Colloidal silver, a suspension of the element silver in a solution, usually water, has a long history of use as an antimicrobial agent. While colloidal silver doesn’t have any known immune-enhancing effects, it may help to promote wound healing. Recent studies have indicated the antibacterial activity of colloidal silver.
As far as toxicity, colloidal silver can cause permanent skin, eye, and organ discoloration when ingested or used on the skin in high doses or over long periods of time. Although not dangerous to physical health, this discoloration may cause psychological and social harm. As a result of this potential harm, the FDA has issued a warning to consumers regarding the use of supplements containing silver. In addition, some people have allergic reactions to silver-based wound dressings, fabrics, and medical appliances.
Source: Current Problems in Dermatology