The Hygiene Hypothesis: How Getting Dirty Could Prevent Allergies

Those who grow up in rural areas, such as on farms, are less likely to be afflicted by immune system ailments like asthma and allergies than people who live in urban areas. Some researchers hypothesize that exposure to germs as a child helps the body's immune system become stronger, while living in a clean and sterile environment leaves the immune system weaker. Some scientists now believe that they know how this "hygiene hypothesis" works, says NPR.

They have found that microbes that grow in the gut keep the immune system in control. Without the microbes, the immune cells in the lungs and intestines become overactive, increasing the risk of developing asthma.

Co-author of the study, Dr. Richard Blumberg, is the chief of gastroenterology at Boston's Brigham and Woman's Hospital. He explained the discovery: "We made the serendipitous observation that these cells were dramatically enriched in the lung and colon in mice that lacked any microbes." The microbes were lacking in mice who had been raised in a germ-free laboratory environment. The immune response occurring inside these mice looked very similar to what happens in people who have asthma and other immune system conditions.

The findings of this study support other research that has shown that exposure to microbes in childhood lowers the risk of immune-based problems like food allergies and asthma.