The unit says that, despite an exceptionally cold and wet April, some species of grass have flowered early in the South and Midlands, due to the unseasonably mild weather experienced earlier in the year.

All grass pollen counts are currently low. But assuming that the current warm, sunny, dry weather persists, the start of the grass pollen season will lead to rapid rises in pollen counts over much of the country from late May.

The lag time between the start of the pollen seasons in the South and North is likely to be only about ten days to two weeks - much shorter than average.

Grass growth

Grass growth has been very good this year with high production of pollen, so the Unit is predicting that the grass pollen season will be severe if the current weather conditions continue into the first two weeks of June, as currently forecast.

Research indicates that between 10 and 15 per cent of the population suffers from hayfever, rising to around 25 per cent in the 10- to 25-year-old age group. In the UK, around 95 per cent of hayfever sufferers are allergic to grass pollen. The number of those affected is known to be gradually increasing, as is the intensity of their symptoms.

Hayfever is caused by an allergic reaction to proteins contained in the pollen grains released by trees, grasses and weeds, plus mould spores. When they contact the eyes and nose lining of a sensitive individual, the classic hayfever symptoms of itchy watery eyes, blocked or stuffy nose and sneezing result.

Avoid direct contact

The simplest way to tackle the problem of hayfever is to avoid direct contact with airborne pollens or spores as much as possible. This means staying away from long grass and other obvious sources of pollen, keeping the windows shut in the home and car (or buying a car with a pollen filter) and wearing sunglasses.

However, even in the middle of towns it is impossible to avoid pollens altogether, so sufferers usually still need some kind of treatment.

Fortunately, there is an ever-increasing range of medicines available, both on prescription and in the chemists, which provide effective relief. These medicines come in a number of different forms: steroid injections; nasal sprays, eye drops and tablets. The choice will depend on the symptoms.

Antihistamine tablets are the most popular form of treatment, because they control the symptoms affecting both the eye and nose, and have rapid effects.

Sneezing

The pollen count is set to soar

They block the action of histamine, a substance produced by the body as a result of the allergic reaction. This relieves the symptoms of sneezing, itchy eyes and runny nose.

Although the original antihistamines made people drowsy, potentially impairing concentration whilst driving or operating machinery, the more recent ones do not have this drawback.

People who know that they suffer badly from grass pollen allergy should consult their doctor now. GPs will be able to advise on a suitable form of treatment before the main grass pollen season starts, such as one of the newest non-sedating antihistamines available on prescription only.