Allergies: Myths and facts

Everyone's talking about food allergies. We explain the myths and facts.

Food allergy is very common

Many people will tell you they have a food allergy when often they have an intolerance. In reality, one in 20 people will develop a food allergy – often temporary – and one in 100 people will have a life threatening allergy. If you have a reaction to something in your diet, don't jump straight to a self-diagnosis; seek professional advice. Food allergy is mostly a problem for babies and young children, affecting between 6-8% of them, and usually manifests itself as eczema (an itchy skin rash).

If you're allergic to one food you'll be allergic to many

Children are usually allergic to two, three or more foods. Most recover by age four. So if you're an adult reacting to a lot of different foods, it's probably intolerance.

Allergy is an extreme form of intolerance

It's not. Allergies to food, pollens, dust mites and insect stings are caused by the stimulation of the immune system to form antibodies in our blood stream and body tissues. They can be detected by skin prick testing and blood tests. When you have symptoms that don't involve the immune system, the experts call it intolerance. The underlying physiological cause is often unclear and can't be detected by allergy testing. People with intolerances can usually tolerate a small amount of the problem food, whereas someone with an allergy must avoid the food completely.

Organic foods are non-allergenic

It's not pesticides or additives that cause people to be allergic to foods but rather the proteins (a complex molecule) in the foods. So limiting your diet to organic food is no guarantee that you'll avoid food allergies; an egg is still an egg, even if it's organically produced. The immune system recognises the protein as a potential threat, even in tiny amounts.

Allergy to wheat is increasing

A wheat allergy is relatively uncommon, rarely occurs beyond infancy and reactions are usually mild. Most people who avoid wheat and other gluten-containing grains (rye, barley and oats) have an intolerance rather than an allergy. Some have a condition known as coeliac disease, where the gluten can cause damage to the lining of the gut. Coeliac disease runs in families and affects about one in 100 Australians, with possibly more undiagnosed. Blood tests are available and a definite diagnosis requires a small bowel biopsy. Treating coeliac disease involves adhering to a life-long gluten-free diet to protect the gut.

Food colouring causes allergies

As the media spotlight turns again to how additives affect us, it looks like colouring falls into the category of intolerance rather than allergy, which can make it harder to pin down. Chemical additives used in food processing, such as colours, flavours and preservatives, can cause irritation of the skin, gut and behaviour in sensitive people. Interestingly, even more frequent and insidious are the problems some people have with reactions to naturally occurring characteristic flavours (salicylates, amines and glutamates) in food. Diagnosis can be tricky, requiring elimination followed by systematic challenging to find the chemical culprit.

Allergies are caused by a weak immune system

Allergy is an immune over-reaction to substances that ordinarily pose no threat. It's a bit like calling in a SWAT team to answer a simple knock at the door. The immune system goes into action and a flood of chemicals are released that causes the discomfort of an allergic reaction. Don't consider taking any of the myriad of supplements that are marketed to boost or strengthen your immune system because they won't work.

Allergies are nothing to worry about

Some allergies to foods, drugs and insect stings can be potentially life-threatening with between 10 and 20 deaths in Australia every year. Beyond that, allergies can have a significant impact on your quality of life. Less severe food allergy can involve uncomfortable symptoms such as colic, diarrhoea, an itchy rash around the mouth, hives or eczema. And hay fever can interfere with your sleep and make you feel tired throughout the day, more irritable and unable to think clearly.

The most common food allergy is to nuts

Though peanut allergy is increasing, children can be allergic to a variety of specific foods, including eggs, milk, soy, wheat, seafood, peanut, tree nuts and sesame. Egg is the most common food allergy, but nuts are associated with the more severe reactions. Even very small amounts can provoke a reaction, often within minutes of exposure. Most children outgrow food allergies by the age of four, but nut and seafood allergies tend to persist into adulthood.

Milk intolerance is common in adults

Most children outgrow a milk allergy and can safely reintroduce dairy products into their diet. Some children and adults, however, have symptoms that can be attributed to milk intolerance, which is caused by lactose, a sugar found in all animal milks, including breast milk. Our gut is lined with lactase, an enzyme that digests lactose. If there's not enough lactase, the gut can't digest milk and it causes discomfort and diarrhoea. Occasionally,  lactose intolerance causes muscle pain, headaches, fatigue and constipation. A bout of gastroenteritis can temporarily strip your gut of lactase, causing people to be lactose intolerant for several weeks afterwards.

Allergies are on the rise

The Australasian Society of Clinical Immunology and Allergy (ASCIA) reports there has been almost a doubling of allergic disease in Western ountries over the past 25 years. Many different things, like dust mites, pollen, foods, hairy animals, insect stings and mould, can cause allergic reactions. In young children, food is the most common cause of severe allergy. There has been a dramatic increase in peanut allergies, with one in 50 children suffering and one in 200 adults. Doctors and researchers aren't exactly sure why.

Most allergies can't be cured

Although immunotherapy (desensitisation), by injection or oral drops, is available for hay fever and asthma where there are severe, difficult to manage symptoms, this is not a treatment option for food allergy. Food allergy is managed by complete avoidance of the offending food. Birth to two years is an important time in the development of the immune system and an opportunity to reduce the risk of allergy in later life. If allergies run in your family, delay the introduction of the allergic foods and maintain a nut- and seafood-free household in early years.

First published: Jun 2008

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