I just read about this in my Microbiology textbook

Here's a link I found quickly enough...even though it refers to Veterinary practice...

http://answers.yahoo.com/question/index?qid=20080211065619AAkhVX1

Hydrogen peroxide damages healthy tissue surrounding the infection, which doesn't mean that it shouldn't be used, just that it does indeed slow down the healing process - to what degree probably depends on the severity, type, location, surface area, depth etc., of the infected tissue. I've also read that it actually promotes the formation of free radicals which can also damage healthy tissue.