A bit about food allergy and intolerance

Some foods cause adverse reactions in susceptible people. The best-known example of a food intolerance is lactose (milk sugar) intolerance. Up to ten per cent of northern Europeans suffer from lactose intolerance.

How reactions develop

The first time you eat a potentially allergenic food, you do not usually have symptoms, but your immune system mistakenly prepares to protect you against it. The next time you eat that food you release chemicals that cause symptoms such as eczema or life-threatening anaphylaxis.Food allergies usually begin in childhood and may be lifelong. However, some allergies, such as milk allergy, may be outgrown.

People with a food intolerance are not able to digest or process specific foods properly in the body, resulting in bloating, abdominal pain, wind, vomiting, or diarrhoea. The problem usually involves a defect or deficiency in an enzyme necessary to digest some foods. Unlike food allergies, intolerances are usually not dangerous.

Symptoms of a food allergy

These range from a tingling in the mouth, eczema, hives, vomiting, abdominal cramps, and diarrhoea to swelling of the tongue and throat, breathing difficulties, and a drop in blood pressure. Symptoms typically appear within minutes to two hours after eating a suspect food.

Food allergies are common in people who are susceptible to eczema, hay fever (allergic rhinitis), or asthma.

Allergy history

It is estimated that five to eight per cent of all children may develop a food allergy by the age of two years, although studies suggest that babies with a family history of allergies may be two to four times more likely to develop an allergy or intolerance.

Since infancy is an especially vulnerable time for food allergies to develop, allergy prevention efforts must be started immediately after birth to be effective. Compared to babies fed cow's or soya milk formula, babies who are exclusively breast-fed for a prolonged period develop less eczema and wheezing in the first year of life.

Assess your child's risk for allergies

Do you have a history of allergies (such as a food allergy, allergic eczema, hay fever, asthma, or allergy to furry animals, pollens, dust mites, or mould)?
Does your spouse have a history of allergies?
Do your children have any allergies?

Skin-prick test

In this test for allergy, a drop of a common allergen (a substance that can cause an allergic reaction) is placed on the skin, which is then punctured with a small needle. If the skin reacts to the allergen by producing a weal, or hive, the test result is positive.

A positive result should be followed with a diet that eliminates the suspected food and followed later by a food challenge, in which the food is reintroduced to see if symptoms return. Food challenge tests must be medically supervised as they may trigger anaphylaxis.

Lisa Hark, PhD RD & Dr Darwin Deen

Posted 30.06.2010

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