The answer depends on where you live. In the United States, there are 9 officially recognized major food allergens. The European Union requires labeling for 14, and Canada tracks 11 priority allergens. These lists overlap significantly but reflect regional differences in diet and regulation.
The US “Big 9” Allergens
The nine major food allergens recognized in the United States are:
- Milk
- Eggs
- Fish
- Shellfish (shrimp, crab, lobster)
- Tree nuts (almonds, walnuts, cashews, pecans, and others)
- Peanuts
- Wheat
- Soybeans
- Sesame
For years, the US recognized only eight. The Food Allergen Labeling and Consumer Protection Act of 2004 established the original list. Then the FASTER Act of 2021 added sesame as the ninth, with mandatory labeling taking effect on January 1, 2023. Any packaged food or dietary supplement containing sesame must now declare it on the label, either in the ingredients list, in a “Contains” statement, or in parentheses next to an ingredient made from sesame (like tahini).
How Other Countries Define the List
The European Union casts a wider net, requiring labels to flag 14 allergens. The EU list includes everything in the US Big 9 plus five more: celery, mustard, lupin (a legume related to peanuts), molluscs (mussels, oysters, squid, snails), and sulphur dioxide/sulphites when used as preservatives above certain concentrations. The EU also broadens “wheat” to cover all gluten-containing cereals, including rye, barley, and oats.
Canada’s list of 11 priority allergens sits between the two. It adds mustard and sulphites to a list otherwise similar to the US version, and groups crustaceans and molluscs together rather than listing only shellfish. These differences matter if you travel or buy imported foods, because a product labeled “allergen-free” in one country may not meet another country’s standards.
Why These Specific Foods
Food allergies affect roughly 8% of children and nearly 11% of adults in the United States. The foods on these regulatory lists aren’t the only ones that can trigger allergic reactions, but they account for the vast majority of serious cases.
The underlying mechanism is the same regardless of the food. Your immune system produces a type of antibody called IgE, which normally targets parasites and other genuine threats. In a food allergy, IgE mistakenly identifies a harmless food protein as dangerous. Once you eat that food, the protein enters your bloodstream during digestion, and IgE signals your body to release histamine. That histamine release is what causes symptoms like hives, swelling, coughing, wheezing, and in severe cases, a life-threatening reaction called anaphylaxis. Because the IgE antibodies circulate throughout your blood, symptoms can appear across multiple body systems at once.
How Food Allergies Are Identified
If you suspect a food allergy, diagnosis typically involves several steps. A skin prick test places a tiny amount of the suspected food under your skin’s surface. If a raised bump develops, it suggests sensitivity, but a positive skin test alone isn’t enough to confirm an allergy. Blood tests measure IgE antibody levels in response to specific foods, offering another piece of evidence.
Your doctor may also recommend an elimination diet, where you remove suspect foods for a week or two and then reintroduce them one at a time to see which triggers symptoms. This approach has limits: it can’t distinguish a true allergy from a food sensitivity, and it’s not safe if you’ve had a severe reaction in the past. The most definitive test is an oral food challenge, performed in a medical setting. You eat small, gradually increasing amounts of the suspected food under supervision. If no reaction occurs, the food can usually go back into your diet.
Allergy vs. Intolerance
Not every bad reaction to food is an allergy. Food intolerances, like lactose intolerance, involve the digestive system rather than the immune system. They can cause bloating, gas, or diarrhea, but they don’t trigger the IgE-driven histamine response that defines a true allergy. The distinction is important because intolerances are uncomfortable but rarely dangerous, while allergic reactions can escalate to anaphylaxis within minutes.
This is also why sulphites appear on the EU and Canadian lists but not the US list. Sulphite reactions are real and sometimes severe, particularly for people with asthma, but they operate through a different mechanism than classic IgE-mediated allergies. Different countries draw the regulatory line in different places.
What Labels Actually Tell You
In the US, food manufacturers must clearly declare any of the Big 9 allergens on packaged food labels. You’ll see this in one of three ways: the allergen named directly in the ingredients list, a separate “Contains” statement near the ingredients, or the allergen noted in parentheses after a less obvious ingredient name. Tahini, for instance, must now specify “sesame” on the label.
What labels don’t reliably tell you is whether a product was made in a facility that also processes allergens. Statements like “may contain traces of peanuts” are voluntary in the US and not regulated by the FDA. They’re useful as a caution, but their absence doesn’t guarantee the product is free from cross-contact. If you have a severe allergy, contacting the manufacturer directly is often the most reliable way to assess risk.