The Big 9 allergens: a parent's guide
US law requires food labels to declare nine major allergens: milk, egg, peanut, tree nut, wheat, soy, fish, shellfish and sesame. Sesame became the ninth in January 2023. These must be named in plain English, either in the ingredient list or in a "Contains" statement — but "may contain" warnings are voluntary and unregulated.
Nine allergens account for the large majority of serious food-allergic reactions in the US, and US law treats them differently from every other ingredient.
The nine
Milk · Egg · Peanut · Tree nut · Wheat · Soy · Fish · Shellfish · Sesame
The first eight were fixed by FALCPA in 2004. Sesame joined on 1 January 2023 under the FASTER Act — which matters more than it sounds, because before that it could legally hide inside "spices" or "natural flavor".
What the law actually requires
For these nine, and only these nine, the allergen must appear in plain English — either inside the ingredient list ("whey (milk)") or in a separate Contains statement below it.
This is why an ingredient list can say "sodium caseinate" — a word that gives no hint it is dairy — and still be compliant, as long as a Contains statement names milk.
The plain-English rule is exactly why GreenCheck reads the "Contains" line as carefully as the ingredient list. A product whose ingredients read "sugar, cocoa" but whose label says "Contains: milk" is still AVOID for a milk-allergic child.
The names allergens hide behind
The Contains statement is your shortcut, but it helps to recognise the aliases:
| Allergen | Also appears as |
|---|---|
| Milk | casein, caseinate, whey, lactalbumin, ghee, curds |
| Egg | albumin, globulin, lysozyme, mayonnaise, meringue |
| Peanut | groundnut, arachis oil, "mixed nuts" |
| Tree nut | almond, cashew, walnut, pecan, pistachio, praline, marzipan, nougat |
| Wheat | semolina, durum, farina, spelt, seitan, einkorn |
| Soy | soya, edamame, tofu, tempeh, textured vegetable protein |
| Fish | anchovy (common in Worcestershire sauce and Caesar dressing) |
| Shellfish | crab, lobster, shrimp, prawn, krill, surimi |
| Sesame | tahini, benne, gingelly, sesamol, halvah |
"May contain" is not what most people think
Precautionary statements — may contain, made in a facility that also processes, made on shared equipment — are voluntary and unregulated in the US.
Three consequences follow, and they're the opposite of most people's intuition:
- Their absence proves nothing. A product with no warning may still share a line with your child's allergen.
- Their wording means nothing. "May contain" and "made in a facility with" do not encode different risk levels. They are style choices.
- They are not a legal admission of anything, which is part of why they're applied so inconsistently.
If your child has a severe allergy, treat every precautionary statement as a stop sign, and let your allergist — not a website — set your family's rule.
Introducing allergens is a separate question
Avoiding allergens and introducing them are different topics, and the guidance reversed within the last decade.
The LEAP trial (2015) found that early, sustained peanut introduction substantially reduced peanut allergy in high-risk infants — the opposite of the older advice to delay. NIAID's addendum guidelines now recommend introducing peanut early for infants at risk, with a plan agreed with your pediatrician.
If you have a baby, this is a conversation to have at your next visit rather than something to action from a blog post.
How GreenCheck handles the Big 9
Set a child's allergies and any match forces AVOID — not a warning, not a downgrade. Matching runs against the structured allergen tags, the ingredient text, and any Contains advisory, and it errs toward flagging.
That bias is intentional. A false positive costs you a label check. A false negative costs a lot more. You can see it on real products in the food catalog: set an allergy and watch the grades move.
Sources
- FDA — Food Allergies: What You Need to Know
- FDA — Food Allergen Labeling and Consumer Protection Act (FALCPA)
- FDA — Sesame as the 9th Major Food Allergen (FASTER Act)
- Du Toit et al., "Randomized Trial of Peanut Consumption in Infants at Risk for Peanut Allergy" (LEAP, NEJM 2015)
- NIAID — Addendum Guidelines for the Prevention of Peanut Allergy in the United States
Common questions
Why is sesame the newest major allergen?
Does "may contain" mean the product is unsafe?
Are coconut and peanut tree nuts?
Do the Big 9 cover every allergy?
GreenCheck provides information to help you decide; it is not medical advice. Always read the product label and consult a professional for allergy and medical decisions.