Throughout history silver has been used as a preservative and to fight infections. Colloidal silver is a suspension of the element silver in a solution, usually water. Silver, like mercury, was used as a medicine starting in the late 1800s. Its primary application was as a topical antiseptic. Use of silver, in the form of silver nitrate solution, is still required by law in most states to be used in newborns as a topical eye drop to prevent eye infections.