Usually it’s the tartar control ingredients that are irritating. Sometimes it’s the flavoring. Sodium Laurel Sulfate(SLS), a foaming agent, has been shown to cause canker sores in some people.
The Chinese have been substituting diethylene glycol instead of the glycerine, which is more expensive. Glycerine is frequently used as a sweetener and a thickening agent.
Thank you both for your input. I don’t want Floride in my toothpaste, either, but I do have some Peelu, which is made in the U.S.A. I will use that and see if it heals my problem.