By Leigh Parry
Exposure to high levels of fungal spores and pollen after birth may increase a child’s risk of developing asthma, researchers reported today.
It is one of a few studies looking at the correlation between birth months and increased levels of airborne allergens.
Researchers, led by Dr Kim Harley from the University of California at Berkeley, USA, studied the respiratory health of 514 children for two years.
They found children born between mid February to March 2000 and between late August 2000 to January 2001 were three times more likely to wheeze before the age of two than children born outside those months.
These dates coincided with the periods of highest circulating levels of outdoor fungal spores – specifically basidospores and ascospores, according to the report in the journal Thorax.
The researchers assessed levels of specific types of T cells (Th1 and Th2) measured in blood samples.
T cells are involved in the inflammatory processes that can trigger wheezing or asthma.
Children exposed to high levels of pollen from cypress, pine and alder during their first three months were also significantly more likely to wheeze. They also had lower Th1 levels and higher Th2 levels by the age of two.
The authors said it was thought that the priming of a child’s T cells to respond to allergens happens in the late stages of pregnancy and that early exposure to allergens after birth may reinforce an abnormal T cell response.
Thorax, Online First 2009; doi 10.1136/thx.2007.090241
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