What is AllergyLens?
AllergyLens is a free website that checks whether a food product is safe for a person with allergies. You scan a barcode, search by name, or photograph the ingredient label, and it flags anything that matches the allergy profiles you have set up, including hidden and derived allergen names.
How much does AllergyLens cost?
It is free. There is no paid tier for the core allergen check, no ads, and no sign-up. If you want to support the project you can leave a tip, but nothing here is locked behind it.
Do I need to create an account?
No. There is no account and no sign-up. You add one or more allergy profiles and start scanning. Your profiles are saved on your device, not on a server.
Where is my data stored? Is it private?
Your profiles and history are stored in your browser on your device and are never uploaded to a server. When you photograph a label, the text recognition runs on your phone and the image is not uploaded. AllergyLens does not track you or sell data. The one exception is the optional AI check: when it runs, the ingredient text (never your profiles or names) is sent to a third-party AI provider.
How does AllergyLens check a product for allergens?
It looks the barcode up in the free Open Food Facts database, with USDA FoodData Central as a fallback for US products, then matches the ingredients and allergen tags against each profile. It recognises allergens by tag, by the Contains declaration, and by ingredient keywords, including in other languages through Open Food Facts ingredient ids.
An optional AI pass can flag hidden or derived allergen names (for example whey or casein for milk) as an extra check. It only ever adds a caution and never clears one. When it runs, the ingredient text is sent to a third-party AI provider to analyse, but your profiles and names are not.
Which allergens and diets can it check?
The nine common allergens: milk, eggs, peanuts, tree nuts, soy, wheat or gluten, fish, shellfish and sesame, plus any custom ingredients you add. It also handles may-contain traces with a per-allergen strictness setting, and can check vegan, vegetarian, halal and kosher diets.
Can I check a restaurant menu?
Yes, if AI is enabled. Paste a menu or photograph one and AllergyLens flags each dish against the active profile as avoid, caution, unclear or likely OK. Restaurant menus rarely list ingredients, so it reasons from typical recipes and errs cautious, which makes it a guide, not a guarantee. Always confirm with the restaurant.
Can I share a profile with another caregiver?
Yes. From the profile menu, "Share or sync a profile" shows a QR code and a link that carry the whole profile (allergens, settings and emergency card). The other person scans the QR with their phone camera or opens the link, previews it, and adds it. No account, and nothing is uploaded to a server.
What happens if a product is not in the database?
You can photograph the ingredient label instead. AllergyLens reads the text on your phone and checks it like any other product. This is the most reliable option for a product no database knows, and you can also add the product to Open Food Facts to help other families.
Can I check for more than one person?
Yes. You can set up a profile for each family member, and every scan is evaluated against all of them at once. The active profile gets the big verdict and the others get a short per-person row, so one scan answers the question for the whole family.
Does AllergyLens work offline?
Yes. Add it to your home screen from your browser and it works offline for products you have already viewed, which are cached on your device. A live lookup of a new product needs a connection, but label photo reading works offline after the first use.
Does it work outside the United States or in other languages?
Open Food Facts is a worldwide database, so products from many countries resolve. Because AllergyLens also matches Open Food Facts ingredient ids, products labelled in other languages are still recognised when the database has parsed them. If AI is enabled, you can also photograph a foreign-language label and it will translate the ingredients to English and flag your allergens. And it generates translated allergy travel cards in several languages.
How accurate is it? Can I rely on it?
AllergyLens is a decision-support tool, not a guarantee. Product data is crowdsourced and can be incomplete or out of date, and recipes change. Always read the physical label and, for a severe or life-threatening allergy, treat AllergyLens as a helper and confirm every product yourself. It is not medical advice.
We measure this rather than assert it. The accuracy report shows how often the matcher catches a declared allergen from ingredient text alone, broken down by allergen and by label language, along with what the measurement does not cover and the bugs it found in our own code.
How do I install AllergyLens on my phone?
Open allergylens.com in your phone browser. On Android you will see an install prompt; on iPhone, tap the Share button and choose Add to Home Screen. It then opens full screen and works offline.