The onslaught of allergies

One of the major problems with treating allergy is that when we talk about ‘allergy sufferers’, we don’t necessarily have a clear cut idea of who it is we’re talking about. In 1997, the National Health Interview Survey in the US changed the way it reported asthma, resulting in a situation where estimates for prevalence (the percentage of the population with asthma) became very difficult to compare to pre-1996 estimates. It became almost impossible to say for sure whether prevalence had significantly risen or fallen.

The problem of diagnosis is one that plagues health professionals in many fields and it has wreaked considerable havoc among allergy specialists. Earlier this year, the University of New South Wales published research that suggested many children reportedly suffering from peanut allergies had been misdiagnosed. Only two thirds of children supposedly testing positive for peanut allergy using standard ‘prick tests’ – where tiny amounts of allergen are introduced into the skin – actually reacted when they were given peanuts to eat. Bryan Wainstein, the lead author of the study, says, “There is a population of children who have never eaten peanuts – or worse, those that eat them everyday, then have a positive peanut skin test and are told not to eat them.”

But peanut allergies in particular remain a cause for concern, and especially where children are involved. One school in Concord, Massachusetts, has introduced a strict ‘No Nuts’ policy which bans anyone from bringing foods containing nuts onto the campus, encouraging parents elsewhere to demand that their schools follow this lead.

This may appear to be a no holes solution, but it will only prevent a handful of severe allergic reactions and in fact, this kind of approach can actually exacerbate the allergy problem.

Because so many foods contain trace elements of peanuts – they are found in cakes and biscuits simply because they pass through the same factories en route to our kitchen cupboards - it is virtually impossible to eliminate them totally from the western diet of processed foods. However, the problem arises because research suggests that it is negligible amounts of nut protein that prime the immune system for hypersensitivity. In other words, ‘removing’ nuts from schools and homes could reduce the amount of allergen to exactly the right levels to trigger allergies. In the UK, the government has previously discouraged new parents from feeding their children nuts in order to combat rising food allergies. This may have had the opposite effect to the one intended.

But it is thought that an allergy doesn’t develop as a result of environmental influences alone; genetic predispositions are undoubtedly also to blame. Last month, researchers at the University of Southern California reported finding two genes that they say could be responsible for increasing the risk of asthma. However, these genes seemed to require a kind of environmental switch. Children with suspect genetic backgrounds were much more likely to be asthmatic if they lived closer to major travel routes and were therefore exposed to higher levels of pollution. “This finding demonstrates the critical role of gene environment interaction,” says David Schwartz, director of the National Institute of Environmental Health Sciences.

Are we living in a more allergic world?