What Are Canker Sores?

Canker sores (also called aphthous ulcers) are small, painful, crater-like ulcers in the lining of the mouth. They often occur two or three at a time, but it’s not unusual for 15 or more to appear at once. Canker sores are not contagious. They are very common, occurring predominantly among those between the ages of 10 and 40, especially women.

Canker sores usually heal within two weeks, but they may recur. Although they pose no serious health threat, severe canker sores can make eating and talking unpleasant.

What Causes Canker Sores?

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, malnutrition and certain vitamin and mineral deficiencies may be associated with canker sores.
  • Often canker sores occur spontaneously.

Symptoms of Canker Sores

  • Small, painful, white or gray, crater-like, red-rimmed ulcers located anywhere inside the mouth, including the gums, tongue, and lips. Ulcers may appear singly or in groups.

Canker Sore Prevention

  • Brush and floss your teeth regularly.
  • Try to determine if certain foods seem to trigger canker sores and then avoid those foods.
  • Avoid chewing gum and eating hard, crunchy or spicy foods.
  • Don’t use a mouthwash that contains alcohol. Instead, try a rinse like Dentyl that's alcohol-free and adheres to and removes bacteria from the mouth.

Diagnosis of Canker Sores

  • 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.

How to Treat Canker Sores

  • 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 recurrent or more severe ulcers, a doctor may recommend using an antiseptic mouthwash. In addition, a doctor may prescribe topical anesthetics or corticosteroids to reduce symptoms and inflammation, and to speed healing.
  • Apply a mixture of equal parts water and hydrogen peroxide directly to the sore, followed by a small amount of milk of magnesia to relieve discomfort and promote healing.
  • Some doctors recommend applying wet black tea bags to the sores. Black tea contains tannin, which may help relieve pain.

When to Call a 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.
  • Call your doctor if the ulcers persist for longer than two weeks despite treatment.


Johns Hopkins Symptoms and Remedies: The Complete Home Medical Reference

Simeon Margolis, M.D., Ph.D., Medical Editor

Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50

Updated by Remedy Health Media

Publication Review By: the Editorial Staff at HealthCommunities.com

Published: 04 Oct 2011

Last Modified: 04 Nov 2014