Natasha Ednan-Laperouse, 15, collapsed on board a flight in July 2016 after eating an artichoke, olive and tapenade baguette she had bought at a Pret outlet in Heathrow Airport.
Her family have called for a change in food labelling laws after an inquest confirmed that the teenager from Fulham, south-west London, had had an allergic reaction to sesame in the sandwich.
Pret has now announced that full ingredient labelling will be introduced to all products that are freshly made in its shop kitchens, and labels will list all ingredients, including allergens.
The company said it will start trialling full ingredient labelling on product packaging from next month, rolling it out to all UK shops as quickly as possible.
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Clive Schlee, Pret chief executive, said: “I want to say again how deeply sorry we are for the loss of Natasha. I said we would learn from this tragedy and ensure meaningful changes happen.
“I hope these measures set us on course to drive change in the industry so people with allergies are as protected and informed as possible. Nothing is more important to Pret right now.”