Food allergies: Understanding the nine most common triggers
Medically reviewed by Dr. Betsy Koickel, MD on October 29, 2026.
Key takeaways:
- The most common food allergens include milk, eggs, fish, shellfish, tree nuts, peanuts, wheat, soy, and sesame.
- Food allergy symptoms can range from mild itching or stomach upset to severe, life-threatening reactions.
- Reading allergen labels carefully and getting food allergen testing when needed can help reduce the risk of symptoms.
Food allergies happen when the immune system reacts to a specific food protein as if it were harmful. For some people, a reaction may be mild and short-lived. For others, even a small exposure to an allergen can trigger a serious reaction requiring emergency care.
Understanding the most common food allergens, how they appear on labels, and when to seek medical care can help you make safer choices.
The nine most common triggers
Although many people still refer to the “top eight” food allergens, sesame was added in 2021 as a major food allergen in the U.S. Here is what you should know about each allergen:
Milk: An allergic reaction to milk is most common in children. Milk may appear on food labels as milk, casein, whey, butter, cream, or cheese.
Eggs: An allergic reaction to eggs may cause hives, stomach symptoms, coughing, or swelling. Labels may list egg, yolks, egg whites, albumin, or mayonnaise.
Peanuts: An allergic reaction to peanuts can be severe and may happen quickly after exposure. Peanuts should be clearly listed on packaged food labels.
Tree nuts: Tree nuts include almonds, walnuts, cashews, pecans, and more. Labels should identify the specific tree nut used, not just the general term “nuts.”
Fish: An allergic reaction to fish may be triggered by a specific species such as salmon, tuna, or cod. Labels should list the specific fish in the ingredients.
Crustacean shellfish: Shrimp, crab, and lobster are common shellfish triggers. Shellfish allergy can be serious, and labels should identify the specific shellfish.
Wheat: An allergic reaction to wheat is different from celiac disease or gluten sensitivity. Wheat may appear in bread, pasta, cereals, baked goods, sauces, and breaded foods.
Soy: An allergic reaction to soy may be triggered by soybeans, soy protein, tofu, or soy sauce. Soy is common in processed foods, so careful label reading is important.
Sesame: A sesame allergic reaction may occur after eating sesame seeds, sesame oil, or foods that contain sesame as a flavoring. Sesame must now be listed on packaged food labels.
Reading food labels for allergen information
Allergen labels are one of the most important tools for avoiding accidental exposure and are closely regulated by the FDA. When reading a packaged food label:
- Check both the ingredient list and any “Contains” statement.
- Look for alternate names, such as casein for milk, albumin for egg, or tahini for sesame.
- Recheck labels every time, since ingredients and manufacturing practices can change.
- Be cautious with statements such as “may contain” or “processed in a facility with,” especially if you have had severe reactions.
Food labeling rules apply to many packaged foods, but they do not eliminate every risk. Restaurants, bakeries, bulk bins, and foods prepared outside the home may require extra questions to ensure safety.
When to see a provider about food allergy testing
Consider seeing a healthcare provider if you notice repeated symptoms after eating the same food, such as hives, swelling, vomiting, wheezing, or throat tightness. You should also seek care if a child develops a possible reaction to a common allergen, or if you are unsure whether symptoms are caused by an allergy, intolerance, or sensitivity.
Food allergen testing can be done by an allergist and may include a medical history, skin prick testing, blood testing, or a supervised oral food challenge. Test results should be interpreted by a healthcare professional who can help develop a plan to manage the allergy.
FAQs
Here are some frequently asked questions about the most common food allergens.
What are the most common food allergens?
The most common food allergens include milk, eggs, peanuts, tree nuts, fish, crustacean shellfish, wheat, soy, and sesame. These foods are subject to specific labeling requirements on many packaged foods in the U.S.
What is the difference between a food allergy and food intolerance?
A food allergy involves the immune system and can cause symptoms such as hives, swelling, wheezing, vomiting, or anaphylaxis. A food intolerance does not involve the immune system. For example, lactose intolerance can cause gas, bloating, or diarrhea, but it is not the same as an allergic reaction to milk.
What is the difference between a food allergy and food sensitivity?
A food sensitivity is a broad term often used for symptoms that occur after eating certain foods but are not clearly caused by an allergy involving the immune system. Symptoms may include digestive discomfort, headache, or fatigue.
When should I see a healthcare provider about a potential food allergy?
Seek medical care if symptoms happen repeatedly after eating a specific food. Severe symptoms, such as trouble breathing, throat tightness, or fainting, require emergency care.
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