Half of people who think they have a food allergy do not – study

By Nicola Davis

The number of adults who think they have a food allergy is almost double the figure who actually have one, research has revealed.

While the study was conducted in the US, experts say a similar situation is also seen in other countries, including the UK. The researchers found that many people with an allergy do not have a prescription for potentially life-saving medication, while others might be avoiding foods unnecessarily.

The study suggests almost 11% of adults in the US have a food allergy, equating to more than 26 million people. About 12 million of these are estimated to have developed the allergy as an adult, highlighting that allergies do not only begin in childhood.

“This is really concerning because chances are they could eat the food and then all of a sudden they have a reaction to a food that they could previously tolerate – so what changed in their environment or in them that caused them to now develop this food allergy?” said Ruchi Gupta, a professor of paediatrics at Northwestern University and a co-author of the research.

“Some of these foods you know that they probably were able to eat [previously] because they are such common foods in the diet, but shellfish was interesting – it could be one that they are trying for the first time as an adult.”

Gideon Lack, a professor of paediatric allergy at King’s College London, who was not involved in the research, said the growing problem of food allergies in adults might be linked to the dramatic rise seen in children over the past 20 years.

“We have been focusing efforts and concerns about food allergy in children, and this study is telling us there is a very significant burden of food-allergic disease in adults and we ought to be directing more attention and resources towards diagnosing and treating those adults,” he said.

Writing in the journal Jama Network Open, researchers in the US describe how they conducted a survey in two groups of participants between October 2015 and September 2016. In total more than 40,000 adults in the US took part.

Participants were asked if they had a food allergy and were questioned about their reactions and diagnoses. The team then assessed whether the reported allergy, whether diagnosed or not, was “convincing” – for example if the participant had experienced symptoms such as throat tightening or vomiting.

“If they only had, say, bloating or stomach pain or diarrhoea then we took them out because that could be a lactose intolerance or a food intolerance,” said Gupta.

The results reveal that the most common “convincing” allergy was to shellfish, affecting 2.9% of adults, with milk and peanuts in second and third place, affecting 1.9% and 1.8% of adults respectively.

But while 10.8% of participants were deemed to have at least one convincing food allergy, almost twice as many – 19% – reported they had such a problem.

“There are so many adults out there who have a negative reaction to a food. It is really important to get a proper diagnosis so that they can really know is this something treatable like lactose intolerance, or is this a life-threatening food allergy that they need to be very careful with,” said Gupta.

Of those with a “convincing” allergy, almost half said they had developed at least one of their food allergies as an adult, while about 38% said they had undertaken an emergency hospital visit as a result of a food allergy. However, only 48% said they had received a diagnosis from a doctor and just a quarter said they had a prescription for adrenaline, a common allergy treatment.

Prof Clare Mills, an expert in food allergies at the University of Manchester, welcomed the study but said it had limitations, including relying on self-reported data, including for symptoms. What’s more, she said, the healthcare system in the US is very different to the UK, meaning access to healthcare, and even the way adrenaline is prescribed, is very different.

Stephen Till, a professor of allergy at King’s College London, said the prevalence of “true” allergies seen in the study seemed surprisingly high, but the widespread misapprehension of having an allergy chimed with his clinical experience in the UK.

“I often see patients who think that they have a severe allergy who either aren’t allergic or who have mild allergy. They may have been unnecessarily prescribed adrenaline auto-injectors and be on a restricted diet avoiding even trace exposure to the suspected culprit,” he said, noting that this could cause significant anxiety and difficulties.

“Unfortunately … we have a shortage of physicians who are trained in adult allergy and so this amplifies these kinds of problems.”