US Allergen Labelling vs UK Allergen Labelling: Key Differences

If you sell food products online, the gap between US and UK allergen labelling law is not a minor administrative detail — it is a compliance minefield that can result in product recalls, regulatory fines, and serious harm to customers. Food business owners expanding across the Atlantic, or simply trying to serve both markets from a single Shopify store, frequently discover that what satisfies the Food Standards Agency in London does not satisfy the FDA in Washington, and vice versa. The differences go beyond which ingredients appear on a label. They touch the number of allergens recognised by law, the language required to declare them, the format of that declaration, and even the thresholds that trigger a mandatory warning.

This post breaks down the most consequential differences between FALCPA (the US Food Allergen Labelling and Consumer Protection Act) and UK allergen law as it stands post-Brexit under the Food Information to Consumers Regulation retained in UK law. You will learn which allergens each regime covers, how the "contains" statement works in each country, what cross-contamination labelling rules apply, and what practical steps you can take right now to keep your Shopify product listings compliant in both markets.

Whether you are a bakery shipping gift boxes internationally or a sauce brand preparing to list on a US marketplace, this guide gives you the legal grounding to make informed decisions — and avoid costly mistakes.

---

How Many Allergens Are Covered? The Core List Differences

The most fundamental difference between the two regimes is the number of major food allergens each one recognises. UK law mandates declaration of 14 allergens, a list inherited from EU Regulation 1169/2011 and retained post-Brexit. These are: celery, cereals containing gluten, crustaceans, eggs, fish, lupin, milk, molluscs, mustard, peanuts, sesame, soybeans, sulphur dioxide and sulphites (above 10 mg/kg), and tree nuts. The US, under FALCPA as amended by the FASTER Act of 2021, currently mandates declaration of nine major allergens: milk, eggs, fish, shellfish, tree nuts, peanuts, wheat, soybeans, and sesame.

The practical implication of this gap is significant. A product containing mustard, celery, or lupin must carry a mandatory allergen declaration on packaging sold in the UK — but a US-bound equivalent carries no such obligation under federal law. Molluscs are treated as a major allergen in the UK but are not separately listed in the US (they fall under "shellfish" in looser terms, though US shellfish labelling focuses mainly on crustaceans). If you are producing a single recipe and labelling it for both markets, you cannot simply use your UK label in the US and assume you are covered — the reverse is equally true.

Sesame is the newest addition to the US list, having been elevated to major allergen status by the FASTER Act and becoming enforceable from 1 January 2023. The UK has recognised sesame since it adopted EU rules, so this is one area where the two regimes have recently converged. If your product contains tahini, hummus, or any sesame-derived ingredient, you must now declare it under both regimes — a useful reminder that allergen law is not static, and monitoring regulatory updates is part of running a compliant food business.

---

The "Contains" Statement: Required in the US, Not in the UK

One of the clearest structural differences is the "Contains" statement. In the US, FALCPA permits food manufacturers to declare major allergens using a plain-language "Contains" statement placed immediately after or adjacent to the ingredient list. For example: "Contains: Milk, Wheat, Peanuts." This statement is optional in the sense that manufacturers may alternatively bold or capitalise the allergen name within the ingredient list itself, but if a "Contains" statement is used, it must be complete and cannot omit any of the nine major allergens present in the product.

UK law does not use a "Contains" statement in the same way. Instead, UK regulations require that allergens be emphasised within the ingredient list — typically using bold text, a different font, or a contrasting colour — so that consumers can scan the ingredient list and immediately identify allergens without hunting through dense text. There is no legal equivalent of the standalone "Contains" box in UK labelling law. Some UK manufacturers include advisory allergen summaries as a courtesy, but these are not a legal substitute for the required emphasis within the ingredient list itself.

This distinction matters practically when you are designing packaging or populating product descriptions in your Shopify store. A US-compliant label that uses a "Contains" box but does not bold allergens within the ingredient list would be non-compliant in the UK. Conversely, a UK label with beautifully bolded ingredients but no "Contains" statement would technically comply with UK law but might leave US regulators unsatisfied if the bolding is not treated as meeting FALCPA's alternative declaration method. If you are selling into both markets, your safest strategy is to bold allergens within the ingredient list and include a "Contains" statement — satisfying both regimes simultaneously.

---

Precautionary Allergen Labelling: "May Contain" Rules

Precautionary allergen labelling (PAL) — the "may contain" or "made in a facility that also processes" language — is an area of significant divergence between the two countries, and one where both regimes have notable weaknesses. In the UK, PAL is not legally mandated, but the Food Standards Agency's guidance strongly encourages its use when genuine cross-contamination risk exists. Crucially, UK guidance discourages the use of blanket "may contain" statements applied to every product regardless of actual risk, as this erodes consumer trust and makes the warnings meaningless to allergy sufferers who rely on them.

