This is false. Some people claim that hydrogen peroxide, taken by mouth or injected into a vein, can treat cancer. There is no evidence that this approach works, and it is dangerous. Hydrogen peroxide is more commonly used as bleach, and several people have died because they have put peroxide into their body. Health food stores sometimes sell “food-grade” hydrogen peroxide at concentrations that are 10 times greater than the levels approved for use on the skin. If you dissolve this chemical in water and drink it, you could vomit, burn your digestive tract, and even die.