What is a shellfish allergy?

A shellfish allergy is an adverse response or overreaction of the body’s immune system to the proteins in shellfish or products that contain shellfish. When shellfish is eaten, the body sees the proteins from shellfish as a foreign invader, sending out chemicals to defend against it. Those chemicals are what cause the symptoms of an allergic reaction. Shellfish allergy is one of the most common allergies, particularly in adults, and is typically life-long. It can also present with severe symptoms like anaphylaxis.


What are shellfish?

Shellfish consist of two groups, molluscs and crustaceans. Molluscs consist of clams, mussels, oysters, scallops and squid, and Crustaceans include but are not limited to crabs, lobsters, prawns, and shrimp.


Crustaceans tend to be responsible for most shellfish reactions. Shellfish are designated as one of top food allergens in the UK and USA, and therefore must clearly be marked on any labelling.


Symptoms of Shellfish Allergy

An allergic reaction to shellfish can bring on many symptoms. These include hives or a skin rash; nausea, stomach cramps, vomiting and/or diarrhoea; stuffy or runny nose, headaches, and asthma.



Although less common, some allergy sufferers are also at risk of having a potentially life-threatening anaphylaxis reaction. 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 is happening. This may lead to collapse and unconsciousness. On rare occasions, death can occur.

It is important to be able to recognize and manage reactions quickly in order to prevent serious health consequences. The first line of action for anaphylaxis is the timely use of epinephrine which is available by prescription in a self-injectable device.

Symptoms of an allergic reaction to food


If you are concerned that you or your child may have an allergy, you should consult with a medical professional or a Registered Nutritionist or Dietitian. If your child is diagnosed with an allergy, it’s important to inform all people involved in the child’s care. This includes their nursery, school, and after-school clubs, as well as grandparents, relatives, and the parents of their school friends.


Managing Shellfish Allergy

Shellfish allergy sufferers should avoid foods that contain crustaceans or any of these ingredients:

  • Barnacle
  • Crab
  • Crawfish (crayfish)
  • Krill
  • Lobster (langoustine)
  • Prawns
  • Shrimp (scampi)

These ingredients may also be present in foods not commonly associated with shellfish such as:

  • Condiments, sauces & dressings
  • Vitamin supplements like calcium and glucosamine
  • Gumbo
  • Bouillabaisse
  • Surimi

You may only be allergic to one type of crustacean, however you should consult your allergist before consuming any other type of shellfish such as molluscs. It may be the case that you can tolerate other shellfish, however you should be wary consuming shellfish in places where you have not prepared it yourself (such as in a restaurant) where the shellfish could be kept together and result in cross-contamination.


Replacements for shellfish products

Shellfish are a good source of protein and complement many dishes very well. If you miss the taste shellfish provides, you can resort one of very many meat-free imitation meats or fish which often provide the same texture as the original. Keep in mind that products like imitation crab meats are not necessarily shellfish free, so be careful when picking alternatives and always read the label.

Depending on the severity of your allergy, and if you are not also allergic to fish, you could use fish as a substitute for shellfish in dishes. Some dishes are easily adaptable. For example a Paella which traditionally contains shellfish, also works very well with chicken or pork, and even vegetarian. Tofu and beans are also good sources of protein which can be used in dishes to replace the texture of seafood.

If you are looking for an easy-to-use tool to avoid shellfish when shopping for food or recipe inspiration, then try the free Spoon Guru app. The app includes Shellfish, Crustacean Shellfish, or Molluscan Shellfish filters, depending on which version of the app you’re using, and will allow you to select whether or not to include or exclude products with ‘May Contain’ warnings depending on your level of sensitivity. You can then search for recipes or products without shellfish, or one of many other food categories. It also includes a handy barcode scanner for quick scanning whilst out shopping.



Please note: This Spoon Guru Fact Sheet should be used as a source of information only. It should not be used as a replacement to nutritional advice from an accredited medical professional.

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