Australians are increasingly being hospitalised for severe and life-threatening allergic reactions, known as anaphylaxis, researchers from the Murdoch Childrens Research Institute in Melbourne have found.

Researchers analysed 14 years of hospital data to 2012, extracting admissions for anaphylaxis. Anaphylaxis admission rates increased by 50% over this period, they found. Rates increased rapidly in the final half of the period, with 5.6 people per 100,000 hospitalised with food anaphylaxis in 2005, compared with 8.2 by 2012.

It revealed an urgent need to research and implement strategies thought to prevent food allergies from developing, and to prevent those with allergies from being exposed to triggers, the study published on Wednesday in the Journal of Allergy and Clinical Immunology concluded.

A co-author of the study, Professor Mimi Tang, said the researchers also found the most rapid growth in admission rates came from the five to 14-year-old age group, which had increased 110% by 2012. One in every five hospital admissions in this age group was to treat anaphylaxis.

“This is concerning to us because this older childhood adolescent period is associated with a greater risk of fatality for anaphylaxis,” Tang said.

“We have previously looked at deaths from anaphylaxis, and this previous research tells us adolescents and young adults under 35 are the groups where deaths occur.”

Food allergies have been steadily increasing in developed countries over the past 20 years, with a number of theories as to why, including environmental and lifestyle factors. Australia has some of the the highest food allergy rates in the world, affecting around one in 20 children and two in 100 adults, the Australasian Society of Clinical Immunology and Allergy says.

Anaphylaxis is the most severe form of allergic reaction and is treated as a medical emergency, with symptoms including hives, swelling of the face, lips and eyes, and vomiting.

Tang said it was not certain why these severe reactions were increasing.

“We could conjecture that teenagers and young adults are eating out and not preparing their own food, while when they were younger, their food environment would have been more highly controlled by their parents,” she said.

“As they get older, they may be a bit more careless or nonchalant about their allergies.”

People should not assume that carrying an anaphylaxis “pen”, which delivers a shot of adrenaline to the bloodstream to help open up airways and assist breathing, would protect them.

“It is not a fail-safe option,” she said. “Some people don’t carry them, and in a small number of cases the pen does not work and does not prevent death.”

Those caring for children, including teachers, must be well trained to recognise symptoms of a reaction, she said.

There should be a focus on other ways of managing allergies, such as avoiding restaurants and other high-risk environments where a reaction was more likely to occur, she said.

The were a number of factors thought to be contributing to an increasing number of people suffering from allergies, Tang said.

“In the past we were exposed to a broad range of good bugs pivotal to intestinal microbiota in the gut, and which are understood to play a critical role in early life immune programming,” she said.

“Over the last half century, there has been been a change in this environmental exposure; the breadth of bugs we are exposed to now is more narrow.”



Researchers also believe there is a critical period between four and 11 months of age where potentially triggering foods, such as peanuts, could be safely introduced to the diet to maximise the chance of building tolerance.

Previous studies had also found that the further people lived from the equator, the higher allergy rates are, leading researchers to believe vitamin D also played a role in protecting against allergy development, Tang said.