What causes aphthous stomatitis (canker sore)?

The cause of canker sores, small ulcers with a white or gray base and a red border that appear inside the mouth, is uncertain. They are not contagious, but can return frequently and may be only one canker sore or several. Some experts believe that immune system problems, bacteria or viruses may be involved.

Experts don’t know the exact cause of aphthous stomatitis, painful mouth ulcers also known as canker sores, but certain factors may make you more likely to develop them.  For example, stress, either emotional or physical, can lead to a canker sore episode. If other members in your family tend to get canker sores, you may be more likely to develop them too. Food hypersensitivity, a weak immune system, certain drugs, and some medical conditions (like inflammatory bowel disease) may also increase the risk for getting aphthous stomatitis.

If you're concerned about your canker sores, talk with your doctor; he or she may recommend over-the-counter ointments, suggest foods to avoid (hot, spicy or acidic foods), or even prescribe drugs to help the sores heal.

The actual cause of aphthous stomatitis is unknown. Medical researchers have discovered that these painful mouth sores seem to emerge in people with certain autoimmune diseases, such as AIDS, and intestinal conditions, such as celiac disease. The sores may also occur in people who have sensitivity to certain foods or oral cleansing products like mouthwash, toothpaste. Mouth sores can also form in people who have had a mouth injury or who are under a lot of stress.