Are there benefits to taking colloidal silver or to buying a "colloidal silver generator"? —R.L.B., Bryn Mawr, Calif.

No, and the supplement can be dangerous. Colloidal silver consists of tiny silver particles suspended in liquid. It’s often touted as a treatment for allergies, arthritis, cancer, diabetes, and even infections such as anthrax and swine flu. The generators supposedly perform the alchemy necessary to brew your own silver supplement. But there are no known benefits to ingesting silver. Although it does have some mild germ-killing powers, it’s too weak to be used as an antibiotic. More important, it can be toxic. Possible effects include birth defects, permanent bluish discoloration of the skin, nails, gums, and whites of the eyes, and in severe cases, organ damage and neurologic disorders. And the supplements may interfere with certain drugs.