Canker sore

Updated: 2017-06-13

Overview

A canker sore is a small, shallow sore inside the mouth or at the base of the gums. Unlike a cold sore, it doesn't occur on the lips and isn't contagious.

Symptoms

It can be painful and make it hard to eat and talk.

Treatments

Most canker sores clear on their own in 1 to 2 weeks. Treatments, if needed, include mouth rinses, pastes, and medication.