The medical uses of silver include its incorporation into wound dressings to treat external infections, and its use as an antiseptic and disinfectant in medical appliances. Silver is also promoted within alternative medicine in the form of colloidal silver, although this particular application has not yet been proved to be either effective or safe.
The silver ion (Ag+) is bioactive and in sufficient concentration readily kills bacteria in vitro. Silver also kills bacteria in external wounds in living tissue, so physicians use wound dressings containing silver sulfadiazine (Ag-SD) or silver nanomaterials to treat external infections.     Wound dressings containing silver are increasing in importance due to the recent increase of antibiotic-resistant bacteria, such as MRSA. The disinfectant properties of silver are used in medical applications, such as urinary catheters and endotracheal breathing tubes, where the silver content is effective in reducing incidences of catheter-related urinary tract infections and ventilator-associated pneumonia (VAP), respectively.    Silver is also used in bone prostheses, reconstructive orthopaedic surgery and cardiac devices as well as on surfaces and fabrics to reduce the spread of infection. 
Since the 1990s, “colloidal silver”, a liquid suspension of microscopic silver particles, has been marketed as an alternative medicine, often claiming impressive “cure-all” qualities. The effectiveness of these products has never been scientifically proven, and in some jurisdictions, it is currently illegal to include such claims in product advertisements. Medical authorities and publications advise against the ingestion of colloidal silver preparations, because of their lack of proven effectiveness and because of the risk of adverse side effects, such as argyria.   Historically, colloidal silver was also used as an internal medication to treat a variety of diseases. Their use ntinued in the 1940s, due to the development of safe and effective modern antibiotics and concern about adverse side effects.