Colloidal silver is a water solution containing nanometer-sized silver particles in suspension. Total silver content is expressed in milligrams of silver per liter of water, or mg/L, which is numerically equal to parts per million (ppm). Silver has been used for at least six thousand years to prevent microbial infections.

It proved to be effective against nearly all organisms tested and played an important role in the development of radiology and in improving wound healing, according to research from the University of Cincinnati College of Medicine.