How to read food labels for allergies
Updated October 3, 2026 by Kamal Nasir
On most US packaged food, the law requires the nine major food allergens to be named on the label, either in brackets inside the ingredient list, such as whey (milk), or in a Contains statement next to it. Read the whole ingredient list every time you buy, not only the Contains line, because a Contains statement is not required. A May contain line is voluntary, so a label without one is not a promise that there was no cross contact.
General information, not medical advice. How these guides are made.
The nine major food allergens
Under the Food Allergen Labeling and Consumer Protection Act of 2004 (FALCPA) and the FASTER Act of 2021, the FDA recognises nine major food allergens:
- Milk
- Eggs
- Fish, with the species named, such as bass, flounder or cod
- Crustacean shellfish, with the type named, such as crab, lobster or shrimp
- Tree nuts, with the type named, such as almonds, pecans or walnuts
- Peanuts
- Wheat
- Soybeans
- Sesame
Sesame and allergens outside the nine
Sesame has been required on labels as a major allergen since January 1, 2023, but the FDA notes that some products made before then may still be on sale without it, so check with the manufacturer if you are unsure. The FDA also says more than 160 foods are known to cause food allergies. If yours is not one of the nine, the label does not have to call it out, and you need to read every ingredient.
The two ways an allergen must appear
FALCPA requires the food source of each major allergen to appear at least once on the label. If the ingredient name already says it, as buttermilk does for milk, nothing more is needed. Otherwise it must appear in one of two ways:
- In brackets after the ingredient: lecithin (soy), flour (wheat), whey (milk)
- In a Contains statement next to the ingredient list: Contains wheat, milk and soy
Why one mention is enough to put it back
The FDA gives an example: casein, sodium caseinate and whey are all milk proteins, but the word milk only has to appear on the label once. If you see your allergen named even once, in brackets or in a Contains line, the product contains it.
Contains versus May contain
If a Contains statement is present, it must list every major allergen used as an ingredient. Not every product has one, which is why the FDA advises reading the entire ingredient list.
May contain and Produced in a facility that also uses are different. They are voluntary advisory statements about possible cross contact, for example from shared equipment. They are not required by law and not every manufacturer uses them. The FDA says they must not be misleading and cannot replace good manufacturing practice.
Ingredients are listed by weight
US rules (21 CFR 101.4) require ingredients to be listed in descending order of predominance by weight, so the first ingredient is the largest by weight. An allergen near the end of the list is still in the product: position tells you about quantity, not safety.
What the allergen law does not cover
The FDA applies FALCPA to most packaged foods, but not to meat, poultry and certain egg products (regulated by the USDA), most alcoholic drinks, raw agricultural produce, highly refined oils, or most food sold unpackaged at counters and restaurants. For loose bakery items, the FDA suggests asking store staff.
A routine for every shop
- Read the full ingredient list, not only the Contains line.
- Re-read familiar products: the FDA notes that ingredients can change at any time.
- Treat May contain as information about cross contact, and its absence as no information.
- If you are unsure, do not buy it, or contact the manufacturer or distributor named on the label.
When to see a doctor
A label can help you avoid a food, but only a medical diagnosis can show which foods you react to. The FDA advises anyone with symptoms after eating a food to avoid it and see a healthcare provider for testing. It also stresses that a mild reaction does not mean the allergy is mild, because any reaction can progress to anaphylaxis, which needs emergency treatment.
Reading labels with an app
Litmus Label Reader can help with the reading. It looks a barcode up in a bundled database of about 440,000 US products, or reads the printed ingredient panel with the camera, and shows the ingredient sentence exactly as printed, in label order. It checks every scan against the allergens you tick and sets matching words in red. When nothing matches, it reports no flagged ingredients found and asks you to verify, because a label cannot rule out cross contact.
Questions people ask
What does may contain mean on a food label?
It is a voluntary advisory statement that the product could contain an allergen through cross contact, for example from shared equipment. The FDA says it is not required by law and not all manufacturers use it.
What are the 9 major food allergens?
Milk, eggs, fish, crustacean shellfish, tree nuts, peanuts, wheat, soybeans and sesame. Sesame was added by the FASTER Act and has been labelled as a major allergen since January 1, 2023.
Are ingredients listed in order of amount?
Yes, by weight. US rules require ingredients in descending order of predominance by weight, so the first ingredient weighs the most.