Hidden Names for Fish and Shellfish on UK Food Labels

Fish and shellfish hide in surimi, fish sauce, Worcestershire sauce, glucosamine and isinglass. Here are the crustacean and mollusc terms to look for.

Seafood is not one allergen on a UK label, it is three. Fish, crustaceans and molluscs are listed separately, and each hides under names that do not obviously read as seafood. Sauces are a particular trap, because a few drops of an ingredient like fish sauce or anchovy can carry the allergen into a dish that looks entirely meat or vegetable based. This guide explains the three groups and the words that catch people out.

Three separate allergens, not one

It helps to understand how UK law splits seafood:

• Fish covers finned fish such as cod, salmon, tuna, haddock, mackerel and anchovy.
• Crustaceans are the shelled creatures with legs: prawns, shrimp, crab, lobster, langoustine, crayfish and scampi.
• Molluscs are the soft-bodied group: mussels, clams, oysters, scallops, squid, octopus, cuttlefish, snails, cockles and whelks.

Because these are separate allergens, someone may need to avoid one group but not another. That is why a label names the specific group rather than just saying “seafood”.

Hidden names and sneaky sources

Several ingredients carry fish or shellfish without making it obvious:

• Surimi. A processed fish paste used to make seafood sticks, crab sticks and imitation crab. It is fish, even when it is shaped to look like crab.
• Fish sauce, nam pla and nuoc mam. Salty liquids made from fermented fish, common in South East Asian cooking and in many stir-fries, curries and dressings.
• Worcestershire sauce. Traditionally contains anchovies, so it carries fish into cottage pie, marinades, Caesar dressing and savoury cocktail mixes.
• Anchovy in pizza, tapenade, some pasta sauces and salad dressings.
• Caviar and roe, which are fish eggs.
• Bouillabaisse, paella and laksa, dishes that routinely combine fish, crustaceans and molluscs.

Two more terms are worth knowing because they appear in unexpected places:

• Glucosamine is a supplement that is often derived from the shells of crustaceans, so it can be relevant for a shellfish allergy. Check the source on the label.
• Isinglass is a fish-derived substance used to clarify some drinks, including certain beers and wines. It is worth being aware of, though many drinks are now made without it.

Where these allergens turn up unexpectedly

Beyond the obvious seafood dishes, watch for fish and shellfish in:

• Asian sauces and ready meals, where fish sauce is a common background flavour.
• Dressings and condiments, especially Caesar dressing and anything using Worcestershire sauce.
• Stocks and soups, which may use a fish or shellfish base.
• Spreads and pastes, such as anchovy paste or shellfish-based dips.
• Supplements and clarified drinks, via glucosamine and isinglass.

Eating out calls for extra care, since shared fryers and shared utensils can carry seafood across to other dishes.

How the labelling helps

UK law requires fish, crustaceans and molluscs to be declared as three of the 14 allergens and emphasised in the ingredients list of prepacked food, usually in bold. A “may contain” line for any of these is voluntary precautionary labelling, flagging a possible risk of accidental traces rather than a deliberate ingredient. Many people who avoid seafood still treat those warnings as important.

For food prepacked for direct sale, such as a fresh sushi box or a deli sandwich made on the premises, Natasha’s Law requires a full ingredients list with allergens emphasised. That is especially useful for seafood, which appears so often in freshly made food.

The most useful habit here is recognising that surimi, fish sauce, Worcestershire sauce and anchovy all carry the allergen quietly. Read every ingredients list carefully, every time, and check the specific group named. If you want help decoding a label or a hidden seafood term, use The Food Allergy Lab to check before you buy.

Written and reviewed by the Food Allergy Lab editorial team.