Canker Sores (Cold Sores) Overview

Canker sores, also called aphthous ulcers, are small superficial lesions that develop on the soft tissues of the mouth and the base of your gums. Unlike cold sores, canker sores do not occur on the surface of your lips and is not contagious. They can be very painful, however, and can make eating and speaking difficult.

Most canker sores go away by themselves within a week or two. Consult your doctor or dentist if you have mouth ulcers or unusually large or painful ulcers that do not seem to heal.