The FDA recognizes nine food groups as major allergens: milk, eggs, fish, shellfish, peanuts, tree nuts, wheat, soybeans, and sesame. Together, these nine groups account for roughly 90% of all food allergic reactions in the United States. Any packaged food containing protein derived from one or more of them must say so on the label.
What surprises most people is how many everyday products contain these allergens in forms you wouldn’t expect. Here’s a breakdown of each allergen group and where it shows up.
The Big 9 Allergens at a Glance
- Milk
- Eggs
- Fish (such as bass, flounder, cod)
- Crustacean shellfish (such as crab, lobster, shrimp)
- Tree nuts (such as almonds, walnuts, pecans)
- Peanuts
- Wheat
- Soybeans
- Sesame
The first eight were established by the Food Allergen Labeling and Consumer Protection Act (FALCPA) of 2004. Sesame was added by the FASTER Act, signed into law in April 2021 and enforceable on food labels starting January 1, 2023.
Milk: Far More Than Dairy Products
Milk is one of the most widespread hidden allergens in processed food. Obviously it appears in cheese, yogurt, butter, cream, and ice cream. Less obviously, it turns up in hot dogs, sausages, deli meats, margarine, nougat, and many baked goods. Chocolate frequently contains milk solids even when it isn’t labeled “milk chocolate.”
On ingredient lists, milk protein hides under many names: casein, caseinates (sodium, calcium, or potassium), whey, whey protein concentrate, lactalbumin, and lactoglobulin. Artificial butter flavoring, caramel flavoring, brown sugar flavoring, and “natural flavors” can all be milk-derived. Even some high-protein flours contain milk ingredients. If you’re managing a milk allergy, scanning for the word “milk” alone isn’t enough.
Eggs, Wheat, and Soy
Eggs appear in pasta, baked goods, mayonnaise, salad dressings, meatballs, and many breaded or battered foods. Some egg-based ingredients aren’t immediately recognizable: albumin, globulin, lysozyme, and lecithin (though lecithin more commonly comes from soy). Meringue powder, used in icings and candy, is essentially dried egg white.
Wheat shows up well beyond bread and pasta. It’s used as a thickener in soups, sauces, and gravies. Soy sauce typically contains wheat. Couscous is made from wheat. Many processed meats use wheat-based fillers, and wheat starch appears in some candies and licorice.
Soybeans are equally pervasive. Soybean oil is a standard cooking oil in restaurants and packaged snacks. Soy protein, soy lecithin, and soy flour appear in energy bars, cereals, infant formulas, and canned tuna. Tofu, tempeh, miso, and edamame are obvious sources, but soy also hides in vegetable broth, “natural flavors,” and many Asian sauces and condiments.
Peanuts and Tree Nuts
Peanuts are legumes, not true nuts, but they’re one of the most potent allergens. Beyond peanut butter, they appear in many Asian and African cuisines, baked goods, candy bars, ice cream, and trail mixes. Some chili recipes use peanut butter as a thickener. Peanut flour is increasingly used in high-protein snacks.
Tree nuts include almonds, walnuts, pecans, cashews, pistachios, macadamia nuts, Brazil nuts, hazelnuts, and pine nuts, among others. Labels must name the specific tree nut rather than just saying “tree nuts.” Notably, the FDA recently updated its guidance: coconut is no longer classified as a tree nut for allergen labeling purposes, and neither are chestnuts, hickory nuts, shea nuts, or several other less common nuts.
Tree nut oils and butters appear in baked goods, pesto (pine nuts), marzipan (almonds), pralines, and many desserts. Nut-based milks and flours are also becoming more common in packaged foods.
Fish, Shellfish, and Sesame
Fish and crustacean shellfish are treated as separate allergen categories. Someone allergic to shrimp isn’t necessarily allergic to salmon, and vice versa. The FDA requires manufacturers to list the specific species on the label. A product can’t just say “fish” or “shellfish.” It must say “cod,” “shrimp,” or whatever species is actually in the food.
Fish can appear in Worcestershire sauce, Caesar salad dressing, and some Asian sauces like fish sauce and oyster sauce. Surimi (imitation crab) is made from fish, usually pollock. Shellfish derivatives show up in some glucosamine supplements and bouillabaisse.
Sesame, the newest addition to the list, is common in hummus, tahini, falafel, halvah, and many Middle Eastern and Asian dishes. Sesame seeds top burger buns, bagels, and breadsticks. Sesame oil is used in stir-fries and dressings. Before 2023, sesame could hide in vague label terms like “spices” or “natural flavors.” Now it must be explicitly declared.
How Allergen Labels Work
Manufacturers can declare a major allergen in two ways. The first is in parentheses right after the ingredient name, such as “whey (milk)” or “tahini (sesame).” The second is a separate “Contains:” statement immediately after the ingredient list, such as “Contains: milk, wheat, soy.”
For fish, shellfish, and tree nuts, the label must go further and identify the exact species or type. You’ll see “Contains: tree nuts (cashews)” or “Contains: fish (anchovy)” rather than just the broad category.
One important exception: highly refined oils derived from a major allergen (like highly refined soybean oil or peanut oil) are generally exempt from allergen labeling. The refining process removes nearly all of the allergenic protein. Cold-pressed or expeller-pressed oils, however, may still contain enough protein to trigger a reaction and would need to be labeled.
“May Contain” Warnings Are Voluntary
You’ve probably seen labels that say “may contain peanuts” or “produced in a facility that also processes tree nuts.” These advisory statements are completely voluntary. The FDA does not require them, and there’s no standard threshold or format for them. A company that makes both peanut butter crackers and plain crackers on the same equipment might add an advisory label, but it doesn’t have to.
The FDA does require that these voluntary statements be truthful and not used as a substitute for proper manufacturing practices. Companies are supposed to take every reasonable precaution against cross-contact before relying on an advisory label. Still, because the statements aren’t regulated the same way mandatory allergen declarations are, they vary widely in how they’re applied. Some products carry them out of extreme caution, while others with similar cross-contact risks don’t include them at all. For people with severe allergies, this inconsistency is one of the biggest gaps in the current labeling system.
Foods That Contain Multiple Allergens
Many common foods contain two, three, or even more of the Big 9. Baked goods frequently combine wheat, eggs, milk, and tree nuts or peanuts. Asian stir-fry sauces may contain soy, wheat, fish, sesame, and shellfish in a single bottle. Granola bars often include wheat, soy, tree nuts, and milk. Processed foods with long ingredient lists are the most likely to contain multiple allergens, which is why the “Contains:” line at the bottom of the label exists: it gives you a quick summary without forcing you to decode every ingredient.
Over 160 foods can cause allergic reactions, but these nine groups dominate. If you’re reading labels for yourself or someone in your family, the “Contains:” statement is your fastest tool. For anything without standardized packaging (bakery items, restaurant food, bulk bins), you’ll need to ask directly, since allergen labeling rules apply only to packaged foods regulated by the FDA.