Supplements containing colloidal silver aren't considered safe or effective for any of the health claims manufacturers make. Silver has no known purpose in the body. It's not an essential mineral.

Colloidal silver products are made of tiny silver particles suspended in a liquid — the same type of metal used in jewelry, dental fillings and silverware.

Manufacturers of colloidal silver supplements often promote their products by claiming that silver can boost the immune system, fight infection and treat cancer.

However, no sound scientific studies evaluating these health claims have been published in reputable medical journals. In the U.S., the Food and Drug Administration and the Federal Trade Commission have taken action against several companies for making unproven health claims.

When taken by mouth, silver builds up in your body. Over months to years, this can result in a blue-gray discoloration of your skin, eyes, internal organs, nails and gums. Doctors call this argyria (ahr-JIR-e-uh). It's usually permanent. In rare cases, high doses of colloidal silver can cause serious side effects, such as seizures and organ damage.

Colloidal silver may also interact with prescription medicines, including penicillamine (Cuprimine, Depen), quinolone antibiotics, tetracycline and levothyroxine (Unithroid, Levoxyl, Synthroid).