Canker sores (or apthous ulcers) are typically small, ulcer-like lesions that develop on the soft tissues inside the mouth or at the base of your gums. Unlike cold sores, canker sores don't occur on the surface of your lips and they aren't contagious.

Canker sores are typically round, flat, and white in color with a red border. These sores can be painful, however, which can make eating or speaking uncomfortable. A softer, blander diet is recommended to reduce irritation as well as maintaining proper hydration with plenty of fluids (preferably water).

Typically these sores typically resolve on their own within 7-10 days. Call for further evaluation if the lesions do not clear up on their own within 2 weeks, are large in size, occur frequently, associated with a fever, or you have difficulty with maintaining proper hydration and diet. Sometimes apthous ulcers can be a symptoms of underlying medical conditions and so blood work and a medical evaluation are recommended as well.