The number of children admitted to a hospital in England with a severe allergic reaction has been increasing every year for the last five years.
NHS figures show that 1,746 children were treated for anaphylactic shock in 2018-19, up from 1,015 in 2013-14.
Natasha Ednan-Laperuz's parents, who died in 2016 after eating sesame-containing baguette, called the increase "deeply alarming".
Scientists say environmental factors may be responsible for more allergies.
When adults with severe allergic reactions treated in hospital were included, the numbers rose from 4,107 cases to 5,497 over five years.
Children under 10 were most likely affected by anaphylaxis, with 1,018 admitted to hospital last year – compared to 601 in 2013-14.
Anaphylaxis is a severe allergic reaction that can be life-threatening.
The most common causes of serious allergic reactions are foods such as nuts, fish and shells, but they can also be triggered by wasps and bees stings, medicines and dairy products.
Even the slightest exposure to one of these allergens can be sufficient to trigger an anaphylactic reaction and bring on breathing difficulties, rapid heartbeat and loss of consciousness.
The increase in allergies is not thought to be simply because society is becoming more aware of them and better able to diagnose them.
Instead, scientists believe that factors such as changes in diet, exposure to microbes and pollution can play a role in growth – especially for the western lifestyle.
Natasha's mother, Tania Ednan-Laperuz, said: "These frightening numbers show that we are facing an emergency in the event of an allergy.
"The number of children with allergies and suffering from serious allergic reactions is increasing year by year at a deeply disturbing rate."
Hassan Arshad, a professor of allergy and clinical immunology at the University of Southampton, said the numbers confirm "a worrying increase in severe food allergy".
"We should not forget that behind each of these numbers is a child or an adult who has suffered the most severe consequences of anaphylactic shock," he said.
Fifteen-year-old Natasha had a severe and fatal allergic reaction to artichoke, olive and tapenade baguette, purchased from Pret a Manger.
She was allergic to sesame seeds but this was not stated on the product label.
Despite her father, Nadim, administering two injections of Epipen, Natasha died in hospital for several hours.
Natasha's parents have campaigned for a change in the law to require manufacturers of pre-packaged foods to list all of their ingredients. This law will come into force in 2021.
Until now, residency products and restaurants only had to notify customers if they contained the 14 most dangerous allergens – including peanuts, eggs and milk.
Natasha's parents also founded the Natasha Allergy Research Foundation, with the ultimate goal of finding a cure for allergies.