Canker sore! Help?

Ke
I suffer from canker sores and I've done everything to prevent them I changed my toothpaste to non sodium lauryl sulfate. Idk if I'm allergic to anything. But I have one right now cuz my period is going to start I don't usually get them as a sign my period is about to start. But does anyone know how to prevent them? Or make it go away fast? Salt water doesn't work for me.
Thanks