Lots of people look forward to the warmer weather that spring and summer should bring, but it's also hay fever season.

I have suffered from hay fever since I was a young boy and, along with about 12 million other people in the UK, have to put up with runny noses, sneezing, and itchy eyes from June to the end of July.

Summer's coming, but so are the sneezes

There are different types of pollen which can affect us, although 90% of those with hay fever suffer because of grass pollen.

Simply, pollen from various trees, plants and grasses gets blown around in the wind, we inhale it, and this stimulates cells in our noses which produce histamines.

It is these histamines which produce the symptoms associated with hay fever.

Tree pollen appears earlier in the season, with birch, hazel, horse chestnut and alder being the main culprits - approximately 25% of sufferers are allergic to birch pollen.

The importance of accurate pollen forecasts has grown as the number of sufferers has dramatically increased.

Virtually unknown at the beginning of the 19th century, the number of reported cases grows every year.

City menace

While part of this increase is down to greater awareness, there are other contributory factors.

Some studies have shown that incidences of hay fever are greater in cities than in the surrounding countryside.

Summer fun can be curtailed by hay fever

In fact, it seems likely that vehicle pollutants such as particulates, nitrogen dioxide and sulphur dioxide either make victims more susceptible to allergens, or themselves produce irritation in the airways.

Diet and lifestyle are also believed to play their part in making some more vulnerable than others - non-smokers are less likely to be sufferers.

Dehumidifiers and ionisers and other filtration systems may reduce the amount of pollen within the home.

While sprays and drops may deal with localised symptoms, antihistamines offer the best control for multiple symptoms for most.

But to be fully effective, medication may be acquired before the onset of the hay fever season and dosages may need to be modified depending on the daily pollen count.

Pollen index

The pollen count is an average of a number of pollen readings throughout the day.

This data, based on readings from 33 monitoring sites around the country, is collated by the National Pollen Research Unit.

The index may be low (1-3), moderate (4-5), high (6-7) or very high (8-10) according to the number of grains of pollen per cubic metre.

Two-day forecasts use current pollen levels, forecast winds, cloud, rain and temperatures to predict the likely levels.

As well as appearing on BBC Wales weather forecasts, the latest reports also appear on Ceefax, page 426.

See Derek Brockway on Wales Today at 1330GMT and 1830GMT weekdays on BBC One Wales and hear him on BBC Radio Wales.

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