Canker sores are defined as a small white/yellow sore, surrounded by redness, located inside the mouth. They are not contagious, but they sure are painful!!! Sodium Lauryl Sulfate (SLS) is a common chemical ingredient found in toothpaste. It is an inexpensive detergent that causes our toothpaste to foam, but for some people with a sensitivity to this chemical, it causes tissue trauma, which is a leading cause of canker sores. So check the label on your toothpaste; if it includes SLS and you get these painful sores frequently, you may want to change your toothpaste.
– from Pam B. (Dental Hygienist)