Mouth sores

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Hand-foot-and-mouth disease

Mouth sores

Aphthous stomatitis

Most mouth sores are cold sores (also called fever blisters), canker sores, or other irritation caused by:

• A sharp or broken tooth or poorly fitting dentures
• Biting your cheek, tongue, or lip
• Burning your mouth from hot food or drinks
• Braces
• Chewing tobacco

Cold sores are caused by the herpes simplex virus and are very contagious. Usually, you will have tenderness, tingling, or burning before the actual sore appears. Cold sores usually begin as blisters and then crust over.

The herpes virus can live in your body for years. It only appears as a mouth sore when something triggers it, such as:

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• Another illness, especially if there is a fever
• Hormone changes (such as menstruation)
• Stress
• Sun exposure

Canker sores are NOT contagious. They can appear as a single pale or yellow ulcer with a red outer ring, or as a cluster of these sores. The cause of canker sores is not clear, but may be related to:

• A virus
• A temporary weakness in your immune system (for example, from the cold or flu)
• Hormone changes
• Irritation
• Stress
• Low levels of vitamin B12 or folate

For unknown reasons, women seem to get canker sores more often than men. This may be related to hormone changes.

Less commonly, mouth sores can be a sign of an illness, tumor, or reaction to a medication. Such illnesses can be grouped into several broad categories:

• Autoimmune disorders (including systemic lupus erythematosus )
• Bleeding disorders
• Cancer
• Infection (such as hand-foot-mouth disease)
• Weakened immune system -- for example, if you have AIDS or are taking medication after a transplant

Drugs that may cause mouth sores include:

• Aspirin
• Barbiturates (used for insomnia)
• Chemotherapy drugs for cancer
• Gold (used for rheumatoid arthritis)
• Penicillin
• Phenytoin (used for seizures)
• Streptomycin
• Sulfonamides

Review Date: 11/14/2010
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).