The allergy epidemic

Allergic diseases, including eczema, asthma, hay fever and food allergies, affect about 30 to 40 per cent of the world’s population and, according to the World Allergy Organisation, it’s children who bear the “greatest burden of this epidemic”.

While there is no one clear cause for the high allergy rates, contributing factors include environmental pollutants, dietary changes and increased hygiene, says Dr Susan Prescott, a Perth-based specialist in childhood allergy and immunology and author of The Allergy Epidemic – A Mystery of Modern Life.

And nowhere is this more evident than Australia. “We have the highest levels of allergies in the world,” Prescott says. “In the last decade, Australia has seen a five-fold rise in serious (and potentially life-threatening) food allergies in preschoolers.”

An ongoing study by the Melbourne Children’s Research Institute, titled ‘HealthNuts’, has found that one in 10 one-year-olds has an allergic reaction to foods. Unlike food intolerance, which is an enzyme reaction, food allergy is an immunological reaction to a protein or substance in the environment and symptoms can vary from being mild (rash or skin swelling) to potentially life-threatening (known as anaphylactic).

Prescott says that while rates in childhood asthma and hay fever have been high for decades, it is this recent “second wave” of food allergies that is alarming. She says 90 per cent of food allergies are caused by hen’s eggs, cow’s milk, soy, tree nuts, peanuts, wheat, shellfish and fish, and while children tend to grow out of some, others (like nuts and shellfish) are more persistent.

“This generation has caught us by surprise and we are seeing that many of the most common food allergies, such as egg and milk, are tending to persist a bit longer than they used to as well,” she says. “So we are not just seeing a rise in the rate of disease and the severity, but it is also becoming more persistent.”

Possible causes

While the exact cause of this sudden spike in childhood allergies is unknown, research points to a number of contributing lifestyle and environmental factors, including increased hygiene, environmental pollutants, reduced sunlight exposure (as a result of increased screen time), genetics and modern dietary patterns (with children consuming less fresh fruit, vegies, and foods containing omega-3 fats and dietary fibre).

We really have to understand what it is about our modern environment and lifestyle that is driving this process because it’s just too quick to be genetic [alone],” Prescott says.

“We are progressively eating less fresh fruit and veg, and more processed food, and our intake of saturated fats has increased while omega-3 consumption has decreased.”

Compared with previous generations, Prescott says our modern diet also includes less dietary fibre, a natural anti-inflammatory which helps to promote favourable bacteria in the gut. (See ‘Complementary Strategies’ for more on diet.)

While some influencing factors, such as family history, are unavoidable, there are steps we can take to help reduce the risks of childhood allergies. Overall, Prescott says it’s a commonsense approach, including: “Not smoking during pregnancy or around children; breastfeeding, where possible, for at least six months; minimising exposure to chemicals and toxins; and eating a healthy balanced diet.” (See ‘Reducing the risks’ box for more.)

While the adverse effects of cigarette smoke and traffic exhaust are well known, Prescott says the effects of other pollutants, such as pesticides, are less understood: “Progressive industrialisation has led to many new environmental chemicals that did not exist in traditional societies, including many products of industry and agriculture. These persistent organic pollutants (POPs) contaminate our food and water supplies.

“Though they may only be consumed in trace amounts, these POPs (such as pesticides) accumulate in our body fat over our lifetime, and levels can amplify with each generation. Many POPs have been detected in maternal fat, umbilical cord blood and breast milk; clear evidence that babies are exposed to these during critical times of development.”

Ongoing research

Other factors, such as prebiotics in the diet, may have a role to play in reducing the risks of allergy, but research is ongoing. And unlike previous recommendations, Prescott says avoiding the introduction of certain foods (such as egg, milk, nuts and seafood) to babies over six months to try to reduce the chance of allergy is no longer advised. In fact, avoidance of these foods has been associated with increased (rather than decreased) risk of allergic disease and possibly coeliac disease.

The HealthNuts study, which involves over 5,000 children, found that even sunshine levels may play a role in children developing food allergy and eczema, and that siblings and pets may reduce the likelihood of egg allergy in infants.

“It’s telling us that our immune systems are very vulnerable to modern environmental changes,” Prescott says. “In essence, we have disturbed the natural balance of our environment and we are now experiencing the impact on our own health.”

But, according to Prescott, herein may also lie part of the answer: “While there is not a simple one-size-fits-all solution, there is hope. The very fact that allergies have risen so much tells us that our immune system has a plasticity to it.

“We can harness that same plasticity to restore the balance and help solve the problem.”