Vinegar and Peroxide (mouth sores) I learned from my mother to treat mouth sores (whether a bit lip/tongue or a cold sore) with a mixture of hydrogen peroxide and vinegar (any type of vinegar seems to work okay, but Apple Cider is the best and most palatable). I have always used this remedy, and nothing else has ever worked. I've tried many OTC remedies and none relieve the pain AND speed the healing process like this mixture. What I want to know is... why doesn't H2O2 alone have as good an effect? Some people seem to swear by it, but it has never been as effective when I tried it alone.