Bacteria are a necessary part of a healthy immune system. They help build our body's defenses and fight future illnesses.

Following mice study scientists concluded that the mice who had been exposed to microbes had stronger immune systems than the germ-free mice. It was noticed that the germ-free mice had exaggerated inflammation in their lungs and colon, similar to what is seen in humans who have asthma and ulcerative colitis.
The study is published in the journal Science.
Source-Medindia