Food allergies and intolerances

CHOICE investigates why nut allergy rates are now soaring, and what you can do if you think you have an allergy.
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Food allergies and intolerances

In brief

Nut allergies are growing at a faster rate than any other kind of food allergy, raising concerns about exposure to nuts for high-risk young children.
Testing is available for food allergy and intolerance, but be wary of those not conducted by a GP, allergy specialist or paediatrician – some appear no more reliable than reading tea leaves.

Australia has one of the highest allergy rates in the world, and the number of people affected is growing at an astonishing rate. The number of children aged under five ending up in hospital with a life-threatening allergic reaction (anaphylaxis) increased fivefold in the decade to 2007.

According to experts, the explosion is a relatively new phenomenon. “The allergy wave hit 10 to 15 years ago. It’s an epidemic … and it’s growing exponentially – we’re swamped,” says Dr Rob Loblay, head of Royal Prince Alfred Hospital’s (RPAH) allergy clinic in Sydney.

But it’s not every type of food allergy that’s skyrocketing. Data from childcare centres in the ACT and Central Sydney Area Health Service shows while allergies to proteins in milk, eggs and seafood have remained steady, peanut allergies increased by 50% between 2003 and 2006, and cashew allergies, while less common overall, increased a staggering five times.

Please note: this information was current as of March 2009 but is still a useful guide today.

Why are nut intolerances increasing now?

There are a number of theories, all as yet unproven, which might explain the increase. It could be related to Western lifestyles – as countries become more developed and prosperous, allergy rates increase.

According to Dr Andrew Kemp, Professor of Paediatric Allergy at Childrens’ Hospital Westmead, Sydney, one explanation suggests a relationship between allergies and exposure to bacteria through soil and animals; people living on farms are less affected than those in cities and towns. And experts such as microbiologist and immunologist Dr Mary Ruebush, author of the book Why Dirt is Good, argue that our modern dirt phobia means children’s immune systems don’t get the opportunity to develop properly, and this could play a part in this very modern problem.

Other possible explanations include the timing of introduction of solids to babies, changes in food processing and the mother’s diet during pregnancy. Dr Anne Swain, Chief Allergy Dietitian at RPAH, also points to the changing consumption patterns of nuts. As the popularity, availability and affordability of a type of nut grows, she says, so do the allergy cases. “It’s peanuts and cashews now, but walnuts and macadamias look like the next wave.”

Why do kids become allergic?

You can’t be allergic to something your body has never seen – there has to be a first exposure that sensitises a susceptible person, so that the next time he or she is confronted with that foreign protein their immune defence goes into overdrive. Experts say there’s an early window for sensitisation, around two to four months of age.

So exposure to nut proteins via breast milk is one possibility. But there are other theories on the possible ways babies could be exposed, such as through smooches from dads after they’ve eaten nuts (broken skin from beard rash can allow the foreign proteins in), or through broken skin from eczema letting allergens in if there are nuts around. Nappy rash cream, which sometimes contains peanut oil, could also be a culprit, particularly as it’s often used on broken skin.

More research is needed to find out what’s really behind the trend, and a number of studies are under way. Loblay and Swain, for example, are investigating whether the risk could be reduced by minimising the likelihood of contact between baby and nut allergens during pregnancy, breastfeeding and in the first months of life. They say that while studies show changing the mother’s diet during pregnancy and breastfeeding doesn’t reduce the risk of allergy, they don’t take into account other contact with nuts.

Allergies in adulthood?

Allergies are usually discovered in childhood. Most problems in later life are likely to be intolerances. However, it is possible for adults to discover an allergy to something they’ve only recently come into contact with, such as insect stings, drugs or dust/pollen (after moving to a new environment).



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