Barnyard Dust Offers a Clue to Stopping Asthma in Children

Scientists say they may have found a sort of magic ingredient to prevent asthma in children: microbes from farm animals, carried into the home in dust.

The results of their research, published on Wednesday in The New England Journal of Medicine, were so convincing that they raised the possibility of developing a spray to do the same thing for children who do not have regular contact with cows and horses.

It is a pressing problem because as many as 10.6 percent of grade-school children have asthma, according to data from the Centers for Disease Control and Prevention. And there is no cure for this chronic and frightening disease.

The discovery originated with an idea that has been around for years: that a growing number of children were developing asthma because their daily environments were simply too clean...