🦐Shellfish allergy (crustaceans)
Crustacean allergy — to shrimp, prawns, crab, lobster, crayfish and langoustines — is one of the most common food allergies in adults. It can start at any age, usually lasts for life and can cause severe reactions, so it is managed by avoiding crustaceans completely.
🔬What it means
The immune system mistakes proteins in crustacean meat for a threat and releases chemicals such as histamine. Even a small amount can trigger a reaction in some people, and for some, even the steam from cooking shellfish is enough.
Crustaceans and molluscs (squid, mussels, oysters) are separate allergen groups, but some people react to both. Fish allergy is a different allergy altogether: being allergic to one does not mean you are allergic to the other. An allergist can test which seafood is safe for you.
✅What you can eat
Everything that does not contain crustaceans or traces of them. Plain meat, eggs, dairy, grains, fruit and vegetables are naturally free of them. Whether fish and molluscs are safe depends on your own tests — ask your allergist.
🚫What to avoid
- 🦐Crustaceans in any form: shrimp, prawns, crab, lobster, crayfish, langoustines, scampi, krill.
- 🥘Dishes where they are usual: paella, gumbo, jambalaya, bisque, bouillabaisse, tom yum, laksa, prawn tempura, har gow and other dim sum, seafood pasta and sushi.
- 🥫Hidden sources: shrimp paste (belacan, kapi), dried shrimp, XO sauce, many Thai curry pastes and sambals, seafood stock and flavourings, prawn crackers. Crab sticks (surimi) are made mainly from fish but may contain crab — check the label.
- 🏷️Labels: in the EU and UK crustaceans must be highlighted in the ingredients. “May contain crustaceans” means there is a risk of traces — most allergists advise avoiding these products.
- 🍽️Cross-contact: shared fryers, grills, woks and cooking water in seafood restaurants; fish dishes are often cooked next to prawns. Tell the staff about the allergy every time.
⚠️What happens during a reaction
Symptoms usually start within minutes to two hours: itchy mouth, hives, redness, swelling of the lips or face, stomach pain, vomiting, sneezing or a runny nose.
A severe reaction — anaphylaxis — affects breathing or circulation: swelling of the tongue or throat, hoarse voice, wheezing, difficulty breathing, feeling faint, pale or clammy skin, collapse. It can develop fast and is life-threatening.
A mild reaction in the past does not mean the next one will be mild. Shellfish allergy rarely goes away, so do not try crustaceans again without your allergist.
🚑When to get help urgently
If there are any signs of anaphylaxis, use an adrenaline auto-injector if you have one and call emergency services immediately, even if symptoms improve. Lie down with legs raised (or sit up if it is hard to breathe) and do not stand up suddenly. After any reaction, see a doctor about an allergy plan.
📱How Me Nutrition helps
Every dish in the app and on this site shows the major allergens of a typical recipe, including crustaceans, and which ingredient contains them. Recipes differ and traces are not covered, so always check with whoever cooked the dish.
Dishes that contain it: 213
Sources
Written from the sources below; not reviewed by a doctor. Not medical advice. How we count →