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Medical Author:

Siamak T. Nabili, MD, MPH

Siamak T. Nabili, MD, MPH

Dr. Nabili received his undergraduate degree from the University of California, San Diego (UCSD), majoring in chemistry and biochemistry. He then completed his graduate degree at the University of California, Los Angeles (UCLA). His graduate training included a specialized fellowship in public health where his research focused on environmental health and health-care delivery and management.

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Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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In this Article

• Canker sores facts
• What are canker sores?
• What are symptoms of canker sores?
• What are the causes of canker sores?
• Are canker sores the same as fever blisters?
• What steps can be taken to help canker sores?
• What is the treatment for canker sores?
• What kind of topical medications (gels or ointments) are available for canker sores?
• Can mouthwash solutions be used with canker sores?
• What oral medications are available to help canker sores?
• What should I do if I get canker sores frequently?
• What research is being done in the area of canker sores?
• Patient Comments: Canker Sores - Effective Treatments
• Patient Comments: Canker Sores - Experience
• Patient Comments: Canker Sores - Symptoms
• Patient Comments: Canker Sores - Topical Medications
• Find a local Ear, Nose, & Throat Doctor in your town
• Canker Sores Index

Canker sores are usually found on the movable parts of the mouth, such as the tongue or the inside lining of the lips and cheeks, and at the base of the gums. The ulcers begin as small oval or round reddish swellings that usually burst within a day. The ruptured sores are covered by a thin white or yellow membrane and edged by a red halo. Generally, the sores heal within two weeks without scarring. Fever is rare, and the sores are rarely associated with other diseases. Usually, a person has only one or a few canker sores at a time.

Most people experience their first bout with canker sores between the ages of 10 and 20. Children as young as 2 years old, however, can develop the condition. The frequency of canker sore recurrences varies considerably. Some people have only one or two episodes a year, while others may have a continuous series 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 generalized disorder of the digestive tract. Vitamin C deficiency has also been associated with canker sores.

Emotional stress and local trauma or injury to the mouth, such as sharp metal braces, brushing with hard toothbrushes, and hot foods can lead to canker sores. Smoking and dentures can also contribute to the problem. Some studies have shown a connection with toothpaste containing sodium lauryl sulfate in some individuals, although, other studies have not found any connection.

Other possible causes of canker sores include illnesses in which the immune system causes swelling or inflammation of the body tissues (autoimmune disorders). Examples of autoimmune disorders are systemic lupus erythematosus, Crohn's disease, and Behçet's disease.

Female sex hormones also apparently play a role in causing canker sores. Many women experience bouts of the sores only during certain phases of their menstrual cycles. Additionally, most women experience improvement or remission of their canker sores during pregnancy. Researchers have used hormone therapy successfully in clinical studies to treat some women.