You can also view previously answered questions in the HSW Question Archive .
Most people use it as an antiseptic.
It turns out it is not very good as an antiseptic, but it is not bad for washing cuts and scrapes and the foaming looks cool. The reason why it foams is because blood and cells contain an enzyme called catalase . 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.