What is it?

There are 3 different allergens in this category:




What do I need to know?

Molluscs have a varied range of body structures and usually have a shell. Exceptions include octopus and squid, which do not have a shell. There is an estimated 70,000 to 76,000 species worldwide (Rosenburg, 2014)

Crustaceans are a group of animals with skeletons on the outside of their bodies which they then leave as they grow. There are an estimated 45,000 species worldwide (Encyclopaedia Britannica 2018)

Fish, crustaceans and most molluscs live in the seafood or in freshwater environments (e.g. rivers, lakes)

As of March 2020, there are 233,220 marine species registered on the World Register of Marine Species.

Seafood allergy is one of the most common allergies in adults (Allergy UK 2016)

Fish and seafood allergies are more common in adults than children and it tends to be lifelong

People who have an allergy to fish are usually advised to avoid all types of fish as there is a strong likelihood that if they have an allergic reaction to one, they will to another. This is both because of the proteins in fish and also due to cross-contamination. Advice is usually to avoid all types of fish (Anaphylaxis Campaign 2016)

If somebody is allergic to crustaceans or molluscs, this does not mean that they have a higher chance of reacting to fish (Anaphylaxis Campaign 2016)

If you react to one type of seafood/shellfish, it is again likely that you will react to other types, especially in the same group (Anaphylaxis Campaign 2016)

Even the vapours from seafood and fish cooking can sometimes cause an allergic reaction for people who have a severe allergy (Anaphylaxis Campaign 2016)

Since Nov 2005, the law states that companies need to specify crustaceans, molluscs and fish in pre-packed foods (Food Standards Agency 2016)

What are the symptoms?

Can be fatal (anaphylaxis)

Swelling of the lips, tongue and sometimes the throat

Difficulty breathing (especially if the person has asthma)



Stomach cramps/pain



Itchy lumps on the skin (hives)

Runny nose

Flushes to the skin

What should I avoid?

CevicheCured fishFish cakesFish extractsFish fingers and nuggetsFish oils (Piscum lecur)Fish sauceFish spread/pasteAnchovies

Avoid all species of fresh fish, such as:

CodHaddockPlaiceSardinesSea breamSharkSalmonTroutTunaOmega-3 rich oils – derived from fishSmoked fish

Other products containing fish, seafood or shellfish:

Bloody Mary (contain Worcestershire sauce)Bouillabaisse (French fish stew)Caviar (fish eggs)Fish fingersFish pieFishcakesFish stockOyster saucePrawn chipsPrawn crackersRoe (fish eggs)ScampiSeafood chowderShrimp pasteSushiTaramasalata (contains fish eggs)

What should I check?

CasserolesDipsFritto misto (fried fish)Kedgeree (usually contains smoked haddock)Oriental dishes, e.g. Chinese and Thai (use fish sauce)Pasta saucesPates, e.g. salmonPatum Peperium – Gentleman’s Relish (anchovies)Pizza (sometimes have anchovies or other fish as a topping)Salad dressing, e.g. CaesarSeafood dipsSeafood/crab sticksSashimiShepherd’s pie (often contains Worcestershire sauce)

Soups (may use fish sauce or fish stock)StewsSushiWorcestershire sauce (usually contains anchovies)Wine

For seafood/shellfish:

Caponata (seafood salad)CasserolesDips or patesFish fingers and nuggetsFish pie (often contains prawns)Fried riceFruits de mer (seafood)Gumbo (Louisiana stew that often contains seafood)Lancashire hot pot (traditionally contained oysters)Oriental dishes, e.g. Chinese and Thai (often use oyster sauce and seafood)PaellaPasta saucesPizza (sometimes have prawn, calamari or mussels as a topping)Prawn crispsSalad dressing, e.g. CaesarSashimiSeafood dipsSeafood/crab sticksSurimiSoups (may use oyster sauce)StewsWine