How should I treat canker sores?

Ask the doctor Q. I suffer from recurrent canker sores. What is the best way to treat and prevent these mouth ulcers? A. Canker sores, also known as aphthous ulcers, are small ulcers that appear on the inside of your cheeks and lips and sometimes on or under your tongue. They should not be confused with cold sores (fever blisters), which are due to a herpes simplex virus. …