Asthma risk is lower for children living on farms, according to two studies.
Children living on farms are surrounded by a greater variety of germs, which, in theory, helps them build a stronger immune system. The study findings support what is known as the hygiene theory, which states that contact with bacteria and other microbes is necessary to building a normal immune system.
According to Markus Ege, an epidemiologist at the Children's Hospital of Munich and first author on the paper that covered both studies, the key appears to be exposure to a diversity of bugs, not just more of them.
"Bacteria can be beneficial for asthma," said Dr. Ege. "You have to have microbes that educate the immune system. But you have to have the right ones."
The study helps provides evidence that the reduction in risk is indeed significantly related to the variety of bacteria and other bugs a child is exposed to. However, since the biggest effect appeared to be related to prolonged exposure to cows and pigs, Dr. Ege said it would not help for parents to take their children to a farm two or three times a year or to get a dog or other pet for the purpose of exposing their children to microbes.
