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How often does a food label say “may contain”, allergen by allergen?

Tree nuts are named in a “may contain” line on 117,647 products in Open Food Facts, 2.9 times as many as list them in the recipe.

By Bravoora teamPublished 19 October 2026Sources checked 13 October 20266 min read

Warnings outnumber recipes for tree nuts, peanuts, sesame and lupin; milk and gluten are the reverse. Data: Open Food Facts (ODbL), read 13 October 2026.

Key takeaways

Open Food Facts records the “may contain” line in a traces field: it names tree nuts on 117,647 product records, then soy (85,494) and milk (74,440).
For eight allergens the warning is at least twice as common as the allergen in the recipe: lupin, sesame, molluscs, tree nuts, peanuts, mustard, crustaceans and celery.
Milk and gluten are the reverse: 192,782 records list milk in the recipe and 74,440 warn of it; for gluten, 145,306 and 61,043.
“May contain” is voluntary in the EU, the UK and the US, and no legal threshold triggers it: two factories with the same risk can print different labels.
For an allergy it deserves the same care as “contains”; Bravoora keeps the two apart, Not for you when the allergen is listed, Heads up when only a warning names it.

The short answer

Tree nuts are the allergen a “may contain” line names most: 117,647 products in Open Food Facts, against 41,106 that list them in the recipe. For eight of the 14 allergens the warning outnumbers the recipe at least twofold, led by lupin (7.1 times). For milk and gluten it is the reverse.

Which allergens do “may contain” lines name most often?

Tree nuts, by a wide margin: Open Food Facts’ traces field, where it records the “may contain” line, names them on 117,647 product records^[1]. Then come soy (85,494), milk (74,440), gluten (61,043) and eggs (56,374). Lupin, the least named, is on 8,534. For the names behind the group, Bravoora’s dictionary lists the 49 names that contain tree nuts.

The 14 allergens in Open Food Facts: products that list each in the recipe, and products that warn of it (read 13 October 2026)
Allergen	In the recipe	In a “may contain” line	Warnings for each recipe
Tree nuts	41,106	117,647	2.9
Soy	73,418	85,494	1.2
Milk	192,782	74,440	0.4
Gluten	145,306	61,043	0.4
Eggs	54,783	56,374	1.0
Sesame	11,789	48,128	4.1
Mustard	16,806	40,764	2.4
Peanuts	14,151	40,331	2.9
Celery	15,592	33,146	2.1
Fish	19,614	17,967	0.9
Crustaceans	6,588	15,606	2.4
Molluscs	3,801	12,124	3.2
Sulphites	18,442	10,878	0.6
Lupin	1,196	8,534	7.1

For which allergens do warnings outnumber recipes?

For eight of the 14. Lupin is named in a warning 7.1 times as often as in a recipe, sesame 4.1 times, peanuts 2.9 times and tree nuts 2.9 times^[1]. A warning covers cross-contact in a factory, not the recipe, so an allergen few recipes use can still be named on many packs.

Fish, sulphites, gluten and milk go the other way: more records list them in the recipe than in a warning. Milk is in 192,782 recipes and 74,440 warnings, a ratio of 0.4.

What does “may contain” mean, and is it required?

It means the allergen could be present through cross-contact, such as a shared line or factory, and it is not an ingredient. The line is voluntary in the EU, the UK and the US, and no legal threshold triggers it, so one factory may print it while another with the same risk does not^[2]^[3].

The UK Food Standards Agency asks businesses to use it only after a real risk assessment, never as a blanket disclaimer^[3]. So its absence does not prove the allergen is absent.

Bravoora’s guide to reading a label for allergens sets out where the line sits on a pack in each market^[4].

Which words does a “may contain” line use?

More than one phrase. Bravoora’s label checker reads twelve English phrases as a precautionary line, among them “may contain”, “may also contain”, “traces of” and “may be present”, and, for the factory, “manufactured in a facility”, “produced in a facility” and “made in a facility”. Whatever the wording, the allergen after it is a warning, not an ingredient.

What else do the warning counts show?

Across the 14 allergens, the traces field holds 622,476 mentions and the allergens field 615,374; one record can name several allergens in each^[1].
Milk has the lowest ratio, 0.4: it is named in 192,782 recipes and 74,440 warnings^[1].
Eggs sit closest to even: 54,783 recipes and 56,374 warnings, a ratio of 1.0^[1].

Method: the allergens and traces fields of the Open Food Facts export of 4,535,553 products, read on 13 October 2026^[1]. A record counts once for each allergen a field names. The fields are filled in by contributors from the pack, so a product without them may still carry a warning, and the counts compare one field with the other rather than measure every pack on sale. Contains information from Open Food Facts, which is made available here under the Open Database License (ODbL)^[5].

Which words on a label are a precautionary line?

May contain, may also contain, may contain traces of: the usual wording.
Made in a facility that also handles, produced in a facility, manufactured on equipment: the same warning, about the factory.
Packed on a line, packed in a facility: the warning about the packing line.
Contains: a summary of the allergens in the recipe, not a warning.
Gluten-free: a claim with its own rules, not a statement about cross-contact; read the list anyway.

How do you read a “may contain” line in 30 seconds?

Read the ingredient list and the “Contains” line first: that is what is in the recipe.
Then find the warning, often in small print after the list.
Treat every allergen it names as possible, especially tree nuts, peanuts, sesame and lupin.
For an allergy, give the warning the same weight as the list; for a preference, it is your call.
Paste the label into the label checker: it marks warnings apart from ingredients.

How does Bravoora read a “may contain” line?

Bravoora reads the warning as its own sentence and keeps it apart from the ingredient list. For Mia, whose profile avoids peanuts, peanut in the list gives “Not for Mia”, and peanut only in a “may contain” line gives “Heads up”, with the printed words shown. A profile says how strict to be, and the answer follows it. The methodology shows how it is tested.

Let Bravoora read the label with you.

Tell it once what matters: your allergens, your diet, the ingredients you watch. Every answer then shows the words it is based on.

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Scope and limits

This article compares two fields of Open Food Facts, a database its contributors fill in from real packs: it covers the records that fill them in, not every product on sale.

Rules covered: the voluntary “may contain” line in the EU, the UK and the US. Sources were checked on the dates listed below.

This is general label information, not medical advice. With a diagnosed allergy, ask your clinician how to treat a “may contain” line.

Frequently asked questions

Is “may contain” required by law?

No. It is voluntary in the EU, the UK and the US, and no legal threshold triggers it. It should follow a real risk assessment, but its absence does not prove the allergen is absent.

Which allergen do “may contain” lines name most?

Tree nuts: Open Food Facts records them in the “may contain” field of 117,647 products, against 41,106 that list them in the recipe.

Is “may contain” the same as “contains”?

No. “Contains” sums up the allergens in the recipe; “may contain” warns of possible cross-contact. For an allergy, a “may contain” line deserves the same weight as “contains”; Bravoora shows the two apart.

Why do lupin and sesame warnings outnumber recipes so far?

A warning covers cross-contact in a factory, not the recipe, so an allergen few recipes use can still be named on many packs. Lupin is named in 8,534 warnings and 1,196 recipes, sesame in 48,128 warnings and 11,789 recipes.