Hay fever epidemic

Sales of hay fever medicines in London have soared in recent weeks because of an earlier than expected outbreak of runny noses, itchy eyes and persistent sneezing.

The premature arrival of the dreaded hay fever season has been blamed by experts on a combination of unusual weather patterns. Pollen counts have been high because of unseasonally warm weather and plenty of sunshine.

"In the past three weeks sales of hay fever treatments have more than doubled because of high levels of birch tree pollen," said Maeve O'Connell, pharmacist at Boots' Liverpool Street station branch.

But what is it about life in the capital that appears to increase the risks of hay fever - a condition many might associate with grassy meadows or fields of bright yellow oil seed rape?

Experts say the combination of high levels of birch pollen, the main trigger at this time of year, and inner-city air pollution can be intolerable for some hay fever sufferers.

Tests show that in parts of the country levels of birch pollen - which affects an estimated 25 per cent of the UK's 13 million hay fever sufferers - are nearly five times up on last year at around 900 grains per cubic metre of air.

"This year, birch pollen levels have been higher and peaked this month," says Professor Jean Emberlin from the National Pollen Research Unit in Worcester. She believes the way pollen interacts with common air pollutants can make the hay fever season especially miserable for Londoners.

"There's a lot of evidence that indicates pollen growing in a polluted atmosphere produces more proteins, which act as allergens. The proteins on the pollen are changed by the influence of pollution."

Prof Emberlin, who has worked in London and studied the effects of air pollution on hay fever sufferers, says harmful gases and deposits in the atmosphere mingle with pollen grains. The pollen reacts as if it is being invaded by a disease and immediately starts to increase productionof certain types of proteins as a means of defence.

"If you imagine a pollen grain travelling through the air in London, its surface is sticky and it will pick up lots of polluted particles, including car exhausts and diesel fumes. These particles then mop up the proteins from the surface of the pollen grain."

But high levels of birch pollen do not automatically mean a summer of misery for all hay fever sufferers, insists Prof Emberlin. The main catalyst is grass pollen - affecting up to 75 per cent of all hay fever victims - which does not normally become a problem until late May at the earliest. A change in the weather between now and then, with cooler temperatures, stronger winds and some rain, could dampen things down.