what is an allergy?

Some people refer to having an allergy, others a sensitivity and others intolerance. Below is an explanation of what each of these terms mean.

Allergy - an allergy is an over-reaction of the body's immune system caused by irritant substances known as allergens. The body mistakenly recognises the allergen to be a threat and reacts by releasing a chemical or “antibody” called immunoglobulin E (IgE) to attack the invading allergen. This leads to blood cells releasing other chemicals, eg histamine, that produce the signs and symptoms of an allergic reaction.

One of the most common questions is whether or not you or your child will grow out of an allergy. The simple answer is that there are no guarantees, but a significant proportion of children who develop allergies do grow out of them. Some, however, will have to learn to control their allergies into adulthood and throughout their lives.

Some allergies are genetic, meaning that they may run in families. If at least one parent suffers with eczema, asthma or allergies, it is more likely that any children will also suffer one or more of these. It seems that the immune system of people who are predisposed to allergies has a greater tendency to produce IgE antibodies. The numbers of people suffering with allergies in the Western world seems to be increasing. In fact, it is estimated that 1 in 3* adults will develop an allergy at some time!

Sensitivity - a sensitivity is an exaggeration of a normal side effect produced by contact with a substance. For example, the caffeine in coffee may cause symptoms such as a headache in some people but not in others.

Intolerance - an intolerance is where a substance, such as lactose, causes unpleasant symptoms (such as diarrhoea) for a variety of reasons, but does not involve the immune system. People intolerant to certain foods can often eat a small amount without experiencing any problems. Whereas, people with a food allergy will have a bad reaction even if they come into contact with a tiny amount of the food they are allergic to.

* According to the British Allergy Foundation

For further information about the different types of allergies follow this link

Information written by the talkhealth medical panel

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Last Reviewed: 19 November 2010
Next Review Date: 19 November 2012