Canker sore

Canker sores, also called aphthous ulcers, are small, shallow lesions that develop on the soft tissues in your mouth or at the base of your gums. Unlike cold sores, canker sores don't occur on the surface of your lips and aren't contagious. They can be painful, however, and can make eating and talking difficult.

Most canker sores go away on their own in a week or two. Check with your doctor or dentist if you have unusually large or painful canker sores or canker sores that don't seem to heal.

Symptoms Causes Risk factors Prevention

Most canker sores are round or oval with a white or yellow center and a red border. They form inside your mouth — on or under your tongue, inside your cheeks or lips, at the base of your gums, or on your soft palate. You might notice a tingling or burning sensation a day or two before the sores actually appear.

There are several types of canker sores, including minor, major and herpetiform sores.

Minor canker sores

These most common canker sores:

  • Are usually small
  • Are oval shaped
  • Heal without scarring in one to two weeks

Major canker sores

These less common sores:

  • Are larger and deeper than minor canker sores
  • Have irregular edges
  • May take up to six weeks to heal and can leave extensive scarring

Herpetiform canker sores

These canker sores, which usually develop later in life:

  • Are pinpoint size
  • Often occur in clusters of 10 to 100 sores
  • Have irregular edges
  • Heal without scarring in one to two weeks

When to see a doctor

Consult your doctor if you experience:

  • Unusually large canker sores
  • Recurring sores, with new ones developing before old ones heal
  • Persistent sores, lasting three weeks or more
  • Sores that extend into the lips themselves (vermilion border)
  • Pain that you can't control with self-care measures
  • Extreme difficulty eating or drinking
  • High fever along with canker sores

See your dentist if you have sharp tooth surfaces or dental appliances that seem to trigger the sores.

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