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Canker Sore Treatment Options, Symptoms, and Causes

March 20th, 2023 | 4 min. read

By Kathleen Rose McDonald, MD

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Unlike herpes simplex-1, which appears on the outside of one’s mouth, canker sores appear inside the mouth and may range in size. These sores often form in a round or oval shape and are generally not a cause for concern as they tend to heal themselves within two weeks. 

However, the presence of canker sores can make daily tasks more difficult, like brushing teeth, eating, or talking, due to the pain and discomfort that comes along with them. Some people experience chronic canker sores, and, therefore, look for causes, prevention, and treatment options.

What is a canker sore?

Canker sores, medically referred to as Aphthous ulcers, are shallow sores that appear in the tissue lining the mouth. Canker sores may appear on the lips, gums, beneath the tongue, on the roof of your mouth, and on the cheeks. 

These ulcers often begin as a small, white, or yellow-white circle that is clearly defined with a red border. While canker sores are often small in size, they can grow up to one inch in diameter and are quite painful regardless of size.

There are two primary canker sore types:

  • Simple canker sores are typically small in size, and can appear up to four times per year. They tend to heal themselves, without treatment required, within two weeks of appearing. Simple canker sores do not tend to leave scarring once healed. Minor canker sores account for about 80% of all canker sores. 

  • Complex canker sores are not as prevalent as simple canker sores, and are much larger in size than them as well. Complex canker sores are significantly more painful than the simple variety, and can take up to six weeks to fully heal, and are more likely to leave scarring. Complex canker sores comprise about 15% of canker sores.

Less common, making up about 5% of all canker sores, hepetiform canker sores seem to develop later in life, and their cause is largely unknown.


What are canker sore symptoms?

The most common symptom of a canker sore is the presence of a small, round, or oval-shaped ulcer that has formed inside the mouth. Some people may experience a painful burning or tingling sensation in the days leading up to the formation of a canker sore; however, this is not the case for all. 

Minor canker sores, the most commonly experienced type of canker sore, are typically smaller in diameter and oval-shaped with a red border whereas major canker sores are much larger and deeper, are round in shape, and have very defined borders or irregular edges.

Less common are herpetiform canker sores. These types of canker sores only affect about 5% of people who experience canker sores and may be accompanied by a tingling or burning sensation inside the mouth, pain, and small clusters of pinpoint-sized bumps inside the mouth.


What are the causes of canker sores?

The cause of canker sores is not fully understood yet in the medical community. However, there are many things that can trigger a canker sore including:

  • Emotional stress
  • A minor injury, including a sports injury or direct contact injury, a minor injury during dental work, or even biting your cheek or the inside of your lip
  • Using toothpaste or oral rinse that contains sodium lauryl sulfate
  • An allergic reaction to bacteria inside the mouth
  • Hormone changes, especially during menstruation in women
  • Wearing braces
  • Sensitivity to certain foods like coffee, nuts, and strawberries
  • Deficiencies in vitamin B12, vitamin B6, zinc, iron, and folic acid (folate)
  • Receiving chemotherapy

For some, certain diseases or medical conditions may cause canker sores like:

  • Celiac disease causes intestinal disorders due to heightened sensitivities to gluten - a protein found in nearly all grains. People with Celiac disease tend to live on a gluten-free diet to control symptoms.
  • Inflammatory bowel diseases including ulcerative colitis, and Crohn’s disease, are caused by constant inflammation of the digestive tract.
  • Behcet’s disease is a rare disease process that causes inflammation to occur throughout the entire body. This inflammation may irritate the lining of the mouth and cause canker sores.
  • HIV and AIDS are two immune-suppressing diseases whereby individuals may be more prone to developing canker sores.
  • Having an immune system that attacks healthy cells.

It is important to remember that canker sores are not sexually transmitted diseases or sexually transmitted infections, are not contagious, and are not spread through contact or kissing.


What are the treatment options for canker sores?

There are no invasive or extensive tests required to diagnose a canker sore. These ulcers can be easily diagnosed through a visual examination by yourself, your primary care provider, or your dentist. Canker sores generally do not raise concern for health providers as they are easily treated at home and heal themselves. While treatment is not always necessary for minor canker sores, your doctor may recommend the following for persistent canker sores or major canker sores:

Mouth rinses

If you have several small canker sores or a complex canker sore, your doctor may prescribe a mouth rinse containing dexamethasone - a steroid used to reduce inflammation and relieve pain. These rinses are often used two to three times a day and promote healing in just a few days.

Topical medication

Whether over-the-counter or prescription, topical products can help to alleviate pain and promote a quicker recovery. Topical products used to treat canker sores include paste, gels, creams, and liquid products like Benzocaine, hydrogen peroxide, and Fluocinonide.

Oral medication

Unlike topical products that are placed directly on the canker sore, oral medications are used for stubborn canker sores or large sores that do not heal within two weeks. Oral medications may be given in liquid or pill form and may include antibiotics or oral steroids like Sucrulfate and Colchicine.


A chemical substance or electrical instrument may be used to cauterize a canker sore to destroy the tissue. While this sounds harsh, it is a rather pain-free procedure that is done in your health provider's office with no downtime required. It helps to reduce the time it takes a canker sore to heal by up to one full week and can help to relieve pain.

Nutritional changes

If you experience frequent canker sores due to a diet that is lacking certain vitamins and nutrients, your healthcare provider may recommend adding vitamin supplements into your daily routine. Vitamins that may lead to canker sores include vitamin B6, vitamin B12, folic acid, and zinc.


Can canker sores be prevented?

Practicing good oral hygiene habits is one of the best things you can do to help to prevent canker sores. This involves consistently brushing your teeth after meals and flossing at least once per day. To prevent irritation to the delicate tissues of your mouth, use a soft toothbrush. 

Also, avoid mouth rinses and toothpaste