Canker Sores

Canker Sores Health Summary
Canker sores (aphthous stomatitis) are among the most common causes of sores in the mouth. Causes of canker sores include heredity, oral trauma, hormonal changes, anxiety, stress, quitting smoking, medications, food allergies, toothpastes, and certain diseases. Symptoms of canker sores include painful but clear sores, deep painful ulcers, and herpetiforms. Treatment of canker sores include medication and herbal supplements.
Medical Author:
Medical Editor:

Canker Sore Overview

Canker sores, also known as aphthous ulcers, are among the most common causes of painful sores in the mouth.

  • The classic lesion is a small (less than 1 centimeter) oval to round ulcer with a erythematous (red) border. They occur on the mucous membranes inside the mouth.


  • From 20%-40% of the U.S. population have them at some point in their lives, and many people with have multiple episodes of them. Unless it is a recurrent problem, no workup or treatment is really needed.


  • The peak incidence occurs among people in adolescence and young adulthood. They become less frequent as we get older.


  • They occur more frequently in whites, nonsmokers, and people with higher socioeconomic status.


  • They are not contagious.


  • Canker sores are not the same thing as cold sores. Cold sores ("fever blisters") occur on the outer lip, whereas canker sores are found inside the mouth.

Canker Sore Causes

No one knows what causes canker sores. The vast majority of people who develop canker sores do not have another problem as the cause.

  • Both hereditary and environmental causes of the disease have been suggested, but the exact cause is not clear.


  • A number of factors have been suggested to precipitate outbreaks in susceptible individuals; however, none has been proven to be the cause in all people.


    • oral trauma


    • hormonal changes related to the menstrual cycle


    • anxiety or stress


    • smoking cessation


    • heredity


    • drugs (including anti-inflammatory drugs, such as ibuprofen [Motrin], and beta-blockers, such as atenolol [Tenormin])


    • food allergies or sensitivities (chocolate, tomatoes, nuts, and acidic foods such as pineapple, and preservatives such as benzoic acid and cinnamaldehyde)


    • toothpastes containing sodium lauryl sulfate


    • deficiencies of iron, folic acid, or vitamin B12 (although supplementation with iron or vitamins has not been shown to decrease the likelihood of ulcer resolution)


  • Some studies have suggested an association with Helicobacter pylori, the same bacteria that cause peptic ulcers. Recent studies have suggested that treatment of the Helicobacter pylori infection may improve symptoms or completely stop recurrent disease in some patients.
  • Recurrent canker sores have been associated with inflammatory bowel diseases, such as Crohn disease and ulcerative colitis. In these cases, the development of canker sores may signal a flare-up of the bowel disease.


  • Celiac, or abdominal, sprue, a disease of the intestines caused by sensitivity to gluten, causes malabsorption and is associated with development of canker sores. Gluten refers to a group of proteins found in wheat, barley, and rye.


  • Behçet's disease is a condition characterized by canker sores, genital sores that resemble canker sores, and inflammation of the eye.


  • Infection with the AIDS virus also has been associated with canker sores.


  • It is a common misconception that canker sores are a form of herpes infection. This is not the case.

Patient Comments

Viewers share their comments

Canker Sores - Effective Treatments Question: Please describe what treatments have been effective for your canker sores.
Canker Sores - Symptoms and Signs Question: What symptoms and signs did you experience with canker sores?

STAY INFORMED

Get the Latest health and medical information delivered direct to your inbox!