Mussel allergy
Mollusc allergy to mussels.
About mussel allergy
Mussels are a mollusc shellfish, in the same broad group as oysters, clams, squid and octopus, and separate from crustaceans such as prawns and crab, although a person can be allergic to both. As with other shellfish, the main allergen is tropomyosin, a stable muscle protein that survives cooking, so cooked and raw mussels can both trigger reactions. The allergy is IgE-mediated: the immune system makes antibodies to tropomyosin and related proteins, and later exposure prompts a rapid release of histamine and other chemicals.
Reactions usually come on quickly, often within minutes, and can be severe, including anaphylaxis. Symptoms may include hives, swelling of the lips and face, vomiting, wheeze, throat tightness, a drop in blood pressure and collapse, as well as milder skin and gut upset. Because tropomyosin is shared across molluscs, people allergic to mussels may react to other molluscs, and there can be overlap with crustaceans and with dust-mite allergy, which shares a similar protein. Shellfish can also cause food poisoning from toxins or bacteria, which is separate from allergy.
Diagnosis uses your history with skin-prick or specific-IgE testing, and sometimes a supervised challenge. Management is strict avoidance of mussels, and usually other molluscs, with careful label-reading and caution over sauces, stocks and cross-contamination in seafood kitchens. Anyone at risk of anaphylaxis should carry an adrenaline auto-injector. A severe reaction is a medical emergency: use the injector and call 999 immediately.
Common triggers
- Mussel and products containing it
Symptoms
- Itching or tingling in the mouth
- Hives, itching or eczema
- Swelling of the lips, face, tongue or throat
- Stomach cramps, nausea, vomiting or diarrhoea
- Wheezing or trouble breathing
- In severe cases, anaphylaxis
Avoidance & management
- Read ingredient labels every time
- Ask about ingredients and cross-contamination when eating out
- Keep the food out of shared cooking areas
- Carry prescribed antihistamines or an adrenaline auto-injector
- Seek emergency help for any severe reaction
Sources & references
Allergy safety: what everyone should know
Mild-to-moderate reaction signs
- Itching, hives or a raised rash
- Swelling of lips, face or eyes
- Tingling mouth, sneezing, runny nose
- Stomach pain, nausea or vomiting
Anaphylaxis — call 999 (UK) or 112 (EU) immediately
- Difficult or noisy breathing, wheeze, persistent cough
- Swelling of the tongue or tightness in the throat
- Dizziness, collapse, pale and floppy (young children)
- Use an adrenaline auto-injector (e.g. EpiPen) at once if prescribed, then call an ambulance even if symptoms improve
Allergy or intolerance? A true allergy involves the immune system and can escalate quickly; an intolerance (e.g. lactose intolerance) is unpleasant but not life-threatening. The symptoms overlap, so self-diagnosis is unreliable.
Getting tested: home-testing kits based on IgG are not diagnostically valid. If you suspect an allergy, ask a GP for referral to an allergy clinic for skin-prick or specific-IgE testing and a supervised food challenge where appropriate.