Young, better-off boys are most at risk from killer allergy

Young boys from affluent backgrounds are more likely to suffer from a peanut allergy than other children, a study by researchers in Scotland has shown.

The research, by a team at the University of Edinburgh, found that young boys have higher rates of the condition than young girls and children from well-off homes are more likely to be affected than those from poorer backgrounds.

But so far it remains unclear why nut allergies are common in boys and the better off, leading the scientists to call for more research to explain the trends.

Peanut allergies commonly cause breathing problems and, at their most serious, can trigger life-threatening anaphylactic shock.

The new findings, published in the Journal of Allergy and Clinical Immunology, emerged from the health records of more than 400 GP practices in England between 2001 and 2005.

They showed that boys younger than 20 are almost a third more vulnerable to peanut allergies than girls in the same age group.

However, the pattern reverses in adulthood with slightly more women than men being at risk.

Part of the reason may be that after the age of 15 women are more likely to visit their doctor and therefore have the allergic condition detected, the researchers said.

Another possibility is that biological changes linked to sex hormones around the time of puberty might influence immune system-driven allergic reactions.

The highest rates of peanut allergy were found in children between the ages of five and nine.

The research suggests more than 25,000 people in England have been diagnosed with a peanut allergy at some point in their lives, a lower figure than previous estimates which suggested it may affect up to 1 per cent of the population.

It is not yet clear whether fewer people are actually being affected or whether the change is due to under-recording of cases by GPs.

Dr Daniel Kotz, who led the Department of Health-funded study, said: "Having a serious allergy like this can cause great anxiety and stress to those affected.

"We now need more research to help explain why the condition occurs relatively more often in boys and affluent people."

Dr Colin Simpson, another researcher on the project, said they would like to do further work in Scotland to try to work out accurate numbers of people affected by food allergies.

He said the higher rates in more well-off people may be due to this group being more likely to go to their GP to be diagnosed.

"It could be that the more affluent are coming to their GPs, or there could be a biological explanation for this," Dr Simpson said. "For instance, they talk about the hygiene hypothesis - an idea that over-clean living causes allergic disease."