In the US, the FDA similarly does not legally require PAL statements under FALCPA. The regulation covers intentional ingredients, not adventitious contamination. However, US manufacturers use "may contain" language extensively, often driven by liability concerns rather than genuine risk assessment. The FDA has issued draft guidance indicating that PAL should be reserved for situations where shared equipment or facilities create a genuine, not merely theoretical, risk of cross-contact — a position broadly consistent with UK FSA guidance. In practice, the US food industry's use of PAL is far less disciplined, and many manufacturers apply it as a catch-all disclaimer.

For Shopify store owners, the implication is that you cannot simply copy-paste your cross-contamination disclaimers between markets. UK customers, particularly those with severe allergies, are trained to treat excessive PAL statements with scepticism — too many vague warnings and allergy sufferers will assume the product is unsafe and shop elsewhere. US customers may expect the language as standard. Tailoring your allergen copy to the audience is not just good marketing; it is part of operating responsibly in each jurisdiction.

---

Online Selling: Digital Labelling Obligations

Selling food online introduces a separate layer of complexity that is handled differently in each country. In the UK, Natasha's Law (which came into force in October 2021) primarily addresses pre-packed for direct sale (PPDS) food, but the broader FIC Regulation also requires that food sold online must provide allergen information before the purchase is completed and upon delivery. This means your Shopify product pages are legally required to display full allergen information for UK customers — not just on the physical label, but on the digital storefront itself.

In the US, FDA regulations under FALCPA apply to packaged food labels. There is no equivalent federal requirement specifically mandating that online product pages display allergen information before purchase, though the FTC's general consumer protection framework and state-level laws in places like California create indirect obligations around accurate product representation. That said, any food sold in interstate commerce must still carry a FALCPA-compliant physical label, so allergen information must reach the consumer — the question is whether it must appear on the website before checkout.

For practical compliance across both markets, the smartest approach is to treat the UK's stricter pre-purchase digital disclosure standard as your baseline for both markets. Display allergen information prominently on every product page. Tools like Allergen Matrix are built specifically to help Shopify merchants manage this — generating structured allergen tables that surface the right information to the right customer, at the right point in the purchase journey, without requiring manual updates every time a recipe changes.

---

Tree Nuts and Fish: Specificity Requirements

Both regimes require tree nut and fish declarations, but they handle specificity quite differently. Under FALCPA, if a product contains tree nuts, the label must specify which tree nut — almond, cashew, walnut, pecan, and so on. Generic "tree nuts" is not acceptable in the US. The same applies to fish: the species must be declared (e.g. "salmon," "cod," "tilapia"), not simply "fish." This specificity requirement exists because different consumers are allergic to different tree nuts or fish species, and a blanket declaration fails to give them the information they need.

UK law also requires declaration when tree nuts or fish are present, and the FSA recommends specifying the type of nut or fish where possible, but the legal text under UK FIC Regulation lists tree nuts as a category with named sub-types — almonds, hazelnuts, walnuts, cashews, and so on — all of which must be declared individually when present. This is broadly consistent with the US approach, but the mechanism differs: in the UK, the emphasis-in-ingredient-list method naturally captures the specific nut name, whereas in the US, the "Contains" statement must spell out the exact species.

Where businesses often trip up is with compound ingredients and flavourings. If your product uses a "mixed nut" flavouring or a fish sauce that contains multiple species, both US and UK law require you to trace those components and declare every allergen present. Relying on a supplier's generic ingredient declaration without verifying the specific allergen content is a compliance failure in both jurisdictions, and ingredient substitutions by suppliers without notice are a well-documented cause of allergen recalls.

---

Conclusion

The differences between US and UK allergen labelling law are real, consequential, and growing as both regimes continue to evolve. The UK covers 14 allergens to the US's nine; the mechanisms for declaration differ; online selling obligations are stricter in the UK; and the specificity required for tree nuts and fish demands careful recipe-level attention. For Shopify merchants selling across borders, the safest path is to design labelling and product page copy that satisfies both regimes simultaneously — using bolded ingredients, a "Contains" statement, and accurate species-level declarations.

Key takeaways: Know your market's allergen list. Understand whether a "Contains" statement is required or optional. Apply PAL only where genuine risk exists. Display allergen information on your digital storefront before checkout. And review your supplier ingredient declarations regularly — a supplier change can create a compliance gap overnight.

Try Allergen Matrix free at saltai.app — no credit card required.