Exposure to house dust early in life reduces infant's asthma risk later in life

A new study has revealed that infants exposed to a diverse range of bacterial species in house dust during the first year of life appear to be less likely to develop asthma in early childhood.

Children who were neither allergic nor prone to wheezing as three-year-olds were the most likely to have been exposed to high levels of bacteria, and paradoxically, to high levels of common allergens.

In fact, some of the protective bacteria are abundant in cockroaches and mice, the source of these common allergens, according to UC San Francisco researcher Susan Lynch, PhD, a lead author for the multi-institutional study.

Lynch also found that exposure during the first year of life to household dust containing higher levels of two specific groups of bacteria that are abundant in the human gut-Bacteriodes and Firmicutes-was associated with less asthma risk in the analysis of data from 104 inner-city babies in four cities.

Lynch, an associate professor of medicine with the Division of Gastroenterology at UCSF, said there is no obvious mechanism explaining the association, but the evidence supports earlier research that strongly pointed to the influence of microbial species in shaping immune responses.

The study is published online in the Journal of Allergy and Clinical Immunology.