It is known that once a child has developed asthma, exposure to certain allergens may worsen their symptoms. Exposure to pollen, pet dander, or dust mites should be avoided for children with the condition.
However, new research suggests that pet allergens, together with some pest ones, may have the opposite - and therefore a preventative - effect, as long as the children are exposed to the allergens before the age of 3.
The study was led by Dr. James E. Gern, a professor at the University of Wisconsin-Madison, and it was conducted as part of the ongoing Urban Environment and Childhood Asthma (URECA) study.
Studying allergens and asthma
The URECA study started in 2005. Since then, researchers have examined asthma risk factors among 560 children born in Baltimore, MD, Boston, MA, New York City, NY, and St. Louis, MO.
These children were at high risk of developing the condition because at least one of their parents had asthma or other allergies.
As part of the URECA study, children born in 2005 were clinically followed until now, and the present study assessed these children until they reached the age of 7.
Of the 560 inner-city children, Dr. Gern and team had a sufficient amount of data on 442. Of these, 130 children (or 29 percent) developed asthma.
Allergens were sampled from the children's homes at three different time points: when the children were 3 months old, 2 years old, and 3 years old.
The researchers used 16S ribosomal RNA sequencing to analyze the house dust microbiome. They identified 202 bacterial taxa that were more abundant in the homes of children with asthma, and 171 that were less abundant.
Cockroach, mouse, and cat allergens
The study found a strong inverse correlation between high concentrations of cockroach, mouse, and cat allergens present in the house dust and the risk of asthma.
The higher the concentrations of these allergens before the age of 3, the lower the risk of asthma before the age of 7.
Further analysis revealed that these together with dog allergens correlated with a lower risk of asthma. However, dog allergen on its own did not yield a statistically significant correlation with asthma risk.
According to Dr. Anthony S. Fauci, who is director of the National Institute of Allergy and Infectious Diseases, "We are learning more and more about how the early-life environment can influence the development of certain health conditions."
"If we can develop strategies to prevent asthma before it develops," Dr. Fauci adds, "we will help alleviate the burden this disease places on millions of people, as well as on their families and communities."
"Our observations imply that exposure to a broad variety of indoor allergens, bacteria, and bacterial products early in life may reduce the risk of developing asthma [...] Additional research may help us identify specific targets for asthma prevention strategies."
Dr. James E. Gern