as everyone else has said, peroxide = bad... personal experience here - i did use h2o2 (3% from drugstore) on my initial 20/18g gunned ear-piercings... this was a very bad idea (even tho it was the 'recommended' treatment from the lady who gunned me)..
the h2o2 solution actually did do some foaming in my piercing - and what that meant (besides being kinda fun/cool) was that it was 'eating away' all the blood and damaged-skin from the piercing see this link. what ended up happening in my ear (that was foaming) was that i developed a little 'fold' of 'eaten-away' skin from the 'cleansing' action of the h2o2. thus, my ears were actually damaged from the h2o2 - do not do this !!!
also, while h2o2 is indeed a 'green' substance to use - you might want to look at comment-9 under this link for a quote regarding wound-care with it... basically, do NOT put anything on (or irrigate/clean) a wound (yes, a stretch/piercing is a skin-wound) that you would not feel comfortable/safe to put in/on your eye !!! this is a handy rule-of-thumb if you ask me... and also helps explain why saline solution (sss) is the recommended treatment around these here parts...
edit - corrected first link a bit, and
to answer amanda - i assume the answer is yes (stuff in bottle given at gun piercings), but i was gunned at a portable earring-stall inside the mall-main-area and the gal just 'told' me to go get the peroxide from the drugstore... (thus, i actively did this to myself... sigh) to be fair, the fact that only my left-ear has this odd skin-collapse/fold is prolly due to the little internal-white-bump (which i think was a zit or somesuch) that only existed on my left-earlobe... basically - there was some sort of 'internal-to-that-ear' yet 'close-enough-to-the-piercing' skin-condition/item that the broken-skin from the gun-piercing allowed the peroxide to 'reach inside' and 'eat away' creating the fold/collapse near the actual piercing-hole... my RIGHT ear, never seemed to 'foam' when cleaning the piercing and it never developed this minor skin-fold... i really should try and take a pic of it to explain a bit better...
exactly 8.25250000001mm (0g) ear lobes ? goal reached, but currently downsizing/healing old wounds... so that i can create -new- ones... lol...
HII method: harold is insane... make sure to read everything i say and follow the most-insane ideas. if youre lucky - you can be insane too. 8-)
standard disclaimer here