Research has shown that the number of people diagnosed with a food allergy in England has more than doubled in a decade and a third of people with life-threatening reactions do not carry an adrenaline pen.

Experts from Imperial College London analyzed GP medical records of seven million people. They found that the number of new cases of food allergies rose from 76 per 100,000 people in 2008 to 160 per 100,000 people in 2018. The overall prevalence rose from 0.4% to 1.1% over the 10-year period.

The highest prevalence of food allergies was observed in children under five years of age, with 4% affected. Among children aged five to nine, the figure was 2.4%, among 10 to 14-year-olds 2%, among 15 to 19-year-olds 1.7% and among adults aged 20 and above 0.7% in 2018, the data showed.

The rise in cases in England is likely to be seen across the UK, the researchers said. They also noted that one in three patients who had previously experienced anaphylaxis – a life-threatening allergic reaction – did not have their own adrenaline auto-injector (AAI).

The results were published in the journal Lancet Public Health.

Lead researcher Dr Paul Turner, professor of paediatric allergy at Imperial College’s National Heart and Lung Institute, said the findings showed there was an “urgent need” to “better support GPs and primary care staff” in caring for patients with food allergies.

“A food allergy can have a huge impact on people’s lives and, in some tragic cases, even shorten their lives,” he said.

Food allergies occur when the immune system overreacts to certain foods, such as cow’s milk, peanuts, eggs or shellfish. In severe cases, they can lead to anaphylaxis, which can cause swelling of the airways, difficulty breathing and cardiac arrest.

The study did not examine why the number of cases rose so sharply, but experts said there were likely many different factors behind the increase. For example, increased awareness of food allergies probably led to more people seeking help on the NHS.

Parents who followed outdated advice not to give their babies certain foods until they were older were also likely to blame, experts said. If a child is not allowed to eat peanuts, contact with dust, furniture or creams containing peanut oil could trigger a reaction in their immune system.

The increasing use of cleansers, creams and body lotions may also play a role, as they can destroy the skin barrier, experts say. This allows food to enter the immune system through the skin rather than the gut, increasing the risk of food allergies.

Poor nutrition, genetic predisposition, vitamin D deficiency, environmental pollution and other factors have also previously been cited as possible explanations for the increasing number of cases.

Imperial said that while more doctors diagnosed food allergies during the decade studied, the number of new cases may be declining. It is unclear why the number of newly diagnosed food allergy cases may be stagnating, they said.

One possibility is changes in infant nutrition guidelines that no longer recommend delaying the introduction of foods such as peanuts into a child’s diet, Imperial said. For children at higher risk for food allergies, earlier introduction of eggs and peanuts is now a standard recommendation.

Turner said the study “paints an important, albeit mixed, picture of food allergy in the UK”.

He added: “The good news is that while the number of new cases each year has increased, the prevalence of food allergies has remained stagnant. However, more than a third of patients at risk of severe reactions do not carry potentially life-saving adrenaline auto-injectors such as EpiPens.”

Prescription of AAIs – devices given to people at risk of anaphylaxis – was also less common in poorer areas of the country, the researchers found. Only 55% of adults and 64% of children who had previously experienced anaphylaxis had been prescribed AAIs.

Nadim Ednan-Laperouse, co-founder of the Natasha Allergy Research Foundation, said: “It is shocking and alarming that over a third of people who have experienced anaphylaxis – the worst allergic reaction – have not been prescribed an adrenaline auto-injector. And the poorest in society are even less likely to be prescribed this life-saving medication.

“This is completely unacceptable and inevitably puts lives at risk. Anyone suffering from a severe food allergy should carry two AAIs at all times.”