Search on to solve anaphylaxis puzzle

Tamara Hunter

Unravelling the mystery of anaphylaxis and why it affects some people and not others could take decades, says a Perth scientist who has been given a $260,000 research grant to investigate the life-threatening allergic reaction.

Simon Brown, an emergency physician at Royal Perth Hospital and researcher with the WA Institute of Medical Research, has begun what he expects to be years of painstaking research to find out what is happening in the cells during an anaphylactic reaction.

He wants to know why even a tiny exposure to an allergen can cause a rapid, body-wide response in some people, and little or no reaction in others.

"What we're trying to do is work out why in some people does the gun go off," Professor Brown says. "What is it that links the trigger, the antibody, to that generalised response, with the gunpowder going off?

"There are people with huge levels of allergic antibodies, yet when they get stung all they get is a local reaction - they don't get a systemic reaction.

"Some people with very large amounts of antibody and who are clearly allergic just don't have a reaction, whereas others do."

Pinpointing the process is a tricky business and requires samples taken from people in the midst of anaphylaxis. That means capturing them as they arrive at the RPH emergency department.

"We have a system whereby if someone comes in with anaphylaxis, as the IV goes in we take a quick set of research bloods," Professor Brown says.

"We do it again an hour later and before they go home so it's part of the routine of care." Consent is sought later, with the samples being discarded if people decline to take part in the research.

He says the unique and exploratory nature of the work, which brings basic laboratory research to the bedside in the resuscitation room, probably helped win him the grant from the American agency, the Food Allergy and Anaphylaxis Network.

By figuring out how anaphlyaxis works at a molecular level, researchers hope to stop it occurring and learn how to improve immunotherapy for those with existing conditions.

"It's about how do you prevent it and once people have it how do you stop them having further reactions? A key to working out how to do that is understanding the quintessential nature of anaphylaxis.

"It's complex and it could be a couple of decades until we get an answer. The problem is it's much like trying to find a species of mushroom in the Amazon."

Professor Brown says that although there is no doubt anaphylaxis and food allergy have become a big public health burden and are straining resources, he questions whether diagnosis in all cases is based on comprehensive clinical examination and testing.

"While it's very important for people who have it, and there does seem to be some evidence that it's increasing, there are a lot of anxious parents around who've been told their child is allergic to something on the basis of tests which mean nothing," he says.

"There are a lot of people going around who have had minor reactions, or worse, one of these snake-oil salesman type tests that tell you you're allergic to something."

He says that although studies show hospital admissions for anaphylaxis are increasing, the data is not always reliable. There could be several reasons why more people are being admitted - for example, greater awareness of the problem or, in some cases, incorrect diagnosis.

"The way the diagnosis is applied by clinical staff can sometimes be inaccurate - it might just be a bit of a rash and it's 'anaphylaxis'. It's very hard to tell from the data what is really happening."

Studies also show that although admissions are increasing, death rates have not changed.

"You can interpret that in two ways - one way is that this is actually a bit of a problem with the admission data. Or it means we are doing a damned good job and we are admitting them and therefore preventing deaths despite this big increase in presentations.

"It's really hard to know what the truth of the matter is."

He says it's also important to note that death in children from anaphylaxis is rare.

"Parents worry a lot about allergy, but deaths in young children from allergy are so rare. The risk is very low. There are two peaks for deaths from allergy.

"There's a very small peak in food allergy and that tends to be in adolescents and young adults.

"But the far bigger peak occurs later on as people get older. Most deaths from anaphylaxis occur in adults, particularly older adults and particularly medication related, from drug allergy and insect venom allergy. It's all a matter of perspective."

Despite uncertainty about the data, Professor Brown says there is a clear need for better access to high-quality allergy services and timely follow-up when people have anaphylactic reactions.

"Just because people aren't dying often from a disease doesn't mean it's not a huge burden and a cost to society. Food allergy might not cause death often but it can contribute to asthma severity, obesity, exercise intolerance.

"There's a whole lot of things clustered around allergy which have a big disease burden."