Microbes are essential parts of every form of life, and 99 percent of them have specific duties for keeping our bodies going, like helping us digest our food, synthesizing vitamins, and regulating our immune systems. Only a tiny portion of the bacteria inside of us are harmful, yet it seems like humans―particularly those in developed countries― are bent on getting rid of every bug we can. The repercussions of this anti-bug behavior are getting serious: As reported in USA Today, although scientists can't yet prove direct cause-and-effect, researchers have linked changes in our microbial inhabitants with rising rates of obesity, allergies, autoimmune diseases and other chronic illnesses.