Early Exposure to Allergens Can Reduce the Risk of Asthma

Caroline Petrow-Cohen

Around 25 million Americans have asthma, and that number is only growing. Asthma is also the leading chronic disease in children, causing difficulty breathing, wheezing, and tightness in the chest, among other symptoms. It is previously known that the severity of asthma is affected by the environment a child grows up in. Recently, researchers have explored the effects of allergen exposure on infants in order to “identify early-life environmental risk factors for childhood asthma” and potentially find exposures to prevent it. The results they found are significant, concluding that “higher house dust concentrations of cockroach, mouse, and cat allergens in the first 3 years of life were associated with lower risk of asthma.”

Study Design

Pregnant women from inner-city Baltimore, Boston, New York City, and St. Louis were recruited for the study. They or the father of their child must have had a history of asthma, allergies, or eczema.

After birth, scientists carefully monitored the health and environment of the newborn babies. Questionnaires were distributed regularly regarding the mother and child’s health and lifestyle. Levels of IgE, the antibody that causes allergic reactions in response to an allergen, for milk, egg, peanut, German cockroach, dust mites, dog, and cat were measured periodically. Skin prick tests were administered for further allergen testing as well. Researches also collected samples of dust from the houses of the participants, analyzing levels of allergenic proteins of cockroach, dog, cat, and dust mite.

Once the children reached 7 years of age, they were classified as having asthma or not. A classification of asthma was determined if a child was diagnosed with asthma by a doctor, had used asthma medication(s) for 6 months, and/or reported 2 or more wheezing episodes within the past year.


Of those children determined to have asthma by age 7, researchers observed that many had mothers with asthma, or experienced wheezing at age 3.

For those children who didn’t have asthma, “higher allergen concentrations in house dust summed over those of the specimens collected at 3 months, 2 years, and 3 years of age” were observed in many households. In particular, exposure to cockroach, cat, and mouse seemed to lower the risk of asthma by age 7 significantly. 

The results of this study show great promise in preventing asthma in future generations, as families can now take effective, preventative measures against asthma. Though counterintuitive, exposing infants to more allergens, rather than none at all, can actually significantly increase the chance of an asthma-free life.

Darlene Fung ’19



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