What is a canker sore?

November 05, 2015


Your mouth is home to bacteria, plaque, saliva and, unfortunately, the occasional mouth sore. A plethora of circumstances can cause these oral lesions. Perhaps you scalded your tongue on a piping hot spoonful of soup. Maybe you bit your lip while munching on some carrots. One common type of dental wound in particular has a more complicated source: canker sores, otherwise known as aphthous stomatitis. A dental health professional can likely point these out and provide treatment options during your biannual visit, but you'll probably feel it in your mouth before then. It's important to recognize canker sores and find ways to alleviate the irritation at home. Use this guide to help: 

"You may experience some discomfort and irritation with canker sore."

What is a canker sore?
Minor canker sores typically appear as small white swellings surrounded by redness.1 Although rare, herpetiform canker sores may appear later in life and are marked by clusters of anywhere from 10 to 100 pinpoint-size sores.2

Canker sores may surface on the inside of your lips or cheeks, on the tongue, on the palate (the roof of your mouth) or the base of the gums.3 You may have just a single lesion, or you could experience several at once. These particular oral sores are not contagious.

There is not one known specific cause for canker sores, though researchers believe several combined biological and physical factors may be responsible for their development. These include the following:2

  • A minor oral injury, such as biting the inside of the cheek.
  • Hormonal changes due to menstruation cycles or stress.
  • Vitamin-deficient diets.
  • Sodium lauryl sulfate-containing toothpastes and mouth rinses.
  • Allergic reactions or food sensitivities.
  • Helicobacter pylori bacteria, which also cause peptic ulcers.

How do I know if I have a canker sore?
Beyond visibly noticing the canker sore in any of the aforementioned locations, you may experience some discomfort and irritation as well. Each of these lesions takes two to three days to develop, and you may feel a burning or tingling sensation at these beginning stages.3 It's not uncommon to worsen these symptoms by accidentally biting at the canker sore. After all, it is a raised surface in your mouth, and your bite alignment may not account for unexpected interference. As such, prevention and prompt treatment are pivotal.

How do I treat canker sores?
Canker sores typically heal on their own in a week or two. However, for particularly painful ones, topical ointments with active ingredients of benzocaine, hydrogen peroxide or fluocinonide may provide temporary relief. Otherwise, your doctor can prescribe a mouth rinse or medication to reduce pain.

You can help prevent canker sores by eating a diet high in vitamins B6 and B12 and zinc. Avoid consuming foods that are too hot or participating in activities that could lead to oral injury as well.

Girl blowing on spoonful of hot soup.
Make sure foods are cool enough to safely eat.

When to see a dentist
During your regular appointments, speak with your doctor about anything unusual you've experienced since your last visit, including the occurrence of a canker sore or any other oral lesion. Keeping your dental professional up to date on your oral well-being is important for maintaining a healthy smile. However, there are some situations in which you shouldn't wait until your scheduled appointment to bring up concerns.

If your canker sore does not go away within two weeks or is unusually large or painful, find a dentist and set up a visit. He or she may take a biopsy to determine if your canker sore really is that or if a more serious disease is to blame. Your mouth is often a window to your overall health, making regular consultations all the more important.


1. "What Are Canker And Mouth Sores?" Colgate, Nov. 15, 2010. http://www.colgate.com/en/us/oc/oral-health/conditions/mouth-sores-and-infections/article/what-are-canker-and-mouth-sores

2. "Canker Sore," Mayo Clinic, May 19, 2015. http://www.mayoclinic.org/diseases-conditions/canker-sore/basics/definition/con-20021262

3. "Canker Sores (Aphthous Stomatitis Or Recurrent Mouth Ulcers)," Colgate, Oct. 02, 2013. http://www.colgate.com/en/us/oc/oral-health/conditions/mouth-sores-and-infections/article/canker-sores-cold-sores-and-more


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