Barnyard Microbes and Childhood Asthma

It is easy to imagine why children who are raised on farms might grow up healthy: there is plenty of fresh air, exercise, and exposure to sunlight. In fact, studies from Europe, North America, and Australasia provide convincing evidence that allergic diseases and asthma are less likely to develop in children who live on farms than in those who do not.¹ Surprisingly, according to the findings of Ege and colleagues in this issue of the Journal, ² the mechanism responsible for these health effects appears not to be related to clean living but instead to bacteria and fungi from the barnyard. . . .