To be honest not a lot of known about the stuff because nobody's incentivised to study it. There's a lot of people using it to treat a lot of things but I suspect that they don't know a lot about how it actually works.

It's said that it works through a mild oxidation reaction. Human cells are used to using oxygen & so are not effected. Anaerobic microbes & certain defunct cells are not resistant to high oxygen environments. Most of the organisms we consider good are aerobic.

What we know is that it's not like antibiotics that kill indiscriminately.