What does "may contain" mean on food labels?

Updated 29 October 2026 · By IngrediLens

"May contain nuts". "Produced in a factory that also handles milk". "Not suitable for people with an egg allergy". These lines are called precautionary allergen labelling (PAL). They are among the most confusing parts of a food label because they look official but follow almost no rules.

What the warning is meant to say

An allergen that is a real ingredient must be declared in the ingredients list, as explained in how to read allergen labels. A "may contain" line is about something else: cross-contact. The allergen is not in the recipe, but small amounts might get into the food by accident. This can happen through shared production lines, shared equipment, dust in the air, or raw materials that were handled elsewhere.

Food agencies say this warning should only be used after a risk assessment, when a real risk is left over that the business cannot remove. It should not replace good cleaning and separation. The UK Food Standards Agency and the US FDA both say this in their guidance. The FDA adds that advisory statements must be truthful and not misleading.

What the law does and does not say

So "may contain", "may contain traces of", "made on equipment that also processes" and "made in a factory that handles" all mean roughly the same thing. None of them tells you how likely contamination is or how much allergen there might be. Studies that tested products found that some foods with a warning had no detectable allergen and some had a lot. Some foods without a warning also contained allergens.

International work on this is ongoing. FAO and WHO expert consultations have looked at science-based reference doses that could one day support more consistent warnings. For now, consumers have no number on the pack to rely on.

Common wordings you will see

• "May contain nuts / peanuts / milk / sesame"
• "May contain traces of…"
• "Made in a factory / on a line that also handles…"
• "Not suitable for customers with a … allergy"
• "Cannot guarantee nut free" (common in bakeries and restaurants)
• "Free from" claims, which are a different thing: they are positive claims that the business must be able to back up, and they often come with stricter controls.

In other languages: "puede contener (trazas de)" (Spanish), "pode conter" (Portuguese), "kann Spuren von … enthalten" (German), "traces éventuelles de" / "peut contenir" (French), "può contenere tracce di" (Italian).

How to decide: questions to discuss with your allergist

There is no single right answer. These questions help you agree on a personal rule:

1. How severe have my reactions been? People who have had anaphylaxis are usually advised to avoid products with a warning for their allergen.
2. Does the type of product matter? Chocolate, baked goods, cereal bars and loose items from a bakery are often made on shared lines.
3. Is it for a child or for school? Many families and schools use a strict "no may contain" rule for simplicity. See allergies at school.
4. Can I contact the manufacturer? Many companies will explain what the warning means for a specific product: same line or same building, and how they clean.

Whatever you decide, keep your emergency medicine with you. If someone shows signs of anaphylaxis (trouble breathing, swelling of the throat or tongue, feeling faint), use their adrenaline auto-injector and call emergency services.

When you eat out

Restaurants and takeaways often use generic disclaimers such as "all our dishes may contain traces of allergens". These protect the business but do not answer your question. Tell staff about your allergy, ask how the dish is prepared, and show a written card if there is a language barrier. Our guide to restaurant allergy cards explains how.

How IngrediLens helps

IngrediLens flags "may contain" and trace statements separately from real ingredients. You can see at a glance whether your allergen is in the recipe or only in the warning. It recognises the usual wordings in English, Spanish, Portuguese, German, French and Italian, which helps with imported products and when travelling. You choose how to treat these warnings. The app does not decide for you whether a product is suitable, and it can miss text, so always read the pack.