A canker sore is a painful, open sore in the mouth. Canker sores are white or yellow and surrounded by a bright red area. They are benign (not cancer). Canker sores can run in families. They may also be linked to problems with the body's immune (defense) system. The sores may occur after a mouth injury due to dental work, aggressive tooth cleaning, or biting the tongue or cheek.
Canker sores can be triggered by emotional stress, dietary deficiencies (especially iron, folic acid, or vitamin B-12), menstrual periods, hormonal changes, food allergies, and similar situations. They occur most commonly with viral infections. In some cases, the cause can not be identified. Treatment is usually not necessary. In most cases, the canker sores go away by themselves.
