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Canker Sores

Facts about canker sores

  • Canker sores, also known as aphthous ulcers, are among the most common causes of painful sores in the mouth.
  • The classic canker sore lesion is a small (less than 1 centimeter) oval to round ulcer with a red (erythematous) border.
  • Canker sores can occur on the gums, under the tongue, inside the cheeks and inside the lips (mucous membranes).
  • Less than half of the U.S. population have canker sores at some point in their lives, but many people with them will have multiple episodes.
  • The exact cause of canker sores is not known; however, the following factors have been suggested to precipitate outbreaks.
  • Unless canker sores are a recurrent problem, no exams, tests, or treatment is needed.
  • The peak incidence of canker sores occurs among people in adolescence and young adulthood. They become less frequent as we age.
  • Canker sores occur more frequently in whites, nonsmokers, and people with higher socioeconomic status.
  • Inflammatory bowel diseases (Crohn's disease and ulcerative colitis) have been associated with canker sores.
  • Canker sores are not contagious.
  • Home remedies for canker sores include salt water mouth rinses, vitamin B12, aloe Vera, and several herbs.
  • OTC ointments, liquids, and other medicine helps canker sores heal and soothes pain.
  • Canker sores are not the same thing as cold sores. Cold sores or "fever blisters" occur on the outer lip, whereas canker sores are found inside the mouth.

What does a canker sore look like (pictures)?

Canker sores are painful ulcers involving the mouth. The person shown here also has Behçet's syndrome, which among other things causes canker sores.
Canker sores are painful ulcers involving the mouth. The person shown here also has Behçet's syndrome, which among other things causes canker sores. (Photo courtesy F. Fehl III, MD)
Last Reviewed 11/20/2017

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Patient Comments & Reviews

The eMedicineHealth doctors ask about Canker Sores:

Canker Sores - Symptoms

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Canker Sores - Medical Treatment

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Canker Sores - Causes

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Canker Sores - Home Remedies

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canker sores picture in children

Canker Sores vs. Cold Sores (Fever Blisters)

Canker sores are not the same as cold sores (fever blisters). Some of the differences between canker sores and cold sores are:

  • Cold sores break out on the lips. Canker sores break out inside the mouth.
  • Canker sores are not caused by the herpes virus.
  • Canker sores are not contagious.
  • A cold sore starts as a blister and then ruptures.

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