Treatment usually means removing foods and reintroducing them one at a time, over months. It is a long process where what fails is the record-keeping, not the willpower.
A log with the date of every meal and every symptom. When it is time to decide whether a food came back in well, the answer is written down instead of half-remembered.
Milk, wheat, egg or soy turn up in places nobody expects. You look up a food or a dish and see what it contains before eating it.
A profile for them in the same account, and each phone in the house chooses whether to receive their alerts. Every alert carries their name in front, so nobody acts on the wrong person.