The Different Types of Canker Sores

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What exactly are canker sores, and what are the different types? What are the symptoms, causes, and treatments?

Canker sore on woman's upper lip
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Canker sores, also known as aphthous ulcers or aphthous stomatitis, are small lesions (sores) that occur inside of the mouth. The exact cause is unknown but they are not contagious.

Roughly 20% of people will develop canker sores at some time in their life, and the condition appears to run in families. Canker sores do not develop on the external surfaces of the lips and are not to be confused with cold sores.

Types of Canker Sores

Not all canker sores are alike. Canker sores may be classified as minor, major, or herpetiform.


Although painful, minor canker sores are often fully healed within two weeks after onset. The size of a minor canker sore varies but typically stays under 1/3 inch to 1/2 inch. Minor canker sores may also be referred to as "simple" canker sores. The relative incidence of this type of sore is 80%.


Canker sores that appear larger than 1/3 inch to 1/2 inch, usually last longer than two weeks, and appear to have irregular, oddly-shaped margins. Rarely, this type of canker sore may leave behind a scar.

Major canker sores are common in people who are immunosuppressed due to chemotherapy or a condition such as HIV/AIDS. Major canker sores may also be referred to as "complex" canker sores. These account for 15% of canker sores.

Herpetiform Canker Sores

As a cluster of several (often dozens) of tiny lesions that appear to form one larger sore, herpetiform canker sores may last from one week to one month. These represent 5% of canker sores.

Canker Sore Symptoms

Canker sores appear inside of the mouth as round or oval sores typically with a red border and yellow, gray, or white center. Canker sores typically develop:

  • On the top surface of the tongue and the tip of the tongue
  • Underneath the tongue, on the floor of the mouth
  • The inside of the cheek and lip
  • On the gum tissue

One to two days before appearing visually, a burning or tingling sensation may be present in the area of your mouth where the lesion is developing. Rarely, a fever might be present when developing a canker sore.

Canker sores may become quite painful, especially when eating, drinking, and talking.


While we don't know exactly what causes canker sores, several risk factors have been identified. Any form of trauma to the mouth, from sports injuries, to eating hot food, and even some ingredients in toothpaste may result in canker sores. Canker sores are also more common in people with certain vitamin deficiencies or who are immunosuppressed.


Canker sores do not necessarily need to be treated, and even if they do, they may respond to simple at-home remedies such as a saltwater and sodium bicarbonate solution. When severe, prescription medications may be needed.

It is recommended that you seek treatment from your dentist if you have recurrent canker sores and/or canker sores that do not heal after 14 days.

One of the best ways to avoid canker sores is to treat the underlying causes. Improperly fitting dentures or broken teeth should be repaired. If it is hot or spicy food, or even gluten in food if you have celiac disease, making dietary changes may help.

Even stress management techniques may be of some benefit as stress appears to trigger canker sores for some people. Some potential causes are unavoidable, but you may wish to talk to your healthcare provider if you are experiencing recurrent canker sores related to a medical condition.

Frequently Asked Questions

How do you treat a major canker sore?

If your canker sore is large and painful, your healthcare provider may prescribe an antibacterial mouth rinse or a corticosteroid ointment. Over-the-counter oral pain gels are also available to help ease symptoms.

How long does it take a major canker sore to heal?

Major canker sores can take between four and six weeks to heal. They may also leave a scar.

A Word From Verywell

Canker sores can be uncomfortable and make it difficult to eat, or even talk. There are different types of canker sores, which are in turn related to different risk factors. Most of the time canker sores do not need to be treated, but home remedies, as well as prescription treatments, are available if needed.

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Article Sources
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  1. Edgar, N., Saleh, D., and R. Miller. Recurrent Aphthous Stomatitis: A Review. Journal of Clinical and Aesthetic Dermatology. 2017. 19(3):26-36. PMID: 28360966

  2. Ziaudeen, S., and R. Ravindran. Assessment of Oxidant-Antioxidant Status and Stress Factor in Recurrent Aphthous Stomatits Patients: Case Control Study. Journal of Clinical and Diagnostic Research. 2017. 11(3):ZC01-ZC04. doi: 10.7860/JCDR/2017/22894.9348

  3. Cleveland Clinic. Canker Sores.

Additional Reading
  • Weller, Richard P. J. B., Hamish J.A. Hunter, and Margaret W. Mann. Clinical Dermatology. Chichester (West Sussex): John Wiley & Sons Inc., 2015.

  • Edgar, N., Saleh, D., and R. Miller. Recurrent Aphthous Stomatitis: A Review. Journal of Clinical and Aesthetic Dermatology. 2017. 19(3):26-36.