Colloidal silver consists of tiny silver particles in a liquid that is sometimes promoted as a dietary supplement. Still, evidence supporting health-related claims is lacking. In fact, colloidal silver can be dangerous to your health. Colloidal silver can cause serious side effects, including argyria, a bluish-gray discoloration of the skin, which is usually permanent. Silver can build up in the body’s tissue, causing a bluish-gray discoloration of large areas of skin, especially those exposed to the sun. People have developed argyria from using homemade and commercial colloidal silver products. Colloidal silver also can cause poor absorption of some drugs, such as certain antibiotics and thyroxine (used to treat thyroid deficiency). There are no legally marketed prescription or over-the-counter drugs containing colloidal silver that are taken by mouth. The U.S. Food and Drug Administration warned in 1999 that colloidal silver is not safe or effective for treating any disease or condition.