Half the country may have hayfever

Professor Jean Emberlin, from the national pollen and aerobiology research unit at the University of Worcester, said the number of people with the condition would shoot up from the current level of around 24% of the population to about half.

Climate change is playing a role by altering the length of pollen seasons for trees and plants, she said.

For example, the birch pollen season, which affects around one in four people with hayfever, is now seen up to a month earlier than it was decades ago. The season for grass and weed pollen is also a few weeks longer than it used to be, she said.

Predicting future trends, she said: "Wetter winters will provide a soil moisture store for early growth of grass in the spring. This will tend to increase the amount of pollen produced on the plants. Drier weather in spring and summer will give more days with good conditions for pollen dispersal, leading to more high count days and severity of season."

Prof Emberlin, whose study was commissioned by Lloydspharmacy, said climate change would also increase the number of plants to which people are allergic. Increasing air pollution will also play a role, she added.

Prof Emberlin used a series of data to predict the future burden of hayfever. Her lowest estimate is that 36% of the population will suffer from hayfever and her highest is that 71% will. She thinks a median figure is that 54% will have hayfever by 2060.

Some experts have pointed to other factors behind the increase in allergies currently seen across the UK. These include the "hygiene hypothesis", which suggests we keep our homes and workplaces "too clean", use of antibiotics and changes in our diet.

Prof Emberlin said of her report: "These figures are a stark reminder of the effects climate change can have on our health. Hayfever not only has a tremendous impact on many aspects of life for the sufferer but also for the economy as a whole and it should be taken seriously."

She said the UK areas least susceptible to increases in pollen loads that cause allergies include coastal areas, especially in the West. The further north one goes, the shorter the growing season and the shorter the pollen seasons, causing less misery for hayfever sufferers, she said.