New Research Brings New Understanding to Canker Sore Causes

Canker sore sufferers take note: Swedish researchers have uncovered a new cause for these painful ulcers which may open the door to new treatments. Researchers at the Sahlgrenska Academy at the University of Gothenburg in Gothenburg, Sweden, have found that canker sores are likely caused by bacteria flora in the mouth. Other possible causes include food allergies or genetics. Â?

Canker sores are small, shallow ulcers that appear in the mouth, and are medically known as recurrent aphthous stomatitis. Canker sores affect over half the population of the United States, according to the American Academy of Oral Medicine, and are the most common type of oral lesion in the world.

Canker sores usually appear as a white blister, with a red ring around it. They usually occur on the inside of the cheeks, lips, on either side of the tongue and in the throat.

Types of canker sores

There are two types of canker sores; simple canker sores and complex canker sores. Simple canker sores occur just a few times per year and last about only about a week for most individuals. They are painful, but in most cases tolerable.

Complex canker scores are less common than simple canker sores but are larger and more painful than simple canker sores. Complex canker sores often leave scars in the mouths of sufferers. Patients that suffer from complex canker sores have more outbreaks than their peers with simple canker sores.

For years, one of the primary causes of canker sores was thought to be a virus, and the condition was treated similarly to cold sores with antiviral medicines. Part of the reason for this is that canker sores are hard to distinguish from cold sores. Other causes though to be behind these painful ulcers included a weakened immune system, hormonal changes brought on by menstruation and vitamin deficiency.

Canker sores have long been thought as an illness, rather than a medical issue. While the most predominant symptom of canker sores is pain at the site of the ulcer, many patients also experience fatigue, fever and swollen lymph nodes.

What Researchers Say About Canker Sores

Researchers on the Swedish study hesitate to call canker sores a true illness, but rather an indicator of something else going on with the body, like good and bad bacteria out of balance in the mouth. During the study, researchers found higher levels of illness-causing bacteria in study participants with canker sores than participants without.

“Canker sores are very painful for many patients, and the pain of the ulcer often prevents sufferers from eating or even talking normally,” Dr. James Erpenbach, D.D.S., said.

Erpenbach is a Knoxville, Tennessee, dentist who often encounters patients with canker sores during regular cleanings and checkups.

“Canker sore patients frequently just live through the pain until the sore goes away, which happens about a week or ten days after onset,” Erpenbach said.

Erpenbach advises canker sore patients to discuss their condition and symptoms with their dentist at regular checkups, but patients experiencing prolonged canker sores should make an appointment sooner rather than later.

“If patients have mouth sores that do not resolve with or without medical interventions within two weeks, patients should visit their dentist to determine if a lesion or ulcer needs a closer look,” Erpenbach said.

Erpenbach also urges patients to see the dentist if sores are larger than one centimeter wide, sores appear more frequently than before and more sores are appearing than previously experienced. Patients should also be seen if their cold sores are accompanied by a rash, joint pain, fever or diarrhea.

Although there is currently no cure for canker sores, there are treatments for the symptoms of the sores such as pain relievers and topical analgesic gels to numb the afflicted area. The study may lead researchers to develop antibiotic regimens to treat the illness causing bacteria is believed to cause the lesions.


University of Gothenburg. “New research comes to terms with old ideas about canker sores.” ScienceDaily. ScienceDaily, 29 March 2017.

American Academy of Oral Medicine. “Canker Sores”