Canker Sores: Definition & Causes

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

In this lesson, you're going to learn about a very famous problem, canker sores. We'll look at some of the weird alternative names given to these sores and then explore the reasons for why they may occur.

Medical Lingo

Do you have recurrent aphthous ulcers? If not, have you ever had aphthous stomatitis? Say what, right? Don't be intimidated by those fancy words. They are nothing more than medical terms for something you've surely heard of: canker sores. Let's first define canker sores and then figure out what may cause them.

What are Canker Sores?

Canker sores are typically small, shallow, non-contagious, and painful defects in the soft tissues of the inside of the mouth. They are commonly round or oval, white to yellow in color, and have a reddish border. Canker sores are also well-demarcated, meaning that they have clearly visible boundaries. They can appear alone or in multiples. While canker sores commonly go away within 1-2 weeks, the larger ones can last for months at a time. Canker sores can also recur (come back) every few days to every few months.

Note the white color and clearly visible boundaries of this canker sore.
Canker Sore

Canker sores are also called aphthous ulcers. The word 'aphthous' is derived from the Greek word for ulceration. So, in a way, when you say aphthous ulcer you're kind of saying 'ulcer ulcer'. This is sort of like saying 'desert desert' if you say 'The Sahara Desert', since Sahara already means desert.

Anyways, an ulcer is basically a sore in or of a body tissue. Canker sores may also be called recurrent aphthous stomatitis. Stoma- means mouth and -itis means inflammation. So the term literally means an ulcerative (sore-causing) inflammation of the mouth that comes back time after time.

Causes of Canker Sores

Luckily, this term gives away one key cause of the canker sores: inflammation. Biochemical factors released by your body's cells cause the inflammation of part of the inside of the mouth, resulting in a canker sore. Inflammation causes pain, redness, and swelling, all of which can be identified in a canker sore. While inflammation is a response that's supposed to kill dangerous foreign invaders, like bacteria, it's also indiscriminate. Meaning, it can also hurt your body's cells, including the ones in the mouth, resulting in canker sores.

The main question is: what triggers the inflammation? Possible triggers for the inflammation include:

  • Trauma to the mouth, like biting the inside of the lip or brushing a bit too vigorously
  • Stress, like after a really bad break-up
  • Certain foods, like chocolate, peanuts, coffee, almonds, eggs, cereals, cheese, tomatoes, and strawberries, as well as spicy and acidic foods. Seems like we can't eat anything, right?
  • Certain toothpastes or mouth rinses that contain a chemical called sodium lauryl sulfate, which may also cause the inside of your mouth to peel off overnight. Fun!
  • Not enough vitamin B-12, zinc, iron, or folic acid in the diet
  • Bacteria, including H. pylori, the bacterium responsible for peptic ulcers. This point is disputed, however.
  • Various diseases, such as celiac disease, Crohn's disease, ulcerative colitis, systemic lupus erythematotus, and Behcet's disease.

Lesson Summary

Canker sores are technically called aphthous ulcers or recurrent aphthous stomatitis. These are lesions (defects) inside the mouth. They have several characteristics. They are:

1. Typically small

2. Oval to round in shape

3. Shallow and well demarcated

4. White to yellow in color with a red, slightly raised, border (called a halo)

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