Since a cut or scrape contains both blood and damaged cells, there is lots of catalase floating around. Catalase does this extremely efficiently - up to 200,000 reactions per second. The bubbles you see in the foam are pure oxygen bubbles being created by the catalase. Try putting a little hydrogen peroxide on a cut potato and it will do the same thing for the same reason - catalase in the damaged potato cells reacts with the hydrogen peroxide. Hydrogen Peroxide does not foam in the bottle or on your skin because there is no catalase to help the reaction to occur.
Hydrogen perxoide is stable at room temperature.
For more information on how enzymes work, see the HSW article entitled How Cells Work . Inc. All rights reserved. Please Click Here for a complete list of previously answered questions. If you would like to ask a question you can click here .