Many people understand that H2O2 kills bacteria but they are stumped on how H2O2 can kill the 'bad' bacteria and not the 'good' bacteria.

H2O2 oxidizes bad (anaerobic) bacteria because the bacteria that is bad for you depends on fermentation to thrive and survive. This bacteria is opportunistic, meaning that it also uses any sugary/starchy/processed food that you eat as its main diet.

This is usually the problem when Candida has been diagnosed in a person.

The good (aerobic) bacteria is not killed by H2O2 because it depends on oxygen to thrive and survive, just as your body does.

OxygenLynne
http://www.oxygentherapyprogram.com/h2o2info.html