Food intolerance

Food intolerance refers to any adverse reaction to food or food additives. Food allergy is only one such reaction and refers specifically to food intolerance in which the body's immune (defence) system is directly involved.

Some doctors prefer to use the term food intolerance only for adverse reactions to food in which the body's immune system is not involved (non-immune or non-allergic).

There are different types of non-immune reactions to food. The most obvious example is simple toxicity. Contaminants (substances which get into food during the growth, harvesting, processing, packaging or storage of food) are occasionally harmful. In severe cases these contaminants can make food poisonous and anyone eating them will suffer ill effects. Much less obvious are the adverse reactions of a few people who lack the enzymes necessary to digest certain foods.

A common example is lactose intolerance. This is due to the lack of the enzyme lactose, which is essential for the digestion of the milk sugar lactose. Most people have adequate levels of the necessary enzyme and tolerate milk.

Another example of non-allergic food intolerance is the reaction caused by naturally occurring chemicals in food, or by food additives (chemical reaction). These reactions are similar to true allergic responses and may be mistakenly labelled as food allergy.

Food additives include a variety of substances, such as preservatives, flavouring agents, colouring agents, etc. Well-known examples are tartrazine, monosodium glutamate (MSG), sulphur dioxide and benzoates. Chemical reactions to food or food additives are not true allergic reactions because they do not involve the immune system.

Another interesting cause of a non-allergic reaction is psychological reactions to foods. It has been shown that if one is convinced, perhaps by a past experience, that one cannot tolerate a certain food, one tends to avoid it. Should one eat it again in the future, the chances are that one will experience, that one cannot tolerate a certain food, one tends to avoid it.

Should one eat it again in the future, the chances are that one will experience ill effects.

Is true food allergy common?

True food allergy is less common than popularly believed. It is estimated that only between 1% and 4% of the general population suffers from a definite food allergy. Food allergy tends to be more common in children (up to 6%) than adults. In selected groups, such as children with eczema, the prevalence of food allergy may be as high as 25%.

What are the symptoms of food allergy?

The symptoms of food allergy may be confined to the digestive system only (the most common sort), or involve other parts of the body as well.