Squid allergy
Mollusc allergy to squid (calamari).
About squid allergy
Squid, often served as calamari, is a mollusc within the shellfish group, and allergy to it can be significant. Shellfish allergy commonly begins in adolescence or adulthood and is usually lifelong. The reaction is IgE-mediated: the immune system produces antibodies to muscle proteins, chiefly tropomyosin, which trigger a rapid release of histamine and other chemicals when the shellfish is eaten. This protein is heat-stable, so cooked squid can provoke reactions just as raw squid can.
Symptoms typically appear within minutes and may include an itchy mouth, hives, swelling, vomiting, wheeze and anaphylaxis with breathing difficulty or a drop in blood pressure. Because tropomyosin is shared across shellfish, people allergic to squid may also react to other molluscs such as scallop and mussel and, frequently, to crustaceans like prawn and crab; the same protein family also underlies cross-reactivity with house dust mite in some people.
Diagnosis uses skin-prick or specific-IgE blood tests, sometimes with component testing or a supervised challenge to establish which shellfish are safe. Management depends on strict avoidance, careful checking of restaurant dishes and batter, and awareness of cross-contamination, especially where seafood is fried in shared oil. Those at risk of severe reactions carry an adrenaline auto-injector. A severe reaction is a medical emergency: use adrenaline immediately and call 999.
Common triggers
- Squid 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.