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Canker Sores

What Are Canker Sores?

Canker sores (also called aphthous ulcers) are small, shallow, painful, craterlike ulcers that appear on the moist tissues lining the inside of your mouth. They often occur two or three at a time, but it’s not unusual for 15 or more to appear at once. Unlike cold sores, canker sores are not contagious. They range from simple to complex, and occur predominantly in people between the ages of 10 and 40, especially women. Canker sores usually heal within two weeks, but they may recur. While they typically pose no serious health threat, severe canker sores can lead to malnutrition.  Even simple severe canker sores can make eating and talking an unpleasant experience.

Who Gets Canker Sores?

People of all ages can get canker sores.


  • You many have canker sores if you notice small, painful, white or gray, craterlike, red-rimmed ulcers located anywhere inside the mouth, including the gums, tongue, soft palate, inside the cheeks and inside the lips. Ulcers may appear individually singly or in groups.

Causes/Risk Factors

While the precise cause of canker sores is unknown, there are several things that may trigger them:

  • Injuries due to rough dentures, toothbrushes, chipped or jagged teeth, dental work, or burns from hot food or liquids may lead to mouth ulcers.
  • Canker sores are more likely to appear during periods of emotional stress or physical exhaustion.
  • Bacterial infections may induce canker sores.
  • Irritation from certain foods, including citrus fruits, pineapple, vinegar, or highly salted foods, may cause mouth ulcers.
  • Food allergies, allergic rhinitis, and certain vitamin and mineral deficiencies may be associated with canker sores.
  • Often canker sores occur spontaneously.

What If You Do Nothing?

Painful and irritating as they are, canker sores usually go away in 7 to 15 days, with or without treatment.


  • In severe or persistent cases, a biopsy of the ulcers may be taken to rule out oral ulcers occurring in association with other disorders including cancer and erosive lichen planus (a chronic skin and mucous membrane disease of unknown cause).
  • A blood sample may also be required.


  • A prescription medication, amlexanox (Aphthasol), is approved specifically for treating canker sores. It comes in paste form and, when applied as directed, has been shown to ease pain and accelerate healing by a day or two. You can also take the following steps toe ease discomfort:
  • Apply an ice cube to the sore area to relieve pain.
  • Rinse the mouth several times a day with warm salt water.
  • Avoid spicy or acidic foods that irritate the ulcers.
  • For painful sores, ask your pharmacist to recommend an over-the-counter anesthetic drug or protective gel to reduce pain and inflammation.
  • For recurrent or more severe ulcers, a doctor may recommend using an antiseptic mouthwash. In addition, a doctor may also prescribe topical anesthetics or corticosteroids to reduce symptoms and inflammation, and to speed healing.


  • Brush and floss your teeth regularly.
  • Any mouth injury can get infected, so if you unconsciously bite the inside of your cheek, try to break the habit.
  • Try to determine if certain foods seem to trigger canker sores and then avoid those foods.

When To Call Your Doctor

  • Call your doctor if, in addition to canker sores, you develop a high fever or swollen glands.
  • Consult your doctor if you experience severe pain from the ulcers, if they substantially increase in number, or if you develop canker sores more than three times a year.
  • Call your doctor if the ulcers persist for longer than two weeks despite treatment.

Reviewed by Michael Kapner, DDS, General and Aesthetic Dentistry, Norwalk Medical Center, Norwalk, CT. Review provided by VeriMed Healthcare Network.