20-30% of the population are susceptible to allergies. This tendency runs in families, however, not all those with a tendency actually suffer allergy problems.

An allergic reaction can show itself in different ways, such as sneezing, an itching or runny nose, skin rashes, breathing problems, and coughing.

By far the most common allergic illness in the UK is hayfever from grass pollen. This commonly causes itching, sneezing, and a runny or blocked nose. Other problems can include sore eyes, an itchy palate and breathing problems.

Hayfever can be a real nuisance, itching and sneezing can also make it difficult to work or study properly. Most hayfever sufferers find that they feel much better if they regularly use hayfever treatments, such as nose sprays and tablets. Consult a local GP or pharmacist for advice on suitable treatment.

Allergy can often cause asthma, a common lung disease which can make breathing difficult, and gives a tight feeling in the chest. Asthma affects people of any age, although it is most often found in the young and middle-aged. Asthma may be set off by a year-round allergen such as house dust mites, or by a seasonal one, such as pollen. Advise should be sought from your GP if your asthma is being triggered by allergens.

Some allergies are easier to diagnose than others. For example, hayfever or asthma which gets worse in June and July is very likely to be due to an allergy to grass pollen. With other allergies, such as house dust mite or animal fur, special tests may be required to determine the problem. A GP may refer a sufferer of a lung allergy to a lung specialist.

It is difficult to avoid pollens, the most common cause of allergic illness. It may help to wear sunglasses, and to keep windows shut, especially when in cars and tall buildings. Avoid open grassy spaces, particularly during the evening or at night, when there is more pollen at ground level. A holiday by the sea, or abroad, during the peak pollen season may help. If a bad allergic problem is caused by cats or dogs, then it is better not to keep such pets.

If this is not possible, then keep the animal out of doors as much as possible, and keep the house very clean. Washing a cat or dog once a week is also an effective way of reducing allergen levels in the home. To reduce house mite problems, use special covers for mattresses, pillows and duvets. Clean the house often, as carefully as possible, and allow plenty of air in - this helps to reduce the dampness that house dust mites like. It helps to use a good vacuum cleaner, fitted with a small pore-size filter.

Long-term or recurrent treatment will almost certainly be needed. If the condition is particularly severe a course of desenitisation may be advised. Occasionally long-term corticosteroid injections may be offered.

The only way to stop the symptoms from worsening is to avoid the allergen where possible - this is often, however, impractical.

Occasionally people grow out of allergies although this is not usual.