Germ Theory is a theory first coined by the French scientist Louis Pasteur. The theory states that diseases are caused by small life-forms that invade the body and have adverse effects on its growth, development or well-being.
Although his motivations are murky, it seems that the theory was concocted to benefit the dairy industry in order to reassure the public that their milk was actually a safe product to drink. Notice that even with the addition of hormones since the day of Pasteur, milk is still considered safe as long as the milk is "pasteurized."
The side effect of this theory is that people will avoid natural means of staying healthy, such as eating right and performing flushes of toxins, as long as they believe that their modern medicine is able to kill the tiny life-forms that have invaded their body.