Jonathan Hatch posted a careful description of his efforts, successful and unsuccessful, to get rid of tongue canker sores. Among his recommendations was to use a toothpaste without SLS, and he specified Rembrandt. Please note that Rembrandt contains peroxide -- often helpful,though not always. BUT it also does contain SLS (sodium lauryl sulfate), the fifth from last of its listed ingredients. Medical research has supported his claim that SLS encourages tongue cankers. Listerine 1-minute mouth swishes worked for me: half a capful of Listerine rolled around in my mouth for 1 minute, then spit out. The very first treatment was alleviating; after five within twenty-four hours, I was almost completely cured