Fish allergy affects close to 1% of American adults, a little over 2 million people, according to a 2019 national survey led by Ruchi Gupta at Northwestern. It often begins in adulthood. FARE reports that about 40% of people with fish allergy had their first reaction as adults, and for most people it is a lifelong allergy.
A grilled salmon fillet is easy to spot and skip. The trickier exposures come from small amounts of fish used as a seasoning, and the classic example is a bottle that sits in nearly every kitchen and bar: Worcestershire sauce.
What Is Worcestershire Sauce, Exactly?
Worcestershire sauce is a fermented condiment made from vinegar, molasses, tamarind, spices, and, in the traditional recipe, anchovies. The anchovies break down during aging and add a deep savory flavor. The original Lea & Perrins sauce sold in the US lists anchovies in its ingredients and declares fish as an allergen.
It is used a few dashes at a time, which makes it very easy to forget about.
Where Fish Hides
- Worcestershire sauce, and everything made with it: Bloody Marys, steak sauces, burger blends, marinades, and some barbecue sauces.
- Caesar salad and Caesar dressing. Traditional recipes use anchovies or anchovy paste, and many bottled versions do too.
- Fish sauce. Thai nam pla and Vietnamese nuoc mam are made from fermented anchovies and season many Southeast Asian dishes, including pad thai, curries, and dipping sauces.
- Kimchi. Many traditional recipes include fish sauce or other fermented seafood.
- Japanese stocks. Dashi, the base of miso soup and many noodle broths, is usually made with dried bonito flakes.
- Italian dishes. Puttanesca sauce, caponata, and some pizza toppings and tapenades include anchovies.
- Imitation crab. Surimi, the main ingredient in imitation crab and "krab" sticks, is made from fish.
- Gelatin and fish oil. Some gelatins and omega-3 supplements come from fish.
Why It's So Easy to Miss
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It is used as a seasoning. A few drops of fish sauce or Worcestershire are enough to flavor a whole pot, and there are no visible pieces of fish in the finished dish.
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Menus name the dish and skip the condiments. A burger, a Bloody Mary, or a bowl of pho will rarely mention what went into the marinade or broth.
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Different fish can cross-react. The main fish allergen is a protein called parvalbumin, which is similar across many species and holds up well to cooking. FARE notes that more than half of people allergic to one fish react to others, which is why allergists usually advise avoiding all finned fish until testing says otherwise.
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Kitchens share oil and surfaces. Shared fryers are a common source of cross-contact. FARE also notes that steam from cooking fish can carry fish protein. The evidence comes mostly from case reports, but it is worth knowing about if your reactions are severe.
A Few Points Worth Knowing
Fish and shellfish are separate allergies. Finned fish and shellfish are biologically distant, and each allergy needs its own diagnosis. Your allergist can test for both. In practice, seafood restaurants share so much equipment that many people with either allergy avoid both kinds of kitchen.
Labels name the species. US labeling law requires packaged foods to name the specific fish, such as "anchovy" or "cod," following FDA's allergen labeling guidance. That helps if your allergist has cleared certain species.
Canned fish is a special case. The high-heat canning process changes parvalbumin, and a pediatric review found that some children allergic to salmon or tuna tolerated the canned form. This is something to explore only with your allergist, usually through a supervised food challenge.
How to Protect Yourself
- Ask about Worcestershire, fish sauce, and anchovies by name when ordering burgers, steaks, Caesar salads, and Bloody Marys.
- Be especially careful with Thai, Vietnamese, Korean, and Japanese dishes, where fish sauce and dashi are basic ingredients.
- Look for anchovy-free versions. Vegan Worcestershire sauces and fish-free Caesar dressings are widely available. Check the label, since recipes vary by brand and country.
- Read every label, every time.
- Use ForkSure to scan a dish or package for likely fish before you eat. ForkSure flags fish as one of the Big 9.
The Bottom Line
Fish shows up in many kitchens as a seasoning, and seasonings rarely make it onto the menu. A splash of Worcestershire or fish sauce is enough to carry fish into a cocktail, a salad, or a bowl of noodles. Asking about these specific condiments, and reading labels for anchovy and other species, will catch most of them.
Stay safe, and when you need help, scan it with ForkSure.