Dr. McBride based his assertion on several lines of evidence. In addition to the timing of the asthma epidemic, he said, there is now a plausible explanation for how acetaminophen might provoke or worsen asthma, a chronic inflammatory condition of the lungs. Even a single dose of acetaminophen can reduce the body's levels of glutathione, an enzyme that helps repair oxidative damage that can drive inflammation in the airways, researchers have found.
"Almost every study that's looked for it has found a dose-response relationship between acetaminophen use and asthma," Dr. McBride said. "The association is incredibly consistent across age, geography and culture."
A statistical link between acetaminophen and asthma has turned up in studies of infants, children and adults. Studies have also found an increased risk of asthma in children whose mothers who took acetaminophen during pregnancy.
Image: Asthma inhaler, via Shutterstock.