How to read allergen labels on food (EU, UK and US)

Updated 29 October 2026 · By IngrediLens

Allergen labels follow different rules depending on where the food was sold. If you know the three or four places allergens can appear on a pack, you can check a product quickly. You also need to know where the law stops.

The short version

• EU and UK: allergens are part of the ingredients list and must be emphasised, usually in bold. There is no "Contains" box in the law.
• US: allergens are named either inside the ingredient list, for example "whey (milk)", or in a "Contains:" line right after it.
• Everywhere: "may contain" and "made in a factory that also handles…" statements are voluntary and follow no fixed wording. See what "may contain" really means.

EU and UK labels: look for the emphasis

Under Regulation (EU) No 1169/2011, which the UK kept in its own law, 14 allergens and their derivatives must be shown in the ingredients list whenever they are used. The typeface has to set them apart from the other ingredients. Most brands use bold. Capitals, underlining or a different colour are also allowed.

Example: Ingredients: Water, wheat flour, sugar, egg, rapeseed oil, emulsifier (soya lecithin), salt.

A few points matter in practice:

• The allergen is named with the ingredient that comes from it, for example "casein (milk)" or "modified starch (wheat)". The source name is the part you check, not the technical name.
• If a food has no ingredients list (some drinks, for example), the label must say "Contains" followed by the allergen.
• Food sold loose or in restaurants must also give allergen information. This can be spoken, as long as it is accurate and available.
• In the UK, food prepacked for direct sale (sandwiches made and packed on site, for example) must carry a full ingredient list with allergens emphasised. This is the rule known as Natasha's Law, in force since 1 October 2021.

The full list is in the 14 EU allergens.

US labels: ingredient list or "Contains"

The Food Allergen Labeling and Consumer Protection Act (FALCPA) and the FASTER Act set nine major food allergens: milk, egg, fish, crustacean shellfish, tree nuts, peanuts, wheat, soybeans and sesame (since 1 January 2023). Each one in a product must be named at least once, in one of two ways:

1. In the ingredient list, in plain words or in parentheses: "whey (milk)", "flour (wheat)", "lecithin (soy)".
2. In a "Contains" statement directly after or next to the ingredient list: "Contains: wheat, milk, soy."

The specific tree nut (almond, cashew…), fish (cod, salmon…) or crustacean (shrimp, crab…) must be named. Highly refined oils made from an allergen are exempt. Molluscs, mustard, celery and lupin are not US major allergens, so a US "Contains" line will not warn you about them. More in the 9 major US allergens.

A 6-step routine for every pack

1. Read the full ingredient list, not just the front. "Free from" claims and pictures are marketing. The ingredient list is the legal information.
2. Look for your allergen's source name, in bold (EU/UK) or in parentheses or the "Contains" line (US).
3. Check for other names. Allergens can hide behind technical words such as casein, albumen, semolina or tahini. Our guides list them for milk, egg, gluten, soy and nuts.
4. Read the precautionary statement ("may contain", "not suitable for…"). Decide with your allergist how strictly to treat it.
5. Check where the product was made and sold. An imported product may follow the rules of another country, and a sticker translation may be incomplete.
6. Repeat next time. Recipes change. A product that was fine last month may now use a different supplier.

Where labels fall short

• Lists are not complete. Any food can cause an allergy. If your allergen is not on the legal list (kiwi or pea, for example), it is only shown as a normal ingredient, without emphasis, and may be hidden inside "flavourings" or "spices".
• Cross-contact warnings are voluntary. A product without "may contain" can still carry traces.
• Labels can be wrong. Food agencies publish allergy alerts and recalls when an allergen is missing from the label. The FSA in the UK and the FDA in the US both list them on their websites.

How IngrediLens helps

IngrediLens reads the ingredient list with your iPhone camera, from a photo, from typed text or by barcode. It highlights the allergens you chose, including their other names and "may contain" statements. It reads labels in English, Spanish, Portuguese, German, French and Italian, so an imported pack is easier to check. Your filters stay on your device and you don't need an account. The app can miss things, especially on blurry or curved labels, so treat it as a second pair of eyes and always read the pack yourself.