food allergy

A generation ago, a child with an allergy was virtually unheard of. These days it’s almost impossible to find a kindergarten, preschool, coffee group or playgroup that doesn’t have a child with an allergy.

For more and more children, food is becoming a cause of sickness. Worldwide the number of children developing food allergies is dramatically rising and it seems there is no one single cause. So what’s behind the rise, who is being affected and what can we do to protect our children from developing food allergies?

What is food allergy?

The term ‘allergy’ is often misused to describe annoying symptoms such as bloating after drinking a cup of milk. As a result, many people think they have a food allergy when it is, in fact, an intolerance. There is also a widespread belief that food allergies are trivial when, in fact, they are frightening and can be life-threatening.

A food allergy is an immune system over-response to a food protein and the body triggers an allergic reaction. Symptoms can include hives, itching, swelling, vomiting, diarrhoea and nausea. In some cases, it can cause potentially life-threatening symptoms, called anaphylaxis, either by breathing difficulties and/or a sudden drop in blood pressure.

Sometimes food allergy may be less obvious and can be characterised by infantile colic, reflux of stomach contents, eczema, chronic diarrhoea, and failure to thrive. Recent studies have found that up to 40-50 per cent of eczema cases in young children are triggered by food allergy.

On the rise

According to Associate Professor, Rohan Ameratunga, a clinical immunologist at Auckland Hospital, there has been a significant increase in allergies in the last 20 to 30 years. This rise has mirrored the rise of other allergic diseases – asthma, hay fever and eczema - around the world.

It is estimated that between 5-8% of children have a food allergy - that’s about one in 15 children!

In children, the most common allergies are to cow’s milk and egg, followed by soy, peanuts, tree nuts and wheat. The majority of children will lose their allergies by age three to five years. But allergies to peanuts, tree nuts, fish and shell fish are generally prolonged, which is why these four allergies are the most common amongst adolescents and adults.

Any food protein can cause an allergic reaction. Dr Ameratunga says we are seeing different food allergies emerging due to migration and changes in our diet: “Sesame seed allergy, for example, is an emerging problem in both Australia and New Zealand, probably due to the fact we are eating more Middle Eastern foods. There is also a cultural variation where we see rice as a main allergy in Japan.”

Several theories have attempted to explain the rise in food allergies and one leading theory is the ‘hygiene hypothesis’. This theory suggests that exposure to certain germs and infections early in life are important in training the immune system to recognise foreign threats to our body. Our tendency to lead a lifestyle of cleanliness and hygiene means our children don’t get exposed to these ‘good bugs’ and their immune systems have become over-reactive.

Another explanation for the rise in food allergy is the introduction of foods too early in an infant’s development before the immune system is mature enough to handle them. This could occur through the allergenic food passing through breast milk or an unintended exposure in life through highly processed foods typical of the Western diet with some foods containing hidden sources of the allergy-causing food.

Food can be fatal

Food allergy is the leading cause of anaphylaxis (a life-threatening allergic reaction) outside of a hospital setting, and the foods most often implicated are peanuts, tree nuts and shell fish.

“It has double the incidence and three times the mortality of anaphylactic reaction to bee stings,” says Dr Ameratunga.

Each year about 125 people die in the USA, and in Australia there have been five recent deaths from food allergy.

 “Although we don’t have any studies here, we estimate there are one to two deaths every one to two years in New Zealand,” says Dr Ameratunga.

While 90 per cent of anaphylactic reactions occur in preschool children, the majority of deaths occur in adolescents. “Asthma is a big risk factor for fatality and most people actually die from an asthma attack,” he says. “Those who have died usually have not been giving adrenaline or it wasn’t used early enough.”

While it is rare to die from anaphylaxis, anaphylaxis itself is not rare. An Australian study found that at least one in 170 schoolchildren has had an anaphylactic reaction.

Treatment and prevention

Although there is no cure yet for food allergy, research in the last decade has increased exponentially and researchers are getting much closer to developing a vaccine. They are also looking at changing the way the immune system responds to allergens through desensitisation - this works much the same way as allergy shots work for hay fever.
But until this comes into fruition, avoiding the allergenic food is the only treatment. Most importantly is that if you suspect your child has a food allergy, you should see an experienced GP or allergy specialist.

Once a diagnosis has been made, either through a skin prick test or a blood test in conjunction with a detailed history, parents and their children will have to be taught how to read food labels to appropriately avoid the food they are allergic to, how to recognise early symptoms of a reaction and how to treat it.

There is no proven way to prevent allergies but there are a number of steps that may reduce the risk including exclusive breastfeeding for the first six months, delaying the introduction of solids to age six months, and avoiding exposing your baby to cigarette smoke.

Food labels

Going to the supermarket takes on a whole new meaning when you are avoiding common foods. You need to learn to read food labels and prepare more foods from scratch that you may have before. And every time you buy, you will need to read every label every time – manufacturers change their ingredients or processing aids from time to time!

Since December 2002, New Zealand’s food labelling laws require that the most common allergenic foods be stated on food labels. This includes milk, egg, soy, peanut, tree nut, sesame, fish, shellfish and gluten-containing cereals, including wheat.
While it is not mandatory for manufacturers to include precautionary statements such as ‘may contain traces of peanuts’, these are usually only used if the manufacturer feels there is a significant risk of cross contamination; for example, if biscuits containing peanuts are produced on the same line as another biscuit.

Written by Allergy New Zealand

As printed in Littlies Parenting Magazine, Issue 41, May 2007. www.littlies.co.nz.