you should also be aware that traces of fish and shellfish can be found and used in many other products. It is extremely important to read the food packaging labels carefully to check for any fish or shellfish related ingredients and to ensure that you check what is in your food when you are eating out. Many restaurants are well equipped to deal with food allergies but if you’re not sure, contact the place that you intend to eat at prior to your arrival. This way you can ensure your dietary needs can be met.

This is particularly important if when consuming fried food as the oil used to cook shrimp could also be used to cook fried chicken or French fries.

Pregnant women

Current advice to pregnant women is to continue to eat a healthy varied diet while pregnant. This can include cooked shellfish and fish; current research has found no link between avoiding certain foods and your child developing an allergy. Pregnant women are advised not to consume shark, swordfish, marlin or any raw shellfish or fish due to the risk of food poisoning. They are also advised not to consume more than 2 tuna steaks a week due to the high levels of mercury in these fish species.

If you suspect that you may be allergic to fish or shellfish, it is important to speak to your doctor or another health professional to confirm this.

Sources used in the writing of this article are available on request

Information contained in this Articles page has been written by talkhealth based on available medical evidence. Our evidence-based articles are certified by the Information Standard and our sources are available on request. The content is not, though, written by medical professionals and should never be considered a substitute for medical advice. You should always seek medical advice before changing your treatment routine. talkhealth does not endorse any specific products, brands, or treatments.

Information written by the talkhealth team

Last revised: 16 March 2016

Next review: 16 March 2019