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Reading food labels: the nine major allergens and "may contain"

What US law requires a label to say, what precautionary statements do and do not mean, and what studies show about how little of an allergen can cause a reaction.

4 minute read9 sources, each checked word for wordLibrary checked October 16, 2026

In short

  • US law names nine major food allergens: milk, egg, fish, crustacean shellfish, tree nuts, wheat, peanuts, soybeans and sesame.Official text1
  • Sesame became the ninth major allergen under the FASTER Act, effective January 1, 2023.Official text2
  • "May contain" and "made in a facility" statements are not required by law.Official text2
  • A study of products with peanut advisory labels found detectable peanut in 10% of them.E2Good3

How sure each claim is:E1StrongE2GoodOfficial textReviewWhat the grades mean

What must a US food label say?

The Food Allergen Labeling and Consumer Protection Act of 2004 named eight major food allergens: milk, eggs, fish, crustacean shellfish, tree nuts, peanuts, wheat and soybeans.Official text2

The FASTER Act added sesame as the ninth. The change applies to foods introduced into interstate commerce on or after January 1, 2023.Official text4

The law requires the label to name the type of tree nut (for example almond, pecan or walnut). It must also name the species of fish and crustacean shellfish (for example cod, crab or shrimp).Official text2,5

One way a label can meet the law is the word "Contains" followed by the food source. This statement goes right after or next to the ingredient list, in type no smaller than the ingredients.Official text5

Flavorings, colorings and incidental additives that contain a major allergen must be labeled too.Official text5

The legal definition has an exception. Highly refined oils made from a major allergen, and ingredients made from those oils, are not counted as major allergens.Official text1

What do "may contain" statements mean?

The FDA explains that advisory statements such as "may contain" or "produced in a facility that also uses" an allergen are not required by law. They may be used for unavoidable cross-contact, only when the maker has taken every precaution against it.Official text2

In a study of 200 products with peanut advisory labels, peanut protein was found in 20 of them (10%). The authors considered the amounts in 13 of them clinically significant.E2Good3

The same study found that people with food allergy were increasingly ignoring advisory labels. It also found that such foods can contain detectable peanut, so eating them carries a risk.E2Good3

Australian researchers noted that precautionary labels have multiplied so much that they cut the choice of foods available to people with allergies.E2Good6

A 2026 World Allergy Organization panel strongly agreed that precautionary labels should be used only when an allergen may be present above a set cut-off. It agreed this use should be based on a formal risk assessment and required by law.E2Good7

The panel also agreed that a precautionary label should never appear for an allergen already listed as an ingredient. Nor should one appear on a product declared "free from" that allergen.E2Good7

How little of a food can cause a reaction?

Researchers describe this with "eliciting doses." An eliciting dose is the amount of allergen protein expected to cause objective symptoms in 1% (ED01) or 5% (ED05) of people with that allergy. These numbers are increasingly used for labeling rules.E1Strong8

Researchers pooled many food challenge studies. They estimated the ED01 at 0.2 mg of protein for peanut and 0.1 mg for cow's milk. It was 0.03 mg for egg and 0.1 mg for hazelnut.E2Good6

An updated analysis of 14 priority allergens found ED01 values from 0.03 mg for walnut protein to 26.2 mg for shrimp protein.E2Good9

In one analysis of individual patients' challenge data, 4.5% of people reacted to 5 mg or less of peanut protein with anaphylaxis.E1Strong8

These are population numbers from research, used to set labeling rules. They do not show how much any one person can eat. Only a clinician who knows the person can talk through that.

What is not known yet

Experts still debate where label cut-offs should sit. The 2026 panel judged the ED05 preferable to the ED01, to balance protection against the overuse of precautionary labels.E2Good7

Questions you might bring to your clinician

  1. How strictly should precautionary ("may contain") labels be treated for this allergy?
  2. Are highly refined oils from this food a concern in this case?
  3. Which foods carry a higher chance of cross-contact for this allergen?
  4. Who else (school, family, caregivers) needs to know how to read labels for this allergy?

Every claim in this guide was written from its sources and checked against them word for word. Its clinical review by Dr. Recio, whose specialty is anesthesia, is pending; an allergist has not yet reviewed it. This line changes when each review is done.

Sources

Each source opens on PubMed, DailyMed or the publisher's page. Under each one are the exact words from it that this page relies on, copied word for word and checked against the original.

