Allergen overdose

Skin prick tests can be used to determine what types of allergies you have. Image: Alexander Raths/Shutterstock

Over the past 20 years, allergies have grown steadily in Australia. Some researchers believe that it is because our immune system doesn’t fight against as many diseases as it use to. Are we killing ourselves with cleanliness? Emma Bastian reports.

Allergies can range from inconvenient to life threatening, but a 2011 study showed that allergies might actually protect you from cancer. Brown University scientists discovered that people with higher levels of immunoglobulin E (IgE) antibodies, which are produced in response to allergies, in their blood were less likely to develop gliomas (a type of brain tumour). If gliomas develop, they were more likely to survive longer if the IgE levels in their blood were higher.

Australia has the highest rate of childhood allergies in the world with 1 in 10 children suffering a food allergy. This is a sharp increase in the last 20 years and it seems to keep rising, although doctors and researchers cannot quite explain why. “It’s going up steeply with no end in sight and the reasons are not understood,” said Dr Robert Loblay, Director of the Allergy Unit in the Royal Prince Alfred Hospital in a statement. This is also not just an Australian trend — last year it was reported in the Journal of Allergy and Clinical Immunology that one in thirteen children in the US have a food allergy.

While there is no doubt that there has been a rapid increase in allergies worldwide, the National Institute of Health found that we aren’t actually as allergic as we think we are. Apparently between five to eight per cent of people have a food allergy but 30 per cent of people believe they have a food allergy.

Many studies have suggested that allergies can develop as early as in the womb. A study published in the Journal of Physiology found that mothers whose diets were rich in polyunsaturated fatty acids (PUFAs) gave birth to babies with improved gut immunity and therefore had less chance of developing food allergies.

Clean enough for you?
Cleanliness is not next to godliness; it just gives rise to different diseases. Epidemiologists, medical professionals and health researchers now believe that allergies and other autoimmune diseases might have spiked so rapidly in the last few decades because we aren’t diseased enough. The hygiene hypothesis purports that we have become too clean and disease free — with less infections to fight against, the immune system has taken to attacking harmless things instead.

The hygiene hypothesis took shape after it was noted that children in large families were less likely to have allergies than one-child families, presumably because children with siblings are exposed to the siblings’ diseases and infections (remember chickenpox?). Larger epidemiological studies have shown that urban-dwelling children have higher rates of allergies than rural-dwelling children. And on a global scale, allergies are far less common in third world countries and rapidly rising in the western world.

Climate change and allergies
While the hygiene hypothesis does go some way to helping explain the rise in allergies around the world, it doesn’t explain it completely — especially the increase in asthma sufferers, who generally inherit their allergy.

Since the 1960s there has been a decrease in the number of hospital admissions for asthma treatment, presumably because asthma awareness, management and treatment has improved. However in the same period there has been an increase in the number of hospital admissions for severe asthma attacks.

“The rise of asthma and other allergic diseases such as food allergies has been a global phenomenon”, says Paul Beggs, associate professor at Macquarie University in Sydney, who studies the link between climate change and the rise in allergies. Beggs believes that “the hygiene hypothesis does not fully explain the global increases in asthma that occurred over the latter decades of the last century. I therefore think that the hygiene hypothesis were and are acting in combination”.

Recent studies have linked climate change to the change in allergen levels. Jacqueline Mohan from Duke University in the US has shown that increased levels of atmospheric CO2 not only increased the amount of plant growth, it also increases the allergencity of plants such as ragweed pollen (a common culprit of hayfever). Another study showed similar findings with poison ivy grown at elevated CO2 levels. Allergens in plants can be found within the seed storage or as part of the plants’ defence system, which means they are quite susceptible to changes in environmental conditions.

Climate change isn’t just affecting plant allergies; the increase in temperatures and earlier onset of seasons has meant an increase in range of insects and exposing people with insect allergies who may not have previously encountered them. Dr Jeffrey Demain studied insect reactions in Alaska over 1992 and 2007 and found a four-fold increase in insect-caused allergic reactions.

Despite our best efforts to remain disease free, perhaps our bodies are meant to have a level of infection in order to keep fighting fit, especially in these changing times.

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