Canker sores are internal in the mouth and herpes simplex is topical around the lips. My Grandmother always said canker sores were the result of an acid stomach. I remember getting them as a child but not as an adult. Oliva ----- Original Message ----- canker sores are inside the mouth on the cheek lining or gum; they are quite sore and feel round. (Yes I do have gluten intolerance). I have never found anything that helped. They go away in about a week.