Australians have some of the highest food allergy rates in the world. Why are they on the rise — and what are we discovering about their causes, diagnosis and treatment?
With an estimated 161,000 Australians now diagnosed with a food allergy, you probably know a work colleague who can’t eat peanuts, a family member allergic to seafood, or a friend’s child who reacts to eggs. For some it can lead to life-threatening reactions, while for others it’s less serious — but it can still be life-changing. Here’s the very latest science.
Food allergies 101
A food allergy occurs when your body develops an immune response to food. The most common triggers are egg, cow’s milk, peanuts, tree nuts, seafood, sesame, soy, fish and wheat. Food allergy symptoms flare up almost as soon as the allergic person consumes the allergen — but to be classed an allergy, the same reaction must occur each time. Symptoms include anything from rashes around the mouth, hives, difficulty breathing, or in the worst case, life-threatening anaphylaxis.
Food allergies affect approximately 10 per cent of babies under 12 months. Some allergies can be outgrown — egg and milk allergies usually disappear by the age of five. Allergies to nuts, fish and sesame, however, are typically lifelong.
Interestingly, allergies seem to be lingering longer now than they used to. “In our clinical experience, we used to see the majority of food allergies outgrown by primary-school age, but now it’s often not until high-school age”, says Sharon Trueman, Dietitian at Sydney’s Royal Prince Alfred Hospital Allergy Unit.
Allergies on the rise
Worldwide, food allergies have been increasing over the past 20–30 years. Over the last 10 years, hospitalisations in Australia due to anaphylaxis have doubled — but the jury’s still out on why there has been a rapid rise in the prevalence of food allergies.
Typically, allergy diagnosis is highest in children, but increasing numbers of teens and young adults are also now being diagnosed.
“The biggest challenge these days is that we rarely see a single food allergy any more,” says allergy specialist dietitian Anna Richards.
“Most presentations are now for multiple and complicated food allergies.”
The ‘hygiene hypothesis’ and the role of gut bacteria is a potential reason for the increase in allergies. This theory suggests we’re losing important immune responses because of our ‘clean’ modern lifestyle. This could be placing infants at increased risk of allergies, because it limits their exposure to microbes. Changes to food processing techniques, too, and the late introduction of allergens to children, could also be fueling the allergy explosion.
THE LATEST SCIENCE
Many interesting developments have occurred in the allergy research fi eld, which is changing how some allergies are diagnosed and treated.
GUT MICROBIOME
Recently, the role of gut bacteria in influencing our genes — through interactions between genes and environment — has come under the research spotlight. Some experts are now promoting a more targeted approach to hygiene that encourages a diverse range of ‘good’ bacteria, while minimising harm from disease-forming bacteria.
In 2018 researchers investigated the gut microbiota of children aged 16–36 months who then developed an allergy to eggs. They uncovered differences in the balance of gut bacteria between children with, and children without, food allergies. They even found gut bacteria differences between children with allergies and those with intolerances. Based on such research, a possible future treatment could be to alter the gut bacteria of allergy sufferers to make it similar to that of people who don’t have allergies.
VITAMIN D
The potential link between a pregnant women’s vitamin D levels and her child’s food allergy risk is another exciting area of research. Australian researchers found babies who were vitamin D deficient were three times more likely to have an egg allergy, and up to 11 times more likely to be allergic to peanuts. However, the protective effects of vitamin D may vary between ethnic groups.
GENE TESTING
Global research on allergies and genetic markers has let allergy specialists build a portfolio of genes to ‘test for’ when diagnosing food allergies. Studies of twins suggest that 80 per cent of the risk for food allergies is inheritable — but there are still many questions regarding the role of genetics.
In 2017, one of the world’s largest studies into genetic causes of food allergies identified five different gene locations suspected to be involved in these allergies. As risk factors become clearer, the potential for prevention and more targeted treatment of food allergies increases.
How to introduce allergy foods
Recently, the advice about introducing allergy foods to babies as part of weaning has changed. It’s now recognised that introducing foods, such as egg and peanuts, to infants earlier can increase their tolerances to such foods.
The Australasian Society of Clinical Immunology and Allergy recommends introducing solids, including allergens, to infants at about six months of age.
By 12 months, all common allergens should be introduced — postponing this can actually increase the risk of a food allergy developing.
When introducing allergens, you should start with a very small amount, such as a quarter of a teaspoon of smooth peanut butter, and gradually build up.
Once an allergen has been introduced, it’s very important to continue including it in the infant's diet in order to maintain tolerance.
If you suspect an allergy
If you think you or your child has a food allergy, seek medical advice. Your doctor may perform a RAST test — a blood test that measures IgE antibodies. Most commonly, however, doctors will prick your skin to allow a small amount of the allergen to enter. If a swollen, irritated lump appears at the site of the skin prick, that’s a sign that the allergen is a trigger.
“It gets quite complicated, because it’s not just a matter of doing a skin prick or blood test,” Trueman says. “All of your clinical and medical history has to be considered, as well as the timing of when you had the food. It’s important that you see an allergist or immunologist who can interpret this altogether.”
5 TIPS FOR HANDLING A NEW ALLERGY
one
See a dietitian about how to avoid the food allergen.
two
Discuss potential nutrient deficiencies with your dietitian.
three
Make appropriate food substitutions to meet your dietary needs.
four
See your doctor or dietitian to learn the signs and symptoms of allergen exposure.
five
If necessary, develop an action plan for handling anaphylaxis events with your doctor.
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WHERE FOOD INTOLERANCES FIT IN
The terms food allergy and intolerance are often used interchangeably, but are very different conditions. Instead of involving the immune system, a food intolerance is triggered by compounds in food that irritate nerve endings. Food intolerances aren’t life-threatening. People with them can often tolerate small amounts of a particular food, but large quantities pose a problem. Threshold levels vary for each person.
Some common triggers of food intolerance are:
● NATURAL FOOD CHEMICALS — salicylates, amines and glutamates
● ADDITIVES — natural or artificial colours and
preservatives
● LACTOSE — the natural sugar that's found in milk
● FRUCTOSE — the natural sugar found in fruit, honey and table sugar.
Food intolerance symptoms include headaches, migraines, asthma, sweating, palpitations and skin reactions. Whereas symptoms caused by food allergies are often immediate, food intolerance symptoms sometimes take 12–24 hours to fully develop.
COELIAC DISEASE: WHAT IS IT?
Often incorrectly labelled an allergy or intolerance, coeliac disease is in fact an autoimmune condition. It’s where the body has an abnormal reaction to gluten — a protein found in wheat, rye, barley and oats. Over time, repeated exposure to gluten inflames the bowel lining. This reduces the body’s ability to absorb nutrients and can lead to conditions like osteoporosis and anaemia. The only known treatment for coeliac disease is to follow a strict, lifelong gluten-free diet.
In "Australian Healthy Food Guide", February, 2019, excerpts pp.31-35. Digitized, adapted and illustrated to be posted by Leopoldo Costa.
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