Colloidal silver
Colloidal silver is a liquid suspension of microscopic particles of silver. A colloid is technically defined as particles which remain suspended without forming an ionic, or dissolved solution. The broader commercial definition of "colloidal silver" includes products that contain various concentrations of ionic silver, silver colloids, ionic silver compounds or silver proteins in purified water. Colloidal silver with concentrations of 30 parts per million (ppm) or less are typically manufactured using an electrolysis process, whereas colloidal silver with higher concentrations of 50 ppm or more are usually either silver compounds such as silver chloride and silver iodide or are solutions that have been bound with a protein to disperse the particles.

# History and Applications
Concentrations of colloidal silver at 5 parts per million or higher have been found to kill numerous infectious bacteria. Prior to 1938, colloidal silver was widely used by physicians as a mainstream antibiotic. It was produced by pharmaceutical companies under various names, including Protargol and Argyrol. But the material was costly and the pharmaceutical industry developed fast-acting, less-expensive sulfa drugs and penicillin. Colloidal silver has been approved by the EPA as a disinfectant for hospitals and medical centers.
Compounds of silver also have a long history in medicine. Silver nitrate solutions were introduced by Crede in 1880 to protect newborn infants' eyes from infection, but have largely been replaced by antibiotic ointments since 1978. (Silver nitrate solutions are not the same thing as a suspension of colloidal silver.) Silver-containing cremes such as silver sulfadiazine have been used in burn centers for more than 100 years.

# Method of Action
Colloidal silver is reported to kill bacteria via the oligodynamic effect by inhibiting the expression of enzymes and other proteins essential to ATP production.

# Toxicities

## Argyria
Long-term intake of silver products may result in a condition known as argyria, one symptom of which is a blue or gray discoloration of the skin.  It occurs when sunlight interacts with silver deposited in the skin, in the same way that silver particles in photographic film darken when exposed to sunlight.  It can occur both via ingestion of silver, or through topical application of silver to the skin. While generally considered permanent, some have claimed to have reversed it. Death of a 71 year old man has been reported following four months use of oral colloidal silver.
Many scientific articles report cases of argyria after ingestion of colloidal silver.

## Government reactions
In August 1999 The U.S. Food and Drug Administration (FDA) issued a ruling banning colloidal silver sellers from claiming any therapeutic value for the product. Unless a drug has undergone the rigorous safety and efficacy testing required of pharmaceuticals no medical benefits can be claimed. Such testing has not been conducted with colloidal silver, so the product now has the status of a dietary supplement in the US (dietary supplements cannot claim to cure diseases, only that they "support healthy functioning"). The FDA has issued warnings to Internet sites selling or promoting colloidal silver as an antibiotic or for other medical purposes. If no medical benefits are claimed, colloidal silver is sold as a supplement, and as long as the products comply with all other FDA regulations, its sale is considered legal. In 2002, the Australian Therapeutic Goods Administration ruled that colloidal silver-containing products were no longer exempted from therapeutic goods legislation and had to meet the requirements of other products covered by this law. A TGA investigation found that "there are no current legitimate uses of colloidal silver and that the Surveillance Section of the TGA be requested to investigate the illegal availability of colloidal silver products because of concerns about their significant toxicity. The reasons for the recommendation were that:
"There is little evidence to support therapeutic claims made for colloidal silver products; 
the risk to consumers of silver toxicity outweighs the value of trying an unsubstantiated treatment, and bacterial resistance to silver can occur; and 
efforts should be made to curb the illegal availability of colloidal silver products, which is a significant public health issue."