What are the symptoms of a canker sore?

Canker Sores: Generally, canker sores are painful and have a white crater in the center surrounded by a rim of bright red inflammation. They usually go away after a few days, but there are ways to treat them with topical cortisone or an injection or cortisone that will make them resolve much faster. See you dermatologist for help.

Canker sore: Canker sores are white ulcerations, or crater,with a red border usually on the floor of your mouth, or the area where your cheek meets the gum tissues. They last about a week and will heal naturally.

Canker sores: Here's a good resource to learn about canker sores (aphthous ulcers) http://www.mouthhealthy.org/en/az-topics/c/canker-sores