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    Too-Clean Homes May Encourage Child Allergies

    Exposure to a little dust, dander in infancy might prime tots' immune systems, research finds


    As many as half of all 3-year-olds in the United States suffer from wheezing illnesses, and recurrent wheezing and allergies are considered a risk factor for asthma in later life, researchers said. According to the American Lung Association, asthma remains one of the most common pediatric illnesses, affecting about 7 million American children.

    The new study involved 467 inner-city newborns from Baltimore, Boston, New York City and St. Louis. Doctors enrolled the babies in the study while they were still in the womb, and have been tracking their health since birth, Wood said.

    Investigators visited the infants' homes to measure the levels and types of allergens. They also collected dust in about a quarter of the homes and analyzed its bacterial content.

    They found that infants who grew up in homes with mouse and cat dander and cockroach droppings in the first year of life had lower rates of wheezing at age 3, compared with children not exposed to the allergens.

    Wheezing was three times as common among children who grew up without exposure to such allergens, affecting 51 percent of children in "clean" homes compared with 17 percent of children who spent their first year of life in houses where all three allergens were present.

    Household bacteria also played a role, and infants in homes with a greater variety of bacteria were less likely to develop allergies and wheezing by age 3.

    Children free of wheezing and allergies at age 3 had grown up with the highest levels of household allergens and were the most likely to live in houses with the richest array of bacterial species, researchers found.

    "The combination of both -- having the allergen exposure and the bacterial exposure -- appeared to be the most protective," Wood said.

    Both Wood and Mahr cautioned that these findings need to be verified, and that parents shouldn't make any household decisions based on them.

    For example, parents shouldn't adopt a dog or cat assuming that its presence will help immunize their kids against allergies and asthma, Wood said. At the same time, they shouldn't ditch their family pet, either.

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