H2O2 or hydrogen peroxide is a very interresting compound, (as a kid a had an accident, i drank a sip out of a soda bottle, wich was full of 30% h2o2. the scarriest thing of my child hood. well maybe not the scariest). also higher percentage solutions such as 95-100% are used as rocket fuel or even explosives, which are very unstable. so, 6% concentration of this is used even for cleaning wounds (as well as similar oxidizing agents). i think it would rather burn the bacteria in your mouth, than the flesh of your tongue that would happen with the 30%. i presume it is safe to use hydrogen peroxide for cleaning.
p.s. sorry for my bad english.