Sentry, I would modify your answer slightly. Exogenous peroxide is ineffective, but endogenous peroxide is a very effective endogenous antiseptic. It might surprise some to learn that human neutrophils (a type of white blood cell) produce both hydrogen peroxide and hypochloric acid (bleach) from the combined activities of the enzymes phagocyte oxidase, superoxide dismutase and myeloperoxidase. As it turns out, there are rare human diseases where some of these proteins are mutated or absent, and in those states, people are highly susceptible to certain infections. The best characterized example is a deficiency in the ability to produce superoxide via phagocyte oxidase in a disorder known as chronic granulomatous disease http://www.nlm.nih.gov/medlineplus/ency/article/001239.htm. Thus, I would say that our own immune system effectively uses peroxide and bleach to kill bacteria and fungi.