What are the causes of canker sores?
The cause of canker sores is not well understood. More than one cause is likely, even for individual patients. Canker sores do not appear to be caused by viruses or bacteria, although an allergy to a type of bacterium commonly found in the mouth may trigger them in some people. The sores may be an allergic reaction to certain foods. In addition, there is research suggesting that canker sores may be caused by a faulty immune system that uses the body’s defenses against disease to attack and destroy the normal cells of the mouth or tongue. British studies show that in about 20 percent of patients, canker sores are due partly to nutritional deficiencies, especially lack of vitamin B12, folic acid, and iron. Similar studies performed in the United States, however, have not confirmed this finding. In a small percentage of patients, canker sores occur along with gastrointestinal problems, such as an inability to digest certain cereals. In these patients, canker sores appear to be part of a g
