Hidden sources of fish, from Worcestershire sauce to kimchi

Updated 2026-08-05

Fish allergy behaves differently from the allergies people usually have in mind. It frequently starts in adulthood, it is often severe, and it is not the same thing as a shellfish allergy despite both arriving on the same menu. It also hides in a set of everyday condiments that almost nobody suspects.

This is general information, not medical advice. Which fish you avoid, and whether you carry epinephrine, is a decision for your allergist.

Fish on a label

Finned fish is one of the major allergens that must be declared in plain language on packaged food sold in the United States, either in the ingredient list or in a "Contains" statement. The UK and EU have equivalent rules, with fish among their fourteen declarable allergens.

Names to watch for beyond the obvious species: anchovy, fish stock, fish sauce, fish flavouring, fish oil, fish gelatin and surimi.

An allergy that often starts in adulthood

Most food allergies are established in childhood. Fish is an exception: in one study, as many as 40% of people reporting a fish allergy had no problem with fish until they were adults. If you have started reacting to fish as an adult, that is not unusual and it is not in your head.

Fish is also often implicated in food-induced anaphylaxis, so this is one to take to an allergist rather than manage by avoidance alone.

Fish allergy is not shellfish allergy

These get bundled together as "seafood", but there appears to be no relationship between fish and shellfish allergies. Being allergic to salmon says nothing about whether prawns are a problem, and vice versa. They are different animals with different proteins. See our shellfish guide for that side of it.

Between fish species it is a different story: more than half of people allergic to one fish are allergic to others, so allergists usually recommend avoiding all finned fish until testing says otherwise. Your allergist can help work out whether particular varieties are safe for you.

Where fish turns up unexpectedly

This is the part that catches people, because none of these announce themselves:

• Worcestershire sauce, which is traditionally made with anchovies, and anything built on it
• Caesar salad and Caesar dressing, also anchovy
• Barbecue sauces and some steak sauces
• Kimchi, which is commonly made with fish sauce, and Southeast Asian dishes generally
• Imitation crab, crab sticks and surimi, which are made from finned fish
• Fish stock in soups, risottos and sauces
• Fish gelatin, made from the skin and bones of fish, used in some sweets, capsules and clarified drinks

Cooking fumes

Unlike most food allergens, fish can be a problem without being eaten. Proteins may be released into the air while fish is being cooked, which is why guidance is to stay out of areas where fish is cooking and, for some people, to avoid seafood restaurants entirely. Ask your allergist whether this applies to you.

How AllergyLens helps

AllergyLens reads the whole ingredient list against a fish profile, including the derived names above, so an anchovy in a Worcestershire-based marinade or surimi in a supermarket crab stick is flagged even when the front of the pack says nothing about fish. It cannot smell a kitchen or check a restaurant's fryer, so cooking fumes and cross-contact are still yours to manage.