What Causes Chronic Canker Sores?

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

Do you get canker sores? And do you get them repeatedly over a long period of time? Then you may have chronic canker sores. Read on to discover the causes of these sores.

What Are Canker Sores?

Have you ever had a very painful, whitish looking, sore inside of your mouth? That may have been a canker sore, formally called an aphthous ulcer. These are usually small, round, and white defects in the mouth and they tend to be painful. Canker sores can, however, vary in size and they usually come back every now and then. Since they commonly recur, the condition of recurring canker sores is called recurrent aphthous stomatitis (RAS), where 'stomatitis' means inflammation of the mouth. Stoma- means mouth and -itis means inflammation.

What a canker sore may look like.
Canker sore

Because the sores come back repeatedly over a long period of time, this is a chronic condition. This is in contrast to an acute condition, one that is sudden in onset and of short duration.

Let's consider some of the reasons for why chronic canker sores occur.

Risk Factors For Canker Sores

In general, it's not entirely understood why some people get canker sores while others do not, let alone why some get them chronically. With that in mind, let's first go over some of the things that may predispose people to the formation of a canker sore.

For some people, trauma to the mouth may cause the appearance of canker sores. For instance, if they have a sharp-edged tooth that irritates their mouth or they have a habit of biting their gums or inside of their lips, this can lead to a canker sore. If you seem to get canker sores mainly around the time you're about to take a test, then your chronic canker sores might be due to stress. Hormonal changes have also been linked to RAS, such as those that occur during the menstrual cycle. And people who use a mouthwash or toothpaste containing an ingredient called sodium lauryl sulfate (SLS) may have that chemical compound to blame for the sores.

However, many of these causes are modifiable. For instance, a person can visit the dentist to take care of the tooth irritating the mouth. Someone using toothpaste with SLS can switch to another kind of SLS-free toothpaste. You get the idea. Yet, despite this, they may still have RAS. Thus, chronic canker sores may have a deeper component to them called genetics!


Your genes are pieces of code that make you who you are. They code for your body's form and function. If a piece of this code is poorly written, then like a piece of poorly written software code, something will malfunction. It is thought that people with chronic canker sores may have genetic factors predisposing them to the development of these sores on a recurrent basis. This is partly proven by the fact that some people with canker sores have a family history of canker sores.

Regardless, these genetic factors code for a partial malfunction of the immune system. The immune system is a collection of cells, biomolecules, and tissues that are supposed to protect you from disease-causing microbes like viruses and bacteria. However, if not properly coded, the immune system may act abnormally and predispose the person to getting chronic canker sores from what is, to another person, a completely harmless substance (like cow's milk). In essence, the immune system overreacts to the predisposing agent and causes canker sores as a sort of collateral damage.

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