What are Canker Sores?

Last Updated: June 2007

What are canker sores?

Canker sores are mouth ulcers. Other medical terms used to refer to canker sores are "minor aphthous ulcers" and "recurrent minor aphthous stomatitis." Canker sores are the most commonly occurring type of mouth ulcer.

The term "canker" is a derivative of the Latin word "cancer." But aphthous ulcers are not a type of cancer.

Aphthous ulcers may be confused with other types of lesions that have names sounding similar to the word "canker." A "chancre (shang'ker) sore" is a type of lesion that is associated with the disease syphilis, and these sores are not related to aphthous ulcers.

The terms "cankor" and "kankor" seem to be common misspellings of the word "canker" and thus should typically be considered to be a reference to aphthous ulcers.

What causes canker sores?

The exact trigger by which canker sores form has not yet been determined but it is likely that their development is related to a reactions in an individual's immune system.

Canker sores are thought to form when, for unexplained reasons, a person's immune system identifies the presence of chemical molecules that it does not recognize. The presence of these molecules activates an attack by the immune system's lymphocytes (a type of white blood cell), somewhat similar as when a person's immune system attacks a transplanted organ. The disruption created by these lymphocytes' attacking unrecognized molecules results in the formation of mouth ulcers. We term these ulcers canker sores.

What triggers canker sores?

Many factors that seem to be triggers of canker sores have been identified. Any one or a combination of the following items may play a role in the formation of canker sores for any individual:

• Toothpastes and mouthwashes that contain sodium lauryl sulfate.
  Research suggests that the use of products that contain sodium lauryl sulfate ("SLS"), a foaming agent found in many toothpaste and mouthwashes, they can be associated with an increased recurrence rate of canker sores for an individual. This may be due to a drying effect SLS has on the epidermal surfaces of oral tissue. After this protective layer is compromised the tissue underneath is more vulnerable to acidic foods.

• Mechanical effect.
  A physical trauma preceding the formation of canker sores may play a role. This trauma might be in the form of a self-inflicted bite, irritation from a sharp or broken tooth, or possibly from some type of food such as a hard chip. 40% of the clients of one study felt that their canker sores were a result of trauma.

• Emotional effect.
  Psychological stress can be shown to adversely affect the health of people in many ways. Several people who suffer from canker sores report that appearances of their ulcers coincide with periods of uncertainty.

• Nutritional defects.
  Researchers also suggest that some individuals suffering from canker sores have underlying nutritional deficiencies. Some of the deficiencies correlated with the presence of canker sores are:

  • Deficiencies in: B1, B2, B6, B12, C
  • Lacking nutrients: zinc, folic acid, iron, selenium, calcium

• Allergies effect.
  Allergies to foods and other substances ingested have been identified as triggers for canker sore breakouts. Any substance that comes into contact with the person's oral tissues are considered to be causative agents. If allergies are suspects the individual might choose to create a journal to help them (and their dentist) identify the most likely irritant attributed to their sores. In extreme cases allergy testing might be perscribed.

  Some foods identified as being potential triggers for canker sores are:

  • Grains: buckwheat, wheat, oats, rye, barley, gluten found in grains
  • Acidic fruits and vegetables: lemons, oranges, pineapples, apples, figs, tomatoes, strawberries
  • Dairy: milk, cheeses
  • Others: nuts, chocolate, shellfish, soy, vinegar, French mustard
  • Additives: cinnamonaldehyde (flavoring), benzoic acid (preservatives)
  • Other than foods: toothpastes, mints, gums, dental materials, metals, medications

• Hormonal effects.
  Some women have suggested that they find a relationship of canker sores and certain phases of their menstrual period. It’s been reported that a woman may notice remission/secession of canker sores during pregnancy. There is no definitive research that confirms these affects.

• Genetic effects.
  Some researchers have identified a genetic predisposition for canker sores. One study finds that 35% of those persons who experience canker sores have at least one parent who suffers from these ulcers. Another study identified that almost 91% of identical twins both suffered from canker sores whereas only 57% of fraternal twins did.

• Infectious agents.
  The fact that compounds typically associated with bacterial and viral infections that have been isolated from canker sores suggests that bacteria or viruses could be agents directly attributed to the formation of these ulcers.

• Medical conditions.
  Several medical conditions can be associated with the presence of canker sores. Those patients who experience persistent canker sores must consider the presence of an underlying undiagnosed disease/condition and the need for a more in-depth evaluation by a physician.

  Some medical conditions that have been associated with the presence of mouth ulcers are: Behcet's disease, neutrophil dysfunction diseases, irritable bowel diseases, and HIV-AIDS.

• Medications.
  The use of nonsteroidal anti-inflammatory drugs (NSAIDs), beta blockers, chemotherapeutic agents, and nicorandil have each been reported as triggers of canker sores.