Metallic silver, like copper, is an antibacterial agent, which was known to the ancients and first scientifically investigated and named “oligodynamic”. The oligodynamic effect (from Greek oligos "few", and dynamis "force") is a biocidal effect of metals, that occurs even in low concentrations. The effect was discovered by Karl Wilhelm von Nägeli in 1893, although he did not identify the cause. Brass doorknobs and silverware both exhibit this effect to an extent. 

Silver is safe.  Both the scientific community and government regulators from around the world agree that silver is safe and useful.  Humans will not experience adverse effects if exposed to silver in moderation, but silver compounds can cause some areas of the skin and other body tissues to turn gray or blue-gray. Doctors call this condition "argyria." 

According to the US Agency for Toxic Substances:  “Argyria occurs in people who eat or breathe in silver compounds over a long period (several months to many years). A single exposure to a silver compound may also cause silver to be deposited in the skin and in other parts of the body; however, this is not known to be harmful. It is likely that many exposures to silver are necessary to develop argyria. Once you have argyria, it is permanent. However, the condition is thought to be only a "cosmetic" problem. Most doctors and scientists believe that the discoloration of the skin seen in argyria is the most serious health effect of silver.”

The metabolism of bacteria is adversely affected by silver ions at concentrations of 0.01–0.1 mg/L. Therefore, even less soluble silver compounds, such as silver chloride, also act as bactericides or germicides. In the presence of atmospheric oxygen, metallic silver also has a bactericidal effect due to the formation of silver oxide, which is soluble enough to allow it to show antibacterial properties. Concentrations of bacteria are reduced rapidly by adding colloidal silver, which is particularly effective due to its high surface area. Even objects with a solid silver surface (e.g., table silver, silver coins, or silver foil) have a bactericidal effect. Silver drinking vessels were carried by military commanders on expeditions for protection against disease. It was once common to place silver foil or even silver coins on wounds for the same reason.

Silver sulfadiazine is used as an antiseptic ointment for extensive burns. An equilibrium dispersion of colloidal silver with dissolved silver ions can be used to purify drinking water at sea. Silver is incorporated into medical implants and devices such as catheters. Surfacine (silver iodide) is a relatively new antimicrobial for application to surfaces. Silver-impregnated wound dressings have proven especially useful against antibiotic-resistant bacteria. Silver nitrate is used as a haemostatic, antiseptic and astringent. Silver ions are increasingly incorporated into many hard surfaces, such as plastics and steel, as a way to control microbial growth on items such as toilet seats, stethoscopes, and even refrigerator doors. Among the newer products being sold are plastic food containers infused with silver substances, which are intended to keep food fresher, and silver-infused athletic shirts and socks, which minimize odours.

Although silver has powerful antimicrobial and biocidal properties that destroy harmful bacteria such as Legionella, E. Coli and S. aureus, its toxicity to human cells is low by comparison. It’s no wonder silver has found its way into so many applications in our homes, hospitals, and workplaces today. 

Here are just a few of silver’s many health benefits:

Silver substances are extremely effective, even in tiny amounts.

Just a small quantity of silver can outdo the antimicrobial abilities of harsh, artificial compounds—and significantly lower the risk of adverse side effects from chemical exposure.

Bacteria and fungi are powerless to resist silver.

Silver and most silver compounds are toxic for bacteria and fungi. The antibacterial action of silver is dependent on the silver ion. Silver, used as a topical antiseptic, is incorporated by bacteria it kills. Thus dead bacteria may be the source of silver which may kill additional bacteria. 

Silver help in the fight against antibiotic-resistant “superbugs.”

Antibiotic-resistant bacteria strains can be highly dangerous, especially to those most vulnerable to infections. Silver can neutralize both antibiotic-resistant bacteria and regular bacteria, because it’s extremely difficult for the pathogens to develop a resistance to silver.  Some research shows adding a metal to a traditional antibiotic that doesn't work anymore makes the drug effective again.

Ionised silver has proven to effectively control pathogens in water systems due to its superior residual effect and potential to remove biofilms

Because ionised silver is in synergy with ionised copper effective against pathogens independent of water temperatures, it is also no longer necessary to run hot water temperatures at very high temperatures, therefore, saving energy and reducing carbon footprint. More information on this topic can be found in this report entitled ‘Controlling Legionella pneumophila in water systems at reduced hot water temperatures with copper and silver ionization’, published in the American Journal of Infection Control.