One of the most painful, frequently occurring conditions that plague patients is canker sores on the cheeks, lips, tongue, gums, or palate. They can even occur outside of, but close to, the mouth. Fortunately, whether you treat them or not, canker sores usually disappear in about one to two weeks. The cause of these objectionable sores is unknown, but fatigue, some foods, irritation with a sharp object or toothbrush, emotional distress, or other reasons are potential causes. What can you do about canker sores?