Precious metals can be used to treat a variety of diseases. Gold in particular can be converted in a compound, such as gold sodium thiomalate, and used to reduce pain and inflammation from rheumatoid arthritis. However, gold compounds are rarely prescribed – and not just because of gold’s price and rarity.
When gold is introduced to the body parentally (e.g. via injection, infusion, etc.) over a long enough period of time, a skin condition known as chrysiasis develops. Chrysiasis is permanent, but causes no other effects to the body besides changing the color of the skin. When gold compounds are repeatedly administered, gold particles build up in the deep layers of skin. This build up, in addition to sun exposure, causes the skin to become blue-grey or grey-purple.
Argyria is an extremely similar condition that occurs when too much silver builds up in the body. The difference between the two conditions is that argyria produces a color closer to slate-grey or blue grey. Argyria can also onset from oral administration of silver, whereas chrysiasis cannot (which could explain why gold food seems to be much more popular than silver food).