What does 'may contain' actually mean on food packaging?

This phrase causes more confusion than any other on a food label. People with allergies are told to take it seriously and simultaneously suspect it is a company covering itself. Both readings contain something true, and understanding the regulation behind it resolves the question.

Safety

Step by step

1. Know that it is voluntary, and what follows from that.UK law requires the 14 allergens to be declared when they are deliberately used as ingredients. It does not require any statement about accidental cross-contamination. So 'may contain' is something the manufacturer chose to add, having assessed their process, rather than something imposed on them.
2. Treat all the wordings as equivalent.'May contain', 'not suitable for', 'made in a factory that also handles', 'made on equipment that also processes' — there is no regulated hierarchy between them. They all mean the same thing in practice: an assessed cross-contamination risk.
3. Understand the risk is real but variable.A shared production line where the allergen is rinsed between runs is a very different risk from a factory where nuts are handled in the next room. The label does not distinguish, and you cannot tell from outside which one you have.
4. Match your response to the severity of the allergy.For anaphylaxis, avoid products carrying a precautionary warning for that allergen. For a mild, non-anaphylactic reaction, this becomes an individual clinical decision to make with an allergy specialist, not a general rule. Nobody should be told a small amount is fine.
5. Do not read the absence of a warning as safety.A product with no precautionary statement may still be produced on shared equipment; the manufacturer simply has not chosen to say so. This is the most important limitation of the system and it is not widely understood.
6. Contact the manufacturer for products that matter.Most have a consumer allergy contact and will explain their process. For a staple product a household relies on, one email once is worth far more than repeated guesswork at the shelf.
7. Check it every time.A precautionary statement can be added when a manufacturer changes supplier or line, without any other change to the packaging. It is one of the details that changes most quietly.

Tips

• Free-from ranges are made under controlled conditions specifically to avoid this problem and generally do not carry precautionary statements for the allergen they exclude.
• The Food Standards Agency publishes allergy alerts when products are recalled for undeclared allergens. Subscribing is free and takes a minute.
• If you are cooking for someone else, do not make this decision on their behalf. Show them the pack, or tell them what it says, and let them decide.

Common mistakes

• Dismissing it as legal cover — Because it is voluntary, adding it costs the manufacturer sales for no legal benefit. It is generally added because a genuine risk was found, which makes it a more meaningful signal than people assume.
• Assuming no statement means no risk — The system only obliges declaration of deliberate ingredients. Silence about cross-contamination is not a claim of absence, and treating it as one is the more dangerous of the two errors.

Questions people ask