Natasha’s Law requires retailers to display full ingredient and allergen labelling on all food made on premises and pre-packed for direct sale.
It follows the death of 15-year-old Natasha Ednan-Laperouse, from Fulham, who suffered anaphylaxis after eating a baguette which contained sesame seeds.
Parents Tanya and Nadim Ednan-Laperouse, of west London, said “Natasha would be very proud” of the change.
The pair set up the Natasha Allergy Research Foundation and launched their campaign after Natasha’s inquest highlighted a food labelling loophole that left her unaware of the hidden seeds she was allergic to.
Mr Ednan-Laperouse said the new law brings greater transparency to customers and is vital to protect the two to three million people in the UK living with food allergies.
“It is about saving lives and marks a major milestone in our campaign to support people in this country with food allergies,” he added.
“It will give people with food allergies confidence when they are buying pre-packaged food for direct sale such as sandwiches and salads. Everyone should be able to consume food safely.”
Natasha died in July 2016 after eating a Pret artichoke, olive and tapenade baguette before boarding a flight at Heathrow airport to Nice with her father and best friend Bethany.
The baguette had sesame seeds, to which Natasha was severely allergic, baked into the dough.
Natasha suffered a severe allergic reaction within minutes of taking off and her father administered two Epi-pens delivering potentially life-saving adrenaline but they did not work.
She had multiple cardiac arrests on the flight and died later that day at a hospital in France.
The coroner concluded that Natasha would not have eaten the baguette if the seeds had been included on the label.
Mrs Ednan-Laperouse said: “Natasha was always extremely careful to check the food labels and until that terrible day in 2016 hadn’t had a severe allergic reaction for over nine years.
“Nothing can bring Natasha back, and we have to live with that reality every day, but we know in our hearts that Natasha would be very proud that a new law in her name will help to protect others.
“Natasha was a very public-spirited young woman. She wanted to make a difference so this feels like a fitting tribute to her.”
The family says there is “still so much more to do” to support those with food allergies.
They are calling for the appointing of an Allergy Tsar to champion people with allergies and ensure they receive the right support including joined up health care to prevent avoidable deaths and ill health.
Food Standards Agency chief executive Emily Miles said: “If these changes drive down the number of hospital admissions caused by food allergies, which have seen a threefold increase over the last 20 years, and prevent further tragic deaths such as Natasha‘s, that can only be a positive thing.
“I understand how difficult the past 18 months have been for food businesses, and I am grateful for the effort that so many have made to prepare for the changes and enable people to make safe decisions about the food they eat.”