Colloidal silver isn't considered safe or effective for any of the health claims manufacturers make. Silver has no known purpose in the body. Nor is it an essential mineral, as some sellers of silver products claim.
Colloidal silver products are made of tiny silver particles suspended in a liquid — the same type of precious metal used in jewelry, dental fillings, silverware and other consumer goods.
Colloidal silver products are usually marketed as dietary supplements that are taken by mouth. Colloidal silver products also come in forms to be injected or applied to the skin.
Manufacturers of colloidal silver products often claim that they are cure–alls, boosting your immune system, fighting bacteria and viruses, and treating cancer, HIV/AIDS, shingles, herpes, eye ailments and prostatitis.
However, no sound scientific studies to evaluate these health claims have been published in reputable medical journals. In fact, the Food and Drug Administration has taken action against some manufacturers of colloidal silver products for making unproven health claims.
It's not clear how much colloidal silver may be harmful, but it can build up in your body's tissues over months or years. Most commonly, this results in argyria (ahr–JIR–e–uh), a blue-gray discoloration of your skin, eyes, internal organs, nails and gums. While argyria doesn't pose a serious health problem, it can be a cosmetic concern because it doesn't go away when you stop taking silver products.
Rarely, excessive doses of colloidal silver can cause possibly irreversible serious health problems, including kidney damage and neurological problems such as seizures. Colloidal silver products may also interact with medications, including penicillamine (Cuprimine, Depen), quinolone antibiotics, tetracycline and thyroxine (Levothroid, Levoxyl, Synthroid) medications.
http://www.mayoclinic.org/healthy-living...er/faq-20058061 
