“Provides extra oxygen atoms that not only slow down the spread of cancer but also kill tumor cells.” That’s the claim on a Web site discussing the internal use--through either drinking or injecting--of “35% Food Grade hydrogen peroxide,” more than 10 times as strong as the hydrogen peroxide sold for disinfecting cuts. The chemical is being promoted as a treatment for cancer, AIDS, and other serious conditions. An article on one site suggests it can be used as an alternative to antibiotics.

But using hydrogen peroxide this way can be dangerous or even deadly, the U.S. Food and Drug Administration warned in July 2006. While the manufacturers’ directions call for diluting their products before use, there’s no established safe threshold for drinking or injecting hydrogen peroxide. Taken orally, the chemical might cause gastrointestinal irritation or ulcers, the agency said. Injecting it might cause inflammation, emboli (bubbles in blood vessels), and potentially life-threatening allergic reactions. And the 35 percent concentration can burn the skin or even combust.

The FDA sent warning letters in July to two Web sites marketing high-strength hydrogen peroxide for health purposes, saying the products were misbranded and sales made under those claims were illegal. As of press time, the sites were still operating but one had changed some statements.

The idea behind ingesting hydrogen peroxide stems from a now-discredited theory that cancer and AIDS thrive on a lack of oxygen in the body. Hydrogen peroxide (which has one more oxygen atom than water) supposedly provides extra oxygen that helps the body fight disease. But there’s no reliable evidence that such “oxygenation therapy” has any medical value.

CR’s take. Use only the 3 percent solution, and only for cleaning wounds. If you use it to rinse a sore in your mouth, avoid swallowing.