Climate change may extend allergy season: study

A woman tries to cover her mouth as she walks through cotton-like seeds from Poplar trees, also known as Cottonwood trees, on a Spring day in Beijing April 14, 2008.

WASHINGTON (Reuters) - Sneezing, congestion, and runny noses from hay fever may be lasting longer because climate change may be extending pollen seasons, doctors in Italy said on Monday.

Pollen seasons as well as the amount of pollen in the air progressively increased during a six-year study in Italy, the doctors told a meeting of the American Academy of Allergy, Asthma & Immunology in New Orleans.

The team at Genoa University recorded pollen counts, how long pollen seasons lasted and sensitivity to five types of pollen in the Bordighera region of Italy from 1981 to 2007.

"By studying a well-defined geographical region, we observed that the progressive increase of the average temperature has prolonged the duration of the pollen seasons of some plants and, consequently, the overall pollen load," Dr. Walter Canonica, who worked on the study, said in a statement.

The percentage of patients with reactions to the allergens increased throughout the study but it is not clear whether longer pollen seasons actually put more people at risk for developing allergies, the researchers said.

Allergic rhinitis, commonly known as hay fever, is a reaction to indoor or outdoor airborne allergens, such as pollen.

"Longer pollen seasons and high levels of pollen certainly can exacerbate symptoms for people with allergic rhinitis and for those who previously had minimal symptoms," said the AAAAI's Estelle Levetin, who was not involved in the study.

About 25 million Americans, nearly half of them children, had hay fever in the past year, according to the U.S. Centers for Disease Control and Prevention.

(Editing by Maggie Fox and Vicki Allen)