Allergen word list updates: how AllergenLens re-checks your saved scans

The word list is the heart of AllergenLens. It holds the names an allergen can hide under on a label, from plain words to other names and E-numbers, across the label languages the app reads. Each release can add names or remove ones that caused confusion. This post explains how those changes reach your results and how to see what changed.

A word list that stays on your iPhone

The list is stored in the app and never leaves your iPhone. There is no download in the background and no server to ask, so a label is checked the same way in airplane mode as at home. The flip side is that the list only changes when you update AllergenLens from the App Store.

You can see which list you have in Settings › About, under Allergen word list, with the version, for example v4. Label languages shows which languages the list covers. For how the list deals with E-numbers and words that could mean more than one thing, see E-numbers and unclear words.

What happens after an update

The first time you open a new version, AllergenLens reads every kept scan again with the new list. This runs in the background, once per version, using the text already stored with each scan. No new photo is needed.

If the new list reads a scan differently, that scan gets a Result changed tag in History, or on the Scan tab for your latest scan. The tag stays until you open the scan. At the top of the result you'll then see a note such as Result changed with word list v4 (was v3), with lines like:

Under that: The allergen word list was updated. The result below uses the new list.

No longer matched is worth a careful look. It means a word that used to count is no longer on the list, usually because it was matching something it shouldn't. It isn't a sign that the allergen is absent, and Not found in the text we read is never a guarantee. Read the pack.

What's new in the word list

What's new in the word list in Settings shows the version you have and the one before it, then the number of Terms added and Terms removed. Under By allergen, each allergen lists examples of names added (+) and removed (−), with a count. The page ends with how many terms the list now holds.

On a fresh install there is nothing to compare yet, so the page says this is the first word list on this iPhone and how many terms it has.

Which version checked a result

Every result is worked out again when you open it, so the findings always use today's list. At the bottom of a result, a line says Checked with allergen word list v4., followed by the version used when you scanned, or Word list at scan time: not recorded. for older scans.

Saved snapshots carry the version they were made with, and so does a missed allergen report, so anyone reading it knows which list was used. This is separate from a recipe change: when you re-scan a product, the old text is read with today's list first, so recipe change alerts only show differences on the pack.

If the word list can't be used

If the list fails to load, AllergenLens doesn't guess. The Scan tab shows Scanning is paused with a Try again button, and any result opened in that state says nothing on the label was checked. Earlier Result changed tags are kept as they were.

The app also runs a quick self-test on the list. If it doesn't pass, results still show what was found, but are headed Can't confirm, check the label yourself, because the app can't confirm that an allergen isn't there. Updating or reinstalling AllergenLens usually fixes this; your profiles and scans stay on the iPhone. If it keeps happening, contact support.

FAQ

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