The rise in temperatures associated with climate change might have an unexpected consequence: more allergies among more people.
New research from Italy suggests that higher temperatures are lengthening the pollen season for some plants and trees, increasing the pollen load they produce and causing a rise in the number of people who are developing allergies to certain pollens.
"The increase of global radiation determines an advance [of pollen season] and an increased period of exposure to the pollens," said study author Dr Renato Ariano, director of the allergy service at Bordighera Hospital in Italy. Ariano said the increased exposure to pollen can cause more people who are susceptible to allergy to actually develop pollen allergies.
Ariano presented the findings in New Orleans at the annual meeting of the American Academy of Allergy, Asthma & Immunology.
Pollen season starts earlier
For nearly 30 years, Ariano and his colleagues have been recording pollen counts, the length of pollen seasons and the prevalence of people sensitised to five major pollens in the Bordighera region of Italy - birch, cypress, olive, grass and parietaria, a common plant in that region.
The Bordighera region is in western Liguria, on the Mediterranean Sea at the border of Italy and France, said study author Dr Giovanni Passalacqua, an assistant professor of allergy and respiratory diseases at Genoa University in Italy. Bordighera "has a very mild Mediterranean climate and is surrounded by a rural landscape where flowers and olives are cultivated," he said.
Between 1981 and 2007, the researchers noted an earlier start for pollen season. In the case of parietaria, the pollen season began about 80 days sooner at the end of the study period than it did at the beginning. For olive trees, the pollen season began about 30 days sooner, Passalacqua said.
More people affected
At the same time, the researchers also tested area residents, using skin prick testing to assess the levels of sensitisation to the five pollens. If someone reacts on a skin prick test, they're said to be sensitised to that substance. However, being sensitised to a substance in an allergy test doesn't always translate to noticeable symptoms, though there's often a correlation between the two.
"We observed a constant increase of the percentage of subjects sensitised to olive, parietaria and cypress, whereas the percentage of subjects sensitised to dust mites remained unchanged over 27 years," Passalacqua said.
Estelle Levetin, a professor of biology who chairs the biological sciences faculty at the University of Tulsa in Oklahoma, US, said that "the data already show that pollen seasons could be longer and pollen levels could be higher, and although this needs more study, it may be that the pollen grain is becoming more allergenic when plants are grown with higher carbon dioxide levels."
This means that people with allergies might need to start taking allergy medications earlier and continue them for a longer period of time, Levetin said. Anyone who feels that their allergies are starting earlier should discuss this with their doctor, she said. - (Serena Gordon/HealthDay News, March 2010)