What Are Canker Sores?

What are canker sores?

Canker sores are a kind of ulcer in the mouth caused by:

  • injuries to the inside of the mouth, like when you bite the inside of your cheek or braces scrape your lip
  • things like stress, menstrual periods, and food allergies
  • an immune system reaction

Canker sores, which tend to run in families, usually pop up alone but sometimes show up in small clusters, causing pain or burning that starts to go away within several days.

Unlike cold sores, canker sores are not contagious, but they can cause pain or burning.

Canker sores go away on their own, but in the meantime, your doctor may recommend a special mouth rinse or ointment to help relieve pain. You also may want to avoid foods and drinks that can irritate the open sore, such as acidic orange juice and tomatoes, and scratchy toast and pretzels.

If you have a lot of pain, the canker sores don't improve within 2 weeks, or if you get canker sores frequently, talk to your doctor.

Reviewed by: Mary L. Gavin, MD
Date reviewed: January 2012

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Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.

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