  1. 21 U.S.C. 321(qq), definition of major food allergen (current, as amended by the FASTER Act). U.S. Code, 2023. Official text Law or regulation
    The words this page rests on
    Milk, egg, fish (e.g., bass, flounder, or cod), Crustacean shellfish (e.g., crab, lobster, or shrimp), tree nuts (e.g., almonds, pecans, or walnuts), wheat, peanuts, soybeans, and sesame.
    A food ingredient that contains protein derived from a food specified in paragraph (1), except the following:
    Any highly refined oil derived from a food specified in paragraph (1) and any ingredient derived from such highly refined oil.
  2. Food Allergies (FDA consumer and industry page). U.S. Food and Drug Administration, 2026. Official text Law or regulation
    The words this page rests on
    On April 23, 2021, the Food Allergy Safety, Treatment, Education, and Research (FASTER) Act was signed into law, declaring sesame as the 9th major food allergen recognized by the United States. The change was effective on January 1, 2023.
    Consumers may also see advisory statements such as “may contain [allergen] or “produced in a facility that also uses [allergen].” Such statements are not required by law and can be used to address unavoidable “cross-contact,” only if manufacturers have incorporated good manufacturing processes in their facility and have taken every precaution to avoid cross-contact that can occur when multiple foods with different allergen profiles are produced in the same facility using shared equipment or on the same production line, as the result of ineffective cleaning, or from the generation of dust or aerosols containing an allergen.
    Congress passed the Food Allergen Labeling and Consumer Protection Act of 2004 (FALCPA). This law identified eight foods as major food allergens: milk, eggs, fish, Crustacean shellfish, tree nuts, peanuts, wheat, and soybeans.
    The law also requires that the type of tree nut (for example, almonds, pecans, walnuts), and the species of fish (for example, bass, flounder, cod) and Crustacean shellfish (for example, crab, lobster, shrimp) to be declared.
  3. Consumer attitudes and risks associated with packaged foods having advisory labeling regarding the presence of peanuts. Hefle SL, J Allergy Clin Immunol, 2007. E2Good Observational study
    The words this page rests on
    Peanut protein was detected in 10% (20/200) of total food products bearing advisory statements, although clinically significant levels of peanut (>1 mg of peanut or >0.25 mg of peanut protein) were detected in only 13 of 200 such products.
    Consumers with food allergy are increasingly ignoring advisory labeling. Because food products with advisory labeling do contain detectable levels of peanuts, a risk exists to consumers choosing to eat such foods.
  4. Food Allergy Safety, Treatment, Education, and Research (FASTER) Act of 2021, Public Law 117-11. U.S. Congress, 2021. Official text Law or regulation
    The words this page rests on
    (a) In General.--Section 201(qq)(1) of the Federal Food, Drug, and Cosmetic Act (21 U.S.C. 321(qq)(1)) is amended by striking ``and soybeans'' and inserting ``soybeans, and sesame''.
    Effective Date.--The amendment made by subsection (a) shall apply to any food that is introduced or delivered for introduction into interstate commerce on or after January 1, 2023.
  5. Food Allergen Labeling and Consumer Protection Act of 2004 (FALCPA), Title II of Public Law 108-282 (text as posted by FDA). U.S. Congress, 2004. Official text Law or regulation
    The words this page rests on
    provided that in the case of a tree nut, fish, or Crustacean shellfish, the term `name of the food source from which the major food allergen is derived' means the name of the specific type of nut or species of fish or Crustacean shellfish.
    the word `Contains', followed by the name of the food source from which the major food allergen is derived, is printed immediately after or is adjacent to the list of ingredients (in a type size no smaller than the type size used in the list of ingredients) required under subsections (g) and (i); or
    a flavoring, coloring, or incidental additive that is, or that bears or contains, a major food allergen shall be subject to the labeling requirements of this subsection.
  6. Allergen reference doses for precautionary labeling (VITAL 2.0): clinical implications. Allen KJ, J Allergy Clin Immunol, 2014. E2Good Observational study
    The words this page rests on
    There has been a dramatic proliferation of precautionary labeling by manufacturers to mitigate the perceived risk from low-level contamination from allergens in food. This has resulted in a significant reduction in choice of potentially safe foods for allergic consumers.
    Thus by combining data from all studies, the eliciting dose for an allergic reaction in 1% of the population estimated for the following were 0.2 mg of protein for peanut, 0.1 mg for cow's milk, 0.03 mg for egg, and 0.1 mg for hazelnut.
  7. World Allergy Organization (WAO) Consensus on the use and practice of precautionary allergen labelling: The international ACT-UP! e-Delphi. Bognanni A, World Allergy Organ J, 2026. E2Good Consensus statement
    The words this page rests on
    The panel strongly agreed that PAL should only be applied when an unintended allergen may be present above a cut-off (action level) and that it should always be based on a formal risk assessment, preferably quantitative, and mandated through legislation.
    Finally, PAL should not be used for an allergen declared to be absent with a "free from" statement, nor should a PAL appear for an allergen listed as an ingredient.
    Furthermore, action levels should be based on "reference doses" (amount of total allergenic protein), rather than on a concentration (eg, 10 ppm), and more specifically on population-adjusted eliciting doses ED05 (amount of allergen expected to elicit an objective reaction in no more than 5% of the allergic population). To achieve a balance between protection and the risk of PAL overuse, ED05 was deemed preferable to ED01.
  8. Using data from food challenges to inform management of consumers with food allergy: A systematic review with individual participant data meta-analysis. Patel N, J Allergy Clin Immunol, 2021. E1Strong Meta-analysis
    The words this page rests on
    Eliciting doses (EDs) (eg, ED01 or ED05 values, which are the amounts of allergen expected to cause objective symptoms in 1% and 5% of the population with an allergy, respectively) are increasingly being used to inform allergen labeling and clinical management.
    At individual participant data meta-analysis, 4.5% (95% CI, 1.9% to 10.1%) of individuals reacted to 5 mg or less of peanut protein with anaphylaxis (moderate heterogeneity [I2 = 57%]).
  9. Updated population minimal eliciting dose distributions for use in risk assessment of 14 priority food allergens. Remington BC, Food Chem Toxicol, 2020. E2Good Observational study
    The words this page rests on
    Updated ED01 estimates ranged between 0.03 mg for walnut protein and 26.2 mg for shrimp protein. ED05 estimates ranged between 0.4 mg for mustard protein and 280 mg for shrimp protein.