my daughter 8 had a ugly mouth ulcer, looks like a cold sore but between her gum and cheek, was a slit it her mouth and white. I had her use 3% peroxide full strength 2 times a day, in the meantime her toothache stopped and the ugly mouth ulcer is gone. I'm looking to buy the food grade h202 to keep in the freezer, after diluting some in a other container too. H202 has soo many benefits.
When I tried swishing the peroxide around in my mouth with a bit of water it took down some of the swelling in a wound on the inside of my cheek. It also helped the pain I had with my teeth and gums.