Fish allergy
Allergy to finned fish, usually lifelong.
About fish allergy
Fish allergy is an allergy to finned fish such as cod, salmon, tuna, haddock and plaice, and it is one of the more common and persistent food allergies, often lasting for life. The main culprit is a muscle protein called parvalbumin, which is very stable and survives cooking, so both fresh and processed fish can cause reactions. The allergy is IgE-mediated: the immune system produces specific antibodies to parvalbumin, and on later exposure these drive a rapid release of histamine and other inflammatory chemicals.
Reactions typically come on fast, often within minutes, and fish is a well-known cause of anaphylaxis, a severe whole-body reaction. Symptoms range from hives, itching and facial swelling to vomiting, wheeze, throat tightness, a drop in blood pressure and collapse. Because parvalbumin is shared across many species, people allergic to one fish are often advised to avoid all finned fish unless testing and specialist advice suggest otherwise. Some people react even to cooking vapours or steam. Importantly, fish allergy is separate from shellfish allergy, though a person can have both.
Diagnosis uses your history with skin-prick or specific-IgE blood tests, and sometimes a supervised challenge. Management is strict avoidance, careful label-reading, and caution with sauces (such as Worcestershire sauce), stocks and cross-contamination in kitchens serving seafood. 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
- All finned fish\nFish sauce and stock\nWorcestershire sauce and some dressings
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.