What 'May Contain' Actually Means Under UK Food Labelling

“May contain nuts” is the phrase that causes the most arguments at the supermarket shelf — some people ignore it entirely, others treat it as an absolute ban. Neither instinct is unreasonable, because the label itself doesn’t tell you how likely a reaction actually is. It just tells you the manufacturer hasn’t ruled it out.

This isn’t medical advice on what risk level is right for you — that’s a conversation for your allergist. What follows is what the label legally means and doesn’t mean, so you can make that judgement with actual information.

The two different types of nut labelling

UK food labelling has two entirely separate categories that get lumped together in everyday conversation, but are legally distinct.

• Allergen declarations (mandatory). If a food genuinely contains nuts as an ingredient, this must be listed in the ingredients list and, since Natasha’s Law came into force in October 2021, emphasised (usually bold) on pre-packed food, including pre-packed for direct sale (PPDS) items like sandwiches made on-site. This is a legal requirement with enforcement behind it.
• Precautionary allergen labelling — “may contain” (voluntary). Phrases like “may contain nuts”, “not suitable for nut allergy sufferers”, or “produced in a factory that also handles nuts” are not required by law. Manufacturers add them voluntarily, usually after a risk assessment of their production line, to cover the possibility of cross-contamination.

The key point: the first category is a legal statement of fact. The second is a business’s own risk judgement, and different manufacturers apply wildly different thresholds before reaching for the phrase.

Why “may contain” isn’t consistent between brands

This is the part that trips people up. There’s no single regulated definition of how much accidental nut residue justifies a “may contain” warning. The Food Standards Agency (FSA) publishes guidance for manufacturers on precautionary allergen labelling, encouraging it to be used only where a genuine, assessed risk exists rather than as a blanket legal shield — but it’s guidance, not binding law with a numeric threshold.

In practice, this means:

• One brand might apply “may contain nuts” to an entire product line because one shared conveyor exists somewhere in the factory.
• Another brand making a near-identical product, with tighter segregation controls, might carry no warning at all.
• The same product can occasionally change its labelling between batches if the manufacturer alters its supply chain or production line.

This is why relying purely on “I’ve eaten this brand before with no problem” isn’t a reliable long-term strategy — always check the label on the pack in front of you, not the memory of the one you bought last month.

How to actually use the label

• Read the full ingredients list, not just the allergy box. Sometimes the clearest signal is an ingredient itself (e.g. “almond extract”), not the precautionary statement.
• Distinguish “may contain” from “made in a factory that also processes”. Both are precautionary, but some allergy teams and individuals treat them with different levels of caution — this is a personal risk decision to make with your allergist, not a legal distinction.
• Check every time, even for repeat purchases. Reformulations happen without much fanfare.
• Be extra vigilant with loose, deli-counter and takeaway food. Legal labelling requirements are different (and often less detailed) for food that isn’t pre-packed — this is exactly where verbal communication with staff matters most.
• Contact the manufacturer directly if you need clarity. Most large UK food brands have an allergen line or email; specific questions (“is this made on shared equipment with tree nuts?”) often get more useful answers than the label alone.

Where PPDS labelling changed things

Since Natasha’s Law, food made and packed on the same premises for direct sale — sandwiches, salads, baked goods from an in-store bakery — now needs full ingredient and allergen labelling too, not just a generic sign pointing you to “ask a member of staff”. This closed a significant gap, but precautionary “may contain” statements on PPDS items are still voluntary in the same way as pre-packed goods, so the same judgement calls apply.

Building your own risk tolerance

There’s no universally “correct” answer to whether someone with a nut allergy should eat “may contain” products — it depends on:

• The severity and pattern of previous reactions
• What your allergist has advised based on your specific test results
• Whether you react to trace/airborne exposure or only larger amounts
• How the specific product is made (a chocolate bar on a shared line is a different risk profile to a jar of pesto with pine nuts openly listed)

Many people with milder nut allergies choose to accept “may contain” products after discussing it with their allergy team; many with a history of severe or unpredictable reactions avoid them entirely. Both are legitimate — the label alone can’t make that decision for you.

FAQ

Is “may contain nuts” a legal requirement? No. Unlike a genuine allergen ingredient, precautionary “may contain” labelling is voluntary and added at the manufacturer’s discretion, guided by FSA advice rather than binding regulation with a fixed threshold.

Does “may contain nuts” mean the product definitely has nut traces in it? Not necessarily. It means the manufacturer has identified a plausible route for cross-contamination (shared lines, shared storage, shared suppliers) and has chosen to flag it rather than guarantee its absence.

Why do some products from the same brand have the warning and others don’t? Different products are often made on different production lines or in different factories with different levels of allergen segregation, so the risk — and therefore the labelling — can vary even within one brand’s range.

Should I just avoid everything marked “may contain nuts”? That’s a decision to make with your allergist based on your own history and test results, not a blanket rule that applies to everyone with a nut allergy. Some people can tolerate trace exposure; others cannot.

For more on building a genuinely safe kitchen day to day, see Cooking at Home: The Realities of a Nut-Free Kitchen.