Food Allergies
The Top 9 Food Allergens Explained
A plain-English breakdown of the nine major allergens, where they hide, and what you need to know about each one.
In the US, nine allergens are responsible for the vast majority of serious allergic reactions, and they're required by law to be clearly labeled on packaged foods. Knowing what each one is, where it hides, and how serious reactions can be is the foundation of allergy-safe cooking.
Milk
Milk allergy is one of the most common food allergies, especially in young children. It's a reaction to the proteins in cow's milk — primarily casein and whey. This is different from lactose intolerance, which is a digestive issue, not an immune response.
Milk shows up in obvious places like butter, cheese, cream, and yogurt, but also in less obvious ones: margarine, caramel, lunch meats, canned tuna, dressings, and many breads. Label words to know: milk, butter, casein, ghee, lactalbumin, lactoglobulin, lactose, nougat, whey, and anything starting with 'lact-'.
Dairy-free isn't always milk-free
Some dairy-free products still contain casein, a milk protein. Always check the allergen statement, not just the marketing claim.
Eggs
Egg allergy is a reaction to proteins in the egg white, though some people react to the yolk too. Most baked goods, pasta, mayonnaise, and many coatings contain eggs. Eggs also hide in some unexpected places: marshmallows, foam on coffee drinks, and some wines and beers clarified using egg whites.
Label words for eggs: egg, egg white, egg yolk, albumin, globulin, lysozyme, mayonnaise, meringue, ovalbumin, ovomucin, ovomucoid, ovovitellin.
Fish
Fish allergy usually refers to finfish: salmon, tuna, halibut, cod, tilapia, bass, and so on. People who are allergic to one type of fish are often allergic to others, so most doctors recommend avoiding all finfish.
Fish hides in Worcestershire sauce, Caesar dressing, some barbecue sauces, and any dish containing fish stock or fish sauce. Restaurants that serve fish in shared fryers are also a risk.
Label words: anchovies, bass, flounder, grouper, haddock, mahi, perch, pollock, salmon, snapper, sole, tilapia, trout, tuna. Also: fish sauce, fish stock, Worcestershire sauce.
Shellfish
Shellfish allergy usually refers to crustaceans: shrimp, crab, lobster, and crayfish. Mollusks — clams, oysters, scallops, squid — are also shellfish but in a different category, and some people react to one but not the other. Many doctors recommend avoiding both.
Shellfish hides in sushi, paella, some soups and stews, bouillabaisse, and dishes cooked in shared oil at seafood restaurants. Cross-contact at restaurants is a significant risk.
Label words: shrimp, crab, lobster, crayfish, crawfish, prawn, barnacle, clam, oyster, squid, scallop, abalone.
Tree nuts
Tree nuts include almonds, cashews, walnuts, pecans, pistachios, Brazil nuts, macadamia nuts, and hazelnuts. People can be allergic to one, a few, or all of them. Most allergists recommend avoiding all tree nuts if someone is allergic to any.
Tree nuts hide in pestos, marzipan, nougat, many Asian dishes, breakfast cereals, granola, flavored coffees, and a huge variety of baked goods. The risk of cross-contact in bakeries is high.
Label words: almonds, cashews, walnuts, pecans, pistachios, hazelnuts, macadamia, Brazil nuts, chestnuts, pine nuts, nut butters, nut oils, marzipan, nougat, praline.
Peanuts
Despite the name, peanuts are legumes, not tree nuts — they grow underground like beans. But peanut allergy is one of the most common and most severe food allergies, and reactions can happen from very small amounts.
Peanuts hide in mixed nuts, many Asian sauces and dishes, some chocolate, candy, baked goods, and anything processed in a facility that handles peanuts. Refined peanut oil is usually safe because the proteins are removed during refining — but cold-pressed or expeller-pressed peanut oil may still contain protein, so check with your doctor.
Label words: peanuts, peanut butter, peanut flour, beer nuts, earth nuts, goober peas, groundnuts, mixed nuts, monkey nuts.
Wheat
Wheat allergy is a reaction to proteins in wheat, including gluten but also other wheat proteins. This is different from celiac disease and non-celiac gluten sensitivity. All three require avoiding wheat, but for different reasons.
Wheat is in bread, pasta, couscous, most baked goods, crackers, and many processed foods. It also hides in soy sauce, malt products, and some medications.
Label words: wheat flour, wheat starch, wheat germ, wheat bran, durum, einkorn, emmer, kamut, spelt, triticale, farro, farina, semolina, bulgur, couscous.
Soybeans
Soy is one of the most pervasive allergens in processed food. It's used in breads, cereals, canned soups, protein bars, condiments, frozen meals, and most fast food.
The hidden soy problem is real. Edamame, miso, natto, tempeh, and tofu are obvious. But soy also hides in protein bars, many breads, some canned tuna, natural flavors, vegetable broth, and vegetable starch.
Label words: soya, soybean, edamame, miso, natto, shoyu, tamari, tempeh, tofu, hydrolyzed soy protein, textured vegetable protein (TVP), soy lecithin, soy flour.
Sesame
Sesame became the ninth major allergen in the US in 2023. It's especially common in Middle Eastern and Asian cuisines, but sesame hides in bread, crackers, chips, hummus, and even some supplements.
Tahini is the most common hidden source — it's in many prepared hummus products and some sauces. Sesame oil is another. Hamburger buns at fast food restaurants frequently have sesame seeds.
Label words: sesame, sesame oil, sesame seeds, tahini, til, gingelly, benne, goma.
The labeling law helps
Since January 2023, US manufacturers must label sesame clearly on packaged foods. Restaurant menus aren't covered by the same law, so always ask.
Frequently asked questions
- If someone is allergic to one allergen, are they more likely to be allergic to others?
- Not necessarily, but some allergens are structurally related and can cross-react. Peanuts and tree nuts are often co-allergies due to processing cross-contact. Fish species often cross-react with each other. Your allergist can test for specific sensitivities.
- Do children outgrow food allergies?
- Some do, especially milk, egg, wheat, and soy allergies. Peanut, tree nut, fish, and shellfish allergies tend to be lifelong. A board-certified allergist can perform tests over time to see if tolerance has developed.
- What's the difference between a food allergy and a food intolerance?
- A food allergy is an immune response that can be life-threatening. A food intolerance is a digestive issue that's uncomfortable but not dangerous. Lactose intolerance, for example, is not the same as a milk allergy.