What Causes Canker Sores?

mHave you ever wound up with an annoying little bump on your cheek or inside your lips after you accidentally bit inside your mouth? These obnoxious little sore, which your tongue may have a hard time ignoring, are known as canker sores. Canker sores, which are also known as aphthous ulcers, are small, shallow lesions that develop on the soft tissues in your mouth or at the base of your gums and can make eating or talking uncomfortable. Unlike cold sores, canker sores don’t occur on the surface of your lips and they aren’t contagious. 

Types of Canker Sores

There are several different types:

  • Minor canker sores
    • These sorts of sores are common and may show up several times throughout the year. They are typically small, oval-shaped, and have a red edge. They are most common in people between the ages of 10 and 20 and will usually heal without scarring in one to two weeks.
  • Major canker sores
    • Far less common than minor canker sores, these sores are typically bigger and can last for more than two weeks and leave behind extensive scarring. They’re usually round with defined borders but can have irregular edges when they’re larger. These can be extremely painful.
  • Herpetiform canker sores
    • This type is far less common and usually develops later on in life. Despite the name, they are not actually caused by the herpes virus. These appear in clusters of 10 to 100 sores, are often pinpoint in size, and sometimes merge into one larger ulcer. They also have irregular edges and can heal without scarring in one to two weeks. 


Although scientists aren’t entirely sure what exactly causes most canker sores, there are a number of things that may play a factor.

For minor sores, these include:

  • Stress
  • Tissue injury from a sharp tooth or dental appliance
  • Certain acidic fruits and vegetables
  • Nonsteroidal anti-inflammatory drugs like ibuprofen
  • Allergy to something like your food, toothpaste, or mouthwash. 

For complex sores:

  • Can be caused by an underlying health condition like a weakened immune system, HIV/AIDs, lupus, or Behcet’s disease.
  • Certain nutritional problems like a lack of vitamin B12, zinc, folic acid, or iron
  • Gastrointestinal diseases like celiac or Crohn’s.

Canker sores as a whole are relatively common, with about 1 in 5 people getting them regularly. They are more common in women, perhaps due to differences in hormones, and can even run in families.

Conclusion and when to see your dentist

Although most canker sores are completely harmless, there are some situations when it would be good to visit your dentist or general practitioner to have them examined. If the sores are unusually large, they recur frequently, lasts for more than two weeks, extend to the lips, cause pain you can’t control with self-care measures, cause difficulty with eating or drink, or you have a high fever alongside them, it’s necessary to have it checked by your doctor. 

We examine your entire mouth to ensure your oral health is sound. If you’re having issues with a troublesome canker sore, feel free to contact us and we can work with you to help resolve it.

Related Articles

Ready To Become A Patient?

Click or tap the button below to fill out a new patient form and we will be in touch. It’s that easy!