If you are coughing and sneezing already, prepare for it to get worse. Pollen levels are not due to peak until next month and, with the late spring, forecasters are predicting they could be higher than ever.
Cool spring temperatures have delayed the start of the growing season for the grasses that cause 95 per cent of hay fever in Britain. As the soil warms up, the resulting growing spurt could produce sudden high pollen counts.
The years ahead are likely to be even worse. Allergy to pollen is growing as a result of an increase in city living, exposure to traffic pollution and global warming. Pollen forecasts for the bank holiday weekend are low to moderate across the country, but are expected to rise sharply in the coming days.
Around 12 million people suffer from hay fever in Britain, caused by pollen grains irritating the nose, eyes and throat. The total has quadrupled in the last 50 years despite a fall in pollen counts due to the cutback in agricultural land. Experts blame air pollution from vehicle exhaust fumes, which accentuate the irritation caused by allergenic substances. Chemicals in the fumes are thought to sensitise the airways of susceptible individuals, making them more prone to allergies.
According to Professor Jean Emberlin, director of the National Pollen and Aerobiology Unit at the University of Worcester, the number of hay fever sufferers is expected to more than double over the next 20 years to 32 million. Changes in lifestyle including city living, increased stress, poorer diets, rising car ownership and global warming will all contribute to the rise, she says in a report commissioned by Kleenex.
"Increased sunlight and dry, hot summers will make photochemical smogs more frequent and intense, so there'll be more pollution and hay fever will be exacerbated," she said.
The worst plants for hay fever sufferers are the wind-pollinated trees and grasses, because they release vast quantitites of the microscopic grains which cause mayhem in respiratory tracts. Although only 25 per cent of sufferers are affected by birch pollen, it can trigger a much more severe reaction than the more common grass pollen.
The grass-pollen season usually starts in May, but it can vary by as much as a month depending on the weather and can continue until September. Pollen from almost any plant can cause an allergic reaction, but some are much worse than others. There are more than 1,200 species of grass, but only a few are known to cause allergic reactions.
At this year's Chelsea Flower Show, which ends today, a "pollen neutral" garden includes insect-pollinated plants like irises and peonies rather than trees and grasses which pump out industrial quantitites of pollen.