There was (is?) a homeopathic movement involving the consumption of colloidal silver. Proponents suggest that colloidal silver provides any number of health benefits, including a significant boost to the immune system which leaves them malady free (except for the fact that the consumption of excessive amounts of silver results in the irreversible condition known as Argyria, in which the victim's skin turns blue).
This is not to be confused with Methemoglobinemia, a genetic condition which interferes with the amount of oxygen that is delivered to the skin, causing it to turn blue. A famous series of cases occurred when two Kentucky clans carrying the recessive Methemoglobinemia gene intermarried and began producing blue offspring. They were known as The Blue Fugates of Kentucky: