I have worked for a holistic dentist for over 10 years now and work with folks that are incredibly chemically sensitive. A ton of folks have issues with peppermint, glycerin, carrageenan, fluoride and really all the other junk in most "natural" toothpastes.
My doc recommends the following, doesn't really taste great, but gets the job done without issues!!
If this link doesn't take you to "tooth powder, you can search easily on their...