[chjohasbrouck]

Is this possible? It doesn't seem like the necessary information is captured in a picture.

I don't think there's a person that could tell you whether food in a picture has allergens, let alone an app.

[zitterbewegung]

Yes you are right. The app works by identifying the dish and then searching in an ingredient database. If the dish looks visually the same to one with peanuts then the app would have a false negative .