Childhood allergies are more common than ever.

Childhood allergies are more common than ever.

'We have never been so busy,'' says Susan Prescott, an immunologist at a children's hospital in Western Australia. ''I arrive to see the allergy clinic waiting room as overcrowded as usual. Brimming with children, some scared, some screaming, some just bored. All with serious allergies. Our lists are so long that many have been waiting over a year for their appointment.''

Welcome to the world of an allergy specialist. Prescott is also the author of The Allergy Epidemic, a new book on the rise - and rise - of allergies in Western societies. Eighty years ago, Prescott's grandmother was a doctor who practised at a time when antibiotics had become the cavalry, rescuing children from life-threatening infections. Now, the granddaughter works with children whose immune systems are under attack, not from germs but from modern lifestyles - but there is no cavalry to fix the problem.

''A new Melbourne study has shown that one in 10 Australian children has a food allergy,'' Prescott says. ''In the past decade there's been a fourfold increase in emergency department visits with life-threatening anaphylactic reactions. But although people are focused on the foods children are allergic to, the real problem is changes to our environment that are affecting the immune system.''

The hygiene hypothesis is the theory that our clean, modern environments deprive young immune systems of early exposure to the microbes that help them to develop, making children more vulnerable to allergies and autoimmune diseases such as Type 1 diabetes. But exposure to germs from animals and not-so-clean surroundings may not be as important as exposure to other bugs - the ones living in our gut. The gut is home to millions of immune cells, and the kind of bugs that inhabit our gut in early childhood may influence how well our immune systems develop, Prescott says.

Which brings us to another possible piece in the allergy puzzle: prebiotics. This is the soluble fibre in our diet that also acts as fodder for some of the gut bacteria that help us stay healthy. But in refined Western diets, fibre is in short supply.

''Prebiotics are found naturally in breast milk and studies have found that adding prebiotics to milk formula reduces the risk of babies developing allergies,'' Prescott says.

Our dodgy balance of dietary fats may be another culprit. Our intake of omega-6 fats (in products such as vegetable oils and margarines) is more than 20 times that of our intake of omega-3s (from foods like fish), resulting in women having low levels of omega-3 fats in pregnancy and in their breast milk, Prescott says, and this may contribute to inflammatory diseases such as allergies.

''The best advice we can give at this stage is, don't smoke in pregnancy - we know it affects the immune system and the developing lungs of the foetus - and breastfeed if possible. A fish oil supplement in pregnancy may help, too.''

The Allergy Epidemic: A Mystery of Modern Life (UWA Publishing, $29.95) is out now. All proceeds go to allergy research.

Fact file ...

❏ One in 10 children has a food allergy.

❏ Cases of life-threatening anaphylactic reactions have risen fourfold in a decade.

❏ Low levels of omega-3 fats in pregnancy and low fibre intake may contribute to allergies in children.