Researchers at UC Berkeley's Center for Children's Environmental Health Research, studying 514 children born in 1999 and 2000 in California's Salinas Valley, found that children born in high mould season (fall and winter) were three times more likely to develop wheezing by the age of two than children born at other times of the year. The researchers also found that total pollen concentration exposure during the first three months of life increased the risk of early wheezing. This is the first study to look at the potential role of early life exposure to multiple outdoor fungal and pollen groups in the development of asthma.

As many as 40% of children who wheeze early in life may go on to develop childhood asthma, especially if they have other allergic symptoms. ‘We are not in a position to say conclusively why some children develop asthma, or to even suggest precautionary measures to help babies born in the fall and winter,’ the study’s senior author, Dr Ira Tager, said. ‘We already know that family history is a major risk factor for developing asthma, but the role environmental factors play is still being fleshed out. What this study does is provide valuable clues about airborne allergens that are worth exploring further.’

The research appears in the February online edition of Thorax.

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First Published in April 2009

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