Not an ingredient, not a guarantee
'May contain nuts' — or traces of milk, or wheat, or any of the other major allergens — is not telling you the product contains that thing. It means the manufacturer cannot rule out the possibility that it got in. An ingredient declaration is a statement of what was deliberately put into a food. A precautionary allergen label is a statement about the conditions in which that food was made.
The formal term is precautionary allergen labelling, often shortened to PAL. It exists because shared equipment, shared factory lines, or even shared airspace can allow trace amounts of one product to end up in another. A biscuit that contains no nuts as an ingredient might travel down the same production line as one that does. If the manufacturer's risk assessment concludes that a meaningful risk of cross-contact exists, they may add the warning.
Why 'may contain' is voluntary
This is where things get counterintuitive. In the UK, precautionary allergen labelling is not legally required in the same way that ingredient declarations are. Listing actual ingredients is mandatory. Adding a 'may contain' warning is a voluntary, risk-based decision made by the producer. There is no standardised threshold — no specific level of contamination that automatically triggers the phrase.
That voluntary status has a practical consequence: the absence of a 'may contain' statement does not mean a product is safe for someone with a severe allergy. It means the manufacturer assessed their processes and concluded the risk was low enough not to warrant the label. Whether that assessment matches your own risk tolerance is a separate question, and one only you and your medical team can answer.
It also explains why two nearly identical products from different makers can carry very different labels. One factory may have entirely segregated production lines; another may share equipment but use thorough cleaning protocols. Both decisions can be defensible under the same voluntary framework, and both produce a different label.
The problem with inconsistency
Because there is no legal standard for when to add a 'may contain' warning, the phrase has become, in places, overused. Some manufacturers apply it as a blanket precaution on everything made in a facility that handles any of the 14 major allergens — which, in a large food factory, could mean almost everything they produce. When a label appears on products where the actual risk is negligible, it loses meaning for the people who rely on it most.
Allergy UK and the Food Standards Agency have both pushed for more consistency in how PAL is applied, and industry bodies have developed voluntary codes of practice aimed at making the language more meaningful. The FSA website is the right place to follow where that work currently stands.
What to do with the label
For most people, a 'may contain' warning is background noise. For someone managing a food allergy, it demands a different response — it is a starting point, not a conclusion.
Contacting the manufacturer directly is almost always worthwhile. A good producer can tell you specifically which allergens are handled on the same line, how their cleaning processes work, and whether any batches are produced in allergen-free conditions. Many smaller artisan makers, who often have simpler production setups, can give you a level of detail that a large brand's packaging cannot.
Official guidance from the Food Standards Agency and Allergy UK is the right place to ground any allergy management decisions. This article explains the labelling system; it is not a source of advice about individual medical risk.
Where artisan producers fit in
Independent British food makers occupy an interesting position here. A small-batch jam producer working in a dedicated kitchen handles an entirely different level of complexity than a large factory running dozens of lines. That narrower operation can mean clearer information and less risk of inadvertent cross-contact — though it equally means there is rarely a full allergen management team behind the label.
Smaller does not automatically mean safer. What it can mean is more accessible: a real person who made the product and can answer a direct question about it. If you have a genuine allergy concern, that conversation is worth having before you buy, not after.
