1.3 The Major Allergens and Reaction Symptoms
Key Takeaways
- The U.S. major food allergens are milk, egg, fish, Crustacean shellfish, tree nuts, wheat, peanuts, soybeans, and sesame.
- Labels must identify the species of fish and Crustacean shellfish and the type of tree nut when those major allergens are ingredients.
- Allergic symptoms can affect skin, mouth, breathing, circulation, or the gastrointestinal tract, and hives are not required for anaphylaxis.
- Cooking does not provide a dependable way to remove food-allergen risk.
- A rapid breathing problem, throat symptom, collapse, or serious multi-system reaction after eating requires the emergency plan, not watchful waiting.
The U.S. Major Food Allergens
Federal law identifies nine major food allergens. Learn the complete list and its important category details:
| Major allergen | Examples and exam distinctions |
|---|---|
| Milk | Milk proteins remain in butter, cheese, whey, casein, and lactose-free cow's milk |
| Egg | May appear in mayonnaise, batters, pasta, glazes, and some dressings |
| Fish | The species must be declared on a regulated packaged-food label, such as cod or salmon |
| Crustacean shellfish | Includes shrimp, crab, lobster, and crayfish; the species must be declared |
| Tree nuts | Includes types such as almond, walnut, pecan, cashew, pistachio, and hazelnut; the type must be declared |
| Wheat | Can appear in flour, breading, sauces, soup bases, and standard soy sauce |
| Peanuts | A legume, not a tree nut, but often handled near tree nuts |
| Soybeans | Can appear in tofu, miso, tempeh, soy sauce, textured soy protein, and many processed foods |
| Sesame | Became the ninth major allergen effective January 1, 2023; examples include tahini and sesame oil |
The legal category is Crustacean shellfish, not every animal commonly called shellfish. Mollusks such as oysters, clams, mussels, scallops, squid, and octopus can still cause serious allergies, but they are not part of the federal major-allergen definition. A restaurant must still respond seriously when a guest names one of them.
More than the major nine can cause allergies. The list is a labeling and training priority, not a statement that every other food is harmless. Mustard, celery, corn, fruits, meats, spices, and other foods can be clinically important to an individual guest.
Common hidden sources
The exam favors ingredient recognition over protein chemistry. Memorize practical connections:
- Milk: whey, casein, cheese, butter, cream, yogurt, and some non-dairy products.
- Egg: mayonnaise, meringue, hollandaise, egg wash, fresh pasta, and some batters.
- Fish: anchovy in some Caesar dressings or Worcestershire-style sauces; fish sauce in many recipes.
- Crustacean shellfish: shrimp paste, crab stock, lobster base, and shared seafood equipment.
- Tree nuts: pesto, marzipan, nut flours, praline, and some sauces.
- Wheat: breading, roux, malted or baked products, seitan, and many sauces.
- Peanut: peanut butter, sauces, desserts, garnishes, and shared oil or equipment.
- Soy: soy sauce, tofu, miso, tempeh, edamame, and textured vegetable protein.
- Sesame: seeds, tahini, halva, sesame oil, and seasoning blends.
Examples are clues, never a substitute for the actual label and recipe. Brands and formulations change.
Recognizing a reaction
A food-allergic reaction can involve one or several body systems:
| System | Possible warning signs |
|---|---|
| Skin or mucosa | Hives, flushing, itching, swelling of lips, tongue, or face |
| Airway and breathing | Throat tightness, hoarse voice, trouble swallowing, wheeze, persistent cough, shortness of breath |
| Circulation or nervous system | Dizziness, faintness, confusion, pale or bluish color, collapse |
| Gastrointestinal | Repetitive vomiting, severe cramping, or diarrhea |
| Mouth | Itching or tingling of lips, tongue, or mouth |
Anaphylaxis is a serious reaction that is rapid in onset and may cause death. It may involve breathing or circulation, or a serious combination of symptoms from different systems. Visible hives are not required. A guest who suddenly has throat tightness, trouble breathing, or collapse after eating may be experiencing anaphylaxis even when the skin looks normal.
What not to infer
There is no dependable restaurant rule that a particular visible amount is safe for every allergic person. FDA states that it has not established a threshold level for any major allergen. Do not use unofficial eliciting-dose tables to decide whether residue is acceptable. Do not assume heat makes a food safe: normal cooking may change some proteins, but it is not a dependable allergen-control step.
Similarly, do not ask whether an allergy is severe as a way to reduce controls. The actionable facts are the ingredient to avoid, the operation's ability to control it, and whether emergency symptoms are present.
Fast decision rule
If symptoms are mild and isolated, alert the person in charge and follow the guest's emergency action plan and operation policy. If there is breathing difficulty, throat swelling or tightness, faintness, collapse, or a rapid serious multi-system reaction, activate the emergency plan immediately. Epinephrine is the first-line treatment for anaphylaxis; antihistamines do not replace it.
On exam questions, choose early recognition and decisive escalation over delay, diagnosis, or reassurance.
Current Category Precision
The major-nine list contains categories, not merely nine individual ingredients. Peanut is its own category even though peanuts are legumes. Fish and Crustacean shellfish are separate categories, and mollusks are outside the federal major-nine definition. Tree nuts means the types FDA currently recognizes for major-allergen labeling, not every food with nut in its name. Those distinctions matter when a guest uses a broad term such as nuts or shellfish: staff must clarify the exact foods to avoid and must not narrow the request on the guest's behalf.
FDA's January 2025 Edition 5 guidance reflects its current interpretation of these categories. It explains that milk from ruminant animals other than cows and eggs from birds other than chickens should receive source-specific allergen declarations. It also removes coconut and several other foods from FDA's current Tree Nut List. That labeling change does not make coconut harmless to a person with a coconut allergy. Coconut used as an ingredient ordinarily still appears by its common name in the ingredient list, and restaurant staff must honor the guest's stated restriction even when the food falls outside the major nine. Older packages may also show older declaration practices during a transition, so read the complete current label rather than memorizing a front-panel pattern.
Classification drill
- A shrimp stock involves Crustacean shellfish; an oyster sauce may involve a serious mollusk allergy without being in that major category.
- Almond flour involves a specific tree nut; peanut flour involves the separate peanut category.
- Tahini is a direct sesame ingredient even when no whole seeds are visible.
- Goat-milk cheese still requires a milk-allergy check under FDA's current interpretation; lactose content is a different question.
Recognize Patterns Without Diagnosing
Symptoms do not arrive in a fixed order. One guest may first report mouth tingling and hives, while another develops repetitive vomiting and dizziness, and another has sudden hoarseness with no rash. Staff should observe and report the signs, note how quickly they appeared, alert the person in charge, and follow the emergency plan. They should not decide that a gastrointestinal symptom is only intolerance when it occurs rapidly with skin, breathing, or circulation signs after eating. They also should not wait for several systems to become involved when a severe airway or circulation symptom is already present. Recognition drives escalation; diagnosis belongs to medical professionals.
Which set contains only U.S. major food allergens?
A guest develops sudden throat tightness and dizziness after eating but has no hives. What is the safest interpretation?
Why should a cook not rely on normal cooking to make an allergen-containing ingredient safe?