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The 14 UK Allergens

Crustacean Allergen: Prawns, Crab, Lobster & Cross-Contact Prevention

Managing Crustacean Allergen in Your Food Business

Crustaceans include prawns, shrimp, crab, lobster, crayfish, langoustines, and scampi. They are one of the most potent allergen groups, responsible for some of the most severe allergic reactions reported in the UK. Crustacean allergy tends to be lifelong (unlike some childhood food allergies that are outgrown) and can cause anaphylaxis from very small amounts. For food business operators, the challenge is twofold: crustaceans are a premium ingredient that is often handled separately for cost reasons, which helps with allergen control, but they are also present in less obvious forms such as shrimp paste, Thai curry paste, Worcestershire-style sauces, and some Asian condiments. Shared fryers and grills are a significant cross-contact risk in kitchens that serve both crustacean and non-crustacean dishes.

Key takeaways

Crustacean allergy is typically lifelong and can cause severe anaphylaxis from very small amounts of protein.
Shrimp paste, Thai curry pastes, and Asian condiments are the most common hidden sources of crustacean in UK kitchens.
Shared deep fryers are a major cross-contact risk because crustacean protein persists in cooking oil.
Cooking water, steam, and defrost juices from crustaceans can all carry allergenic protein to other foods.

What Counts as a Crustacean and Where They Hide

The crustacean allergen category covers all crustacean species: prawns (all varieties including king prawns, tiger prawns), shrimp, crab (including crab sticks, which despite being made from fish are often processed with crustacean-derived ingredients), lobster, crayfish, langoustines, and scampi. Some customers with crustacean allergy also react to molluscs (mussels, oysters, squid) because the allergenic protein tropomyosin is similar across shellfish groups, but these are separate allergen categories under UK law. Hidden sources are the main risk for kitchens that do not serve whole crustacean dishes. Shrimp paste (commonly used in Thai, Malaysian, and Indonesian cooking) is a concentrated crustacean product found in many curry pastes, pad Thai sauces, and stir-fry sauces. Some Worcestershire sauce recipes include anchovy (fish, not crustacean) but some Asian-style variants contain shrimp or prawn extract. Fish sauce sometimes contains crustacean-derived ingredients. Crab sticks and seafood sticks may contain crustacean extracts. Paella, bouillabaisse, seafood chowder, and bisque often contain crustacean stock even if the visible crustacean pieces are removed for a particular serving.

Cross-Contact Risks Specific to Crustaceans

Crustacean allergen is particularly persistent. Cooking water from prawns or crab retains the allergenic proteins and can contaminate other foods cooked in the same water. Shared deep fryers are a major risk: prawns cooked in tempura batter leave crustacean protein in the oil, which transfers to anything else fried in that oil. Grills and griddles used for both crustacean and non-crustacean items carry cross-contact risk unless thoroughly cleaned between uses. In raw preparation, the juices from defrosting prawns can drip onto other ingredients if stored above them in the fridge. Even steam from cooking crustaceans can carry allergen particles in enclosed kitchen environments. Practical controls include: storing crustaceans on the lowest shelf of fridges and in sealed containers; using dedicated fryers for crustacean dishes or frying non-crustacean items first in clean oil; cleaning grills and cooking surfaces thoroughly with hot soapy water between crustacean and non-crustacean cooking; using separate utensils (tongs, spatulas, slotted spoons) for crustacean dishes; and ensuring that staff wash hands thoroughly after handling crustaceans before touching other ingredients.

Declaration Requirements and Menu Management

Crustaceans must be declared under the Food Information Regulations 2014 whenever they are present as an ingredient. The declaration should specify "crustaceans" as the allergen group. For prepacked foods, the specific species should ideally be named (e.g., "prawns") and "crustaceans" emphasised. For restaurant menus, the simplest approach is to flag all dishes containing any crustacean species. Be especially careful with dishes where crustacean is not the star ingredient: a Thai green curry that uses shrimp paste, a stir-fry sauce that contains prawn extract, or a seafood stock used as the base for a non-seafood dish. These are the declarations most commonly missed. If your kitchen handles crustaceans, even in small quantities as part of sauces or pastes, declare it proactively on your allergen matrix for every dish that could contain it. A "may contain" statement should be used when genuine cross-contact risk exists that cannot be fully eliminated (for example, if non-crustacean dishes are fried in oil that has also been used for prawns and you cannot guarantee a dedicated fryer).
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What to do next

Check all curry pastes and Asian sauces for shrimp or prawn content

Review the ingredient lists and specification sheets of every Thai, Malaysian, Indonesian, and Chinese sauce in your kitchen. Shrimp paste is a standard ingredient in many commercial curry pastes.

Implement a crustacean-dedicated fryer or frying-first protocol

Either designate a fryer exclusively for crustacean items, or always fry non-crustacean items first in clean oil before cooking any crustacean dishes.

Store all crustacean products on the lowest fridge shelf in sealed containers

Prevent defrost juices and raw crustacean liquids from dripping onto other ingredients. Use sealed, clearly labelled containers for all crustacean storage.

Common mistakes to avoid

Mistake
Forgetting to declare shrimp paste in Thai and Asian dishes
Instead
Shrimp paste is a concentrated crustacean product. Any dish made with a curry paste or sauce containing shrimp paste must be declared as containing crustaceans.
Mistake
Assuming crab sticks are crustacean-free because they are made from fish
Instead
Some crab sticks and seafood sticks contain crustacean-derived flavourings or extracts. Always check the specification sheet rather than assuming.

Frequently asked questions

Is someone with a prawn allergy also allergic to crab and lobster?

Very often, yes. The allergenic protein tropomyosin is common across crustacean species. Most people with a prawn allergy will also react to crab, lobster, and other crustaceans. Treat all crustaceans as a single allergen group for kitchen management purposes unless a customer tells you their allergy is limited to a specific species.

Are crustaceans and molluscs the same allergen?

No. Under UK law, crustaceans (prawns, crab, lobster) and molluscs (mussels, oysters, squid, snails) are separate allergen categories. However, some individuals with crustacean allergy also react to molluscs because the allergenic proteins are structurally similar. Always ask the customer about both groups.

Does cooking destroy crustacean allergen?

No. Crustacean allergen proteins, particularly tropomyosin, are heat-stable and survive boiling, frying, baking, and grilling. Cooking does not make crustacean dishes safe for someone with a crustacean allergy.

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Crustacean Allergen: Prawns, Crab, Lobster & Cross-Contact Prevention | Allergen Management | Paddl | Paddl