First Year May Be Critical for Lowering Asthma and Allergy Risk
Childhood exposure to allergens and germs is generally believed to protect against the development of asthma and allergy, but a new study suggests that this effect happens only with exposure in the first year of life.
Researchers studied 560 children at high risk for asthma in Baltimore, Boston, New York and St. Louis, giving them yearly clinical examinations and regularly testing their homes for bacteria and cat, dog, cockroach, mouse and dust mite allergens. The study, several of whose authors have received funds from pharmaceutical companies, appears in The Journal of Allergy and Clinical Immunology .
By age 3, 44 percent of the children were sensitized to at least one allergen, and 36 percent had recurrent wheezing . Over all, the more exposure children had to cockroach, mouse and cat allergens, the higher their risk for wheezing.
But timing was important. Only 17 percent of those exposed to all three allergens during the first year of life had recurrent wheezing, compared with 51 percent of those exposed to none of them. Children who were free of allergies and wheezing tended to have the highest first-year exposure to both allergens and bacteria.
The practical implications of the finding are still not clear. “We think this information will eventually be important to develop some preventative strategies,” said an author, Dr. Robert A. Wood, a professor of pediatrics at Johns Hopkins, “but there are no strategies that are applicable to an individual household.”