A 15-year-old girl died after eating a Pret A Manger sandwich that failed to list an ingredient to which she was allergic.
Natasha Ednan-Laperouse died in 2016 after eating a baguette that had sesame seeds.
An inquest heard that Pret A Manger received nine complaints of sesame-related allergy incidents in 2015, but still failed to list sesame as an ingredient.
The chain now lists all allergens, including sesame, in its products.
Pret A Manger ignored nine warnings that its baguettes could cause deadly allergic reactions until a 15-year-old girl died after eating one of its sandwiches, an inquest has heard.
Natasha Ednan-Laperouse, who suffered from numerous allergies, suffered a cardiac arrest and died after eating an artichoke, olive, and tapenade baguette in July 2016, the BBC reported on Wednesday.
The baguette contained sesame, to which Ednan-Laperouse was allergic but was not labelled in the allergen ingredients.
Ednan-Laperouse, from London, bought the sandwich at Heathrow Airport before flying to Nice on summer holiday, the BBC said.
She collapsed about 20 minutes into the flight, suffered a cardiac arrest, and died within hours.
Her father, Nadim Ednan-Laperouse, said his daughter foamed at the mouth and said she couldn't breathe, according to Sky News. The symptoms persisted despite Nadim's administering two EpiPen shots to Natasha and a doctor's carrying out CPR for the rest of the plane ride.
Nadim Ednan-Laperouse said in a statement cited by the BBC: "I was stunned that a big food company like Pret could mislabel a sandwich and this could cause my daughter to die."
Inquests in the UK aim to determine the cause of a person's death, but do not attribute responsibility of the death.
Ednan-Laperouse was not the only person who was allergic to unlabeled ingredients in Pret A Manger's products.
The global food chain received nine complaints of sesame-related allergy incidents in the year before Ednan-Laperouse died, the inquest heard, according to the BBC.
One of the cases involved a woman nearly dying after suffering an anaphylactic shock from a baguette in 2015, the BBC reported. Her family warned Pret A Manger about the ingredients, but the chain still failed to label its sandwiches with allergy information.
The chain now lists all its allergens, including sesame, in its products, ITV News reported.
A Pret A Manger spokeswoman told Business Insider in a statement: "We were deeply saddened to hear about Natasha's tragic death, and our heartfelt thoughts are with her family and friends. We take food allergies and how allergen information is provided to our customers extremely seriously."
Jonathan Perkins, the company's director of risk and compliance, was quoted by 5 News as saying: "I accept that a number of individuals have had a negative experience, even a tragic experience, but thousands of customers and allergy sufferers shop with us safely."
Earlier this year British advertising regulators banned Pret A Manger from claiming its food is "natural" because the chain uses additives in its products.