I started using Rembrant for cankers (C) years ago after I bought a tube as a last resort while on a trip to New York. I have found that it is the only thing that really works to prevent and to heal cankers in the mouth. I told my Orthodontist about it and he recommends it to his patients with braces and it really does work. It is getting harder and harder to find in stores so, when I did find it at Amazon, I bought several tubes of it.