THE QUESTION: Though they are powerful disease-fighters, antibiotics have downsides, too. Overuse can lead to bacterial resistance, and, in children, antibiotics sometimes cause diarrhea or allergic reactions. When given to very young children, might these drugs also play a role in the development of asthma?

THIS STUDY analyzed data on 62,576 children, 7 years and younger, including 26,693 who had been prescribed at least one course of antibiotics before their first birthday. By age 3, about 18 percent of the children had developed wheezing or asthma. Compared with those who had never taken antibiotics, children who had taken the medication in infancy were twice as likely to have developed wheezing and 60 percent more likely to have asthma that persisted at least until age 7. As the number of antibiotics the children took grew, so did their odds of having asthma; it doubled for those who had taken five courses of the drugs. Use of antibiotics early in life seemed to have no effect on the development of asthma after age 3.

WHO MAY BE AFFECTED? Children, who are often prescribed antibiotics to treat respiratory and ear infections. Antibiotics combat bacterial infections, either by killing the bacteria or keeping them from reproducing. Asthma, a lung condition that makes breathing difficult, can be triggered by allergens such as mold, dust and pollen or by such nonallergic factors as anxiety, cold air or exercise. An estimated 9 million American children have asthma.

CAVEATS The study noted an association between early antibiotic use and the presence of asthma, but it did not prove that the medication caused the disease. Data used in the study did not include such risk factors for asthma as whether the children had a family history of asthma or whether their parents smoked.

FIND THIS STUDY May issue of Annals of Allergy, Asthma & Immunology.

LEARN MORE ABOUT childhood asthma at (click “for Parents”). Learn about antibiotics at

The research described in Quick Study comes from credible, peer-reviewed journals. Nonetheless, conclusive evidence about a treatment's effectiveness is rarely found in a single study. Anyone considering changing or beginning treatment of any kind should consult with a physician.