For years, I have been plagued by canker sores in my mouth. Sometimes I get two or three at once. Sometimes, right after they heal, I get another one growing right after. It causes a lot of pain, and eating is a nightmare because of it.
I used to think it had something to do with stress or lack of sleep. But recently, I came across this thread on Reddit. Basically, it says that toothpaste that contains sodium laureth sulfate (or sodium lauryl sulfate, or sodium dodecyl sulfate) will possibly make it easier for cuts to form in your mouth, and that ingredient will irritate it and make it worse. I looked at the Colgate toothpaste I was using, and it did indeed contain sodium lauryl sulfate. What does sodium lauryl sulfate do anyway? It's a foaming agent (also in shampoos, etc) that makes it seem like whatever you're using is doing its job. So, it's useless.