Early Exposure to Dust, Household Dust Lowers Asthma Risk in Children

Babies exposed to household dirt, pollen and pet dander have lower risk of developing allergies, wheezing or asthma, researchers said.

The study shows that exposure to common allergens might be beneficial in boosting immunity of babies. Previous research has shown that children growing up on farms have lower asthma risk.

Related studies have also shown that babies in crowded city areas have increased risk of asthma and allergies due to constant exposure to roach allergens and small, airborne particles. The new study, from Johns Hopkins Children's Center, shows that babies exposed to allergens before their first birthday have lower risk of developing breathing problems or allergies. But, the same protective effect wasn't seen in children who encountered dust and grime one year after birth.

"Our study shows that the timing of initial exposure may be critical," said Robert Wood, M.D., chief of the Division of Allergy and Immunology at the Johns Hopkins Children's Center, one of the study authors, according to a news release. "What this tells us is that not only are many of our immune responses shaped in the first year of life, but also that certain bacteria and allergens play an important role in stimulating and training the immune system to behave a certain way."

Understanding how new born babies react to household dust and dander could help doctors develop strategies to reduce asthma and wheezing occurrence in children. In the U.S., about 25 million people suffer from asthma, of which at least 7 million are children.

The study was based on data from 467 inner-city newborns from Baltimore, Boston, New York and St. Louis. Researchers followed the children for three years. The team measured levels of allergens in subjects' homes and looked for signs of allergies via periodic blood tests.

Researchers found that children exposed to mouse droppings had lower risk of wheezing than children who weren't exposed to dirt. Also, babies exposed to different kinds of pollutants were less likely to develop allergies and asthma later in life than other children.

Nearly 8 percent children with allergy and wheezing had been exposed to pollutants during first few months of life compared with 41 percent children who didn't develop the condition. In all, children who had encountered allergens were three times more likely to develop wheezing.

Related studies have shown that having a dog at home reduces children's risk of developing eczema later in life.

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