Food allergy scanner: what it flags, and what it misses
Short answer
A food allergy scanner reads a barcode, looks the product up, and marks the allergens you selected against that product's ingredient record. It reports what the label declares. It cannot detect an allergen in the food, cannot see cross-contamination or shared equipment, and cannot know about a recipe change the database has not recorded.
The limits come first here
For a severe allergy the distance between 'the label does not list it' and 'this is safe to eat' is the entire problem, and a barcode app only ever answers the first. Anyone who tells you otherwise is selling something.
These pages exist because that distinction is worth stating plainly, not because an app closes it.
- Cross-contamination is invisible to a database record. Shared lines, shared fryers, shared scoops.
- 'May contain' and 'produced in a facility with' are voluntary in most markets and frequently missing from database entries.
- Reformulation happens without a packaging redesign, and community databases lag it.
- An incomplete record reads the same as a clean one. Absence of a flag is not evidence of absence.
- Nothing here replaces reading the packet, asking the manufacturer, or carrying prescribed medication.
What it does on every scan
You pick your allergens once during setup. From then on every scan checks the product's parsed allergen taxonomy from Open Food Facts against that list, and anything matching is marked so it is the first thing you see rather than a row you have to hunt for.
Reading the taxonomy rather than the English label text is what makes this work across markets: milk arrives as lait, leche, Milch or latte depending on the packet, and the taxonomy resolves all of them to one tag.
The allergens the underlying data covers
Open Food Facts follows the EU's 14 declarable allergens, which overlap with but are not identical to the US's nine major allergens.
- Cereals containing gluten — wheat, rye, barley, oats, spelt, kamut
- Crustaceans · molluscs · fish
- Eggs · milk
- Peanuts · other nuts (almond, hazelnut, walnut, cashew, pecan, brazil, pistachio, macadamia)
- Soybeans · sesame · celery · mustard · lupin
- Sulphur dioxide and sulphites above 10 mg/kg
Where it earns its place
- Shopping in a country whose labels you cannot read
- Screening a trolley quickly, then reading the two products that survive
- Catching allergens under names that do not look like the allergen — casein, whey, semolina, tahini
- Sharing one consistent list across everyone who shops for the household
What else the scan returns
The same scan gives a 0–100 score built on ingredient quality and processing level, flags seed oils and controversial additives, and suggests alternatives in the same category — with your allergens still applied, so a suggested swap never contains something you avoid.
Frequently asked questions
- Can an app tell me if a food is safe for my allergy?
- No app can. It can tell you what the label declares, which is useful for narrowing choices and useless as a safety guarantee. For a severe allergy, the packet and the manufacturer are the authorities, and an allergist's advice outranks both.
- Does it read 'may contain' warnings?
- Only when the database record includes them, which is inconsistent — those statements are voluntary in most markets and are among the first things missing from a community-maintained entry. Never treat their absence as meaningful.
- Which allergens can I track?
- The set Open Food Facts declares, which follows the EU's 14. You choose which of them matter to you during setup and can change the list at any time in Profile → Personal.
- What happens if the product is not in the database?
- You get told it is unknown rather than given a clean result — a missing record and a safe record must never look the same. For an unlisted product you can photograph the ingredients panel and have the text read instead, which is still reading a label rather than testing food.
Keep reading
Last updated 27 August 2026. Nothing on this page is medical advice.
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