Silver

WARNING: Do not use silver supplements (unless you want to form the next blue man group ;) ). 

Silver is pretty common, in that it is found in jewelry, silverware (what a surprise!), coins, mirrors, conductors, old photography film, etc. But despite silver's ubiquity, it can be detrimental to the human body if ingested in large quantities.

Argyria is an ailment that causes skin to turn blue or blue-grey after ingestion of silver containing compounds. This condition was more common during the early 20th century before it was discovered that medicine containing silver could have detrimental effects, but argyria has hit the news again with the increase in holistic remedies containing silver and apocalypse scares (people drink silver in fear that the post-apocalyptic world will be lacking antibiotics). Check out the following video:

The blue color from argyria is a result of sun exposure, so to cut down on the cosmetic look of the condition, persons with argyria could potentially become recluses ala Howard Hughes and would turn to a normal color. But because argyria has no known side effects other than turning colors, it is not deadly, so most people with the condition tend to continue their silver drinking habits. Strange, right?


Fun Fact: During the 19th century, silver was commonly used as a disinfectant. In this manner, sailors would place a silver coin in wine and water barrels to keep the drinks potable. American pioneers did the same by placing silver coins in milk to keep it from spoiling.