Canker sores, also called aphthous ulcers, are small, shallow lesions that develop on the soft tissues in your 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. They can be painful, however, and can make eating and talking difficult.

What does canker sore pain feel like?

Canker sores usually begin with a burning or tingling feeling. They may be swollen and painful. Having a canker sore can make it hard to talk or eat. Canker sores may hurt for 7 to 10 days.

What can be mistaken for a canker sore?

Leukoplakia. These lesions can also be mistaken for canker sores because they produce white spots or patches inside the mouth. Unlike a canker sore, leukoplakia patches aren't sensitive or painful. (4) This condition can be harmless like a canker sore, but some patches may become cancerous.