Hydrogen peroxide works as a disinfectant by oxidizing compounds common to organic life. It is particularly reactive in the presence of an enzyme known as catalase, which occurs naturally in cells and triggers the release of water and oxygen. This release causes hydrogen peroxide's characteristic fizzing, according to HowStuffWorks.
Hydrogen peroxide molecules consist of two hydrogen atoms in a so-called "peroxide" bond with two atoms of oxygen, according to Lenntech. Hydrogen peroxide dissolves proteins by cracking apart and releasing water, H2O and free radicals of oxygen, which have the potential to disinfect and oxidize water, open wounds and other potentially biotic environments. Concentrated hydrogen peroxide is highly corrosive, though the rate at which it corrodes surrounding materials can be controlled to an extent by managing pH levels and the presence of chemicals such as iron.
Pure hydrogen peroxide is almost never used for medical or industrial purposes; a concentrated solution is flammable and potentially toxic, and dilute concentrations of between 3 percent and 35 percent are adequate for most applications. The breaking of the peroxide bond is strongly exothermic, and the heat released during oxidation is also potentially dangerous, especially as the reaction gives off pure oxygen as a waste gas, notes Lenntech.