Silver has been used for at least six thousand years to prevent microbial infections. It has proven to be effective against almost all organisms tested, and it has played an important role in the development of radiology and improving wound healing, according to research out of the University of Cincinnati College of Medicine. Before the invention of the refrigerator, it was common practice to drop a silver coin into a container of milk as a preservative because silver was known to prevent the growth of algae, bacteria and other undesirable organisms.Dating back to ancient times, silver was also a popular remedy to stop the spread of diseases. Its use as a natural antibiotic continued all the way until the 1940s, when modern antibiotics arrived.        No refrigeration needed.