Does Exposure to Allergens During Infancy Influence Childhood Asthma?


Infants who are exposed to pet or pest allergens may be less likely to develop asthma during childhood, according to a new study published in the Journal of Allergy and Clinical Immunology.

Infants who are exposed to pet or pest allergens may be less likely to develop asthma during childhood, according to a new study published in theJournal of Allergy and Clinical Immunology.1

The findings, which are supported by the National Institutes of Health, reveal that exposing infants to high indoor levels of certain allergens may have a preventive effect on the development of asthma by 7 years of age.

The study, called the URECA study, followed children in urban areas from birth through 7 years of age. Beginning in 2005, the researchers enrolled 560 newborn infants from Baltimore, Boston, New York, and St. Louis, who were at high risk of developing asthma. At the end of the study, the researchers had sufficient data to assess 442 of the enrolled children by the age of 7 years old.

Out of the 442 children, 29% had developed asthma. The researchers found that higher levels of cockroach, mouse, and cat allergens in dust samples collected from the children’s homes during the first 3 years of life were associated with a lower risk of asthma by age 7. Although dog allergens also exhibited a similar association, it was not statistically significant.

The researchers also confirmed that factors such as prenatal exposure to tobacco smoke and maternal stress and depression contributed to a higher risk of developing asthma. During the study, the researchers noted that presence of cotinine, which results from the breakdown of nicotine in the body, found in the umbilical cord blood of newborns increased asthma risk. Additionally, reported maternal stress and depression during the child’s first 3 years of life were also found to be associated with higher asthma risk.

“Our observations imply that exposure to a broad variety of indoor allergens, bacteria, and bacterial products early in life may reduce risk of developing asthma,” James E. Gern, MD, the prinicipal investigator of URECA and a professor at the University of Wisconsin-Madison, said in a press release about the study.2“Additional research may help us identify specific targets for asthma prevention strategies.”

However, the study is ongoing, and the researchers explained that they hope to identify additional information about influencing early-life factors by dividing the children into groups based on characteristic of their allergies and asthma.


1. O’Connor GT, Lynch SV, Bloomberg GR, et al. Early-life home environment and risk of asthma among inner-city children.J All Clin Immunol. 2017. DOI:

2. Exposure to pet and pest allergens during infancy linked to reduced asthma risk [news release]. NIH’s website. Accessed September 19, 2017.

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