CLIMATE change may be triggering a surge in cases of asthma and hay fever, according to a report by the world’s leading scientists.

Earlier springs, increased pollen production by plants and the spread of pollen-producing species could be causing allergic attacks in people who have never before suffered from hay fever.

The Intergovernmental Panel on Climate Change (IPCC) is warning that the problems for the allergic could increase as temperatures rise. Many experts believe that northern Europe — including Britain — is likely to be among the regions worst hit by the increase in allergies, partly because cold winters that previously kept pollen-producing plants at bay are becoming less common.

Some 5.2m people in Britain suffer from asthma and about 1,400 a year die from attacks. Many factors have been blamed for the condition, from smoking to lack of exercise, diet and the use of antibiotics.

For some 70% of asthma sufferers, wheezing attacks are triggered by allergy, of which Britain has some of the highest rates in Europe. An estimated 38.8% of teenagers in southeast England, the warmest part of the country, get hay fever, according to the national pollen research unit.

While many people are allergic to pets, house dust and mould, pollen is one of the most important triggers of asthma. Climate change is set to increase the amount of pollen in the air, with average world temperatures forecast to rise 2C3C by 2050.

The 2006 heatwave in Britain showed what may happen. “Last summer there were people who had never suffered hayfever before complaining of it because pollen levels were so high that their trigger point was reached,” said Professor Jean Emberlin, director of the national pollen and aerobiology research unit at Worcester University.

“Allergy is still increasing — there is a very clear link with more GP consultations and sales of over-the-counter allergy remedies. If climate continues to change the way it is, this is what will happen.”

The IPCC’s report is due to be published in July. “There is a theoretical probability that there will be an increase in allergic problems because of climate change,” said Bettina Menne, a scientist at the World Health Organisation in Rome and a leading author of the health section in the IPCC report.

It is expected to say that spring in northern Europe begins an average of 15 days earlier now than 30 years ago. This means that pollen-producing plants — such as grass, which triggers attacks in 90% of hayfever sufferers, and silver birch trees, which affect a quarter — have a much longer pollen-producing season than in the past.

Many scientists believe the spread of some plant species to Britain because of warmer weather could also increase allergic attacks. The new species include two plants which are present in only small numbers in Britain at the moment but which are spreading because warmer winters are failing to curb their growth.

Pellitory-of-the-wall (Parietaria judaica), a variety of nettle, is thought to affect some 80% of hayfever sufferers in Italy and is spreading from bases in Surrey and London. Ragweed (Ambrosia artemisiifolia), the main cause of hayfever in North America, is well established in Europe and has spread as far north as Holland and Scandinavia.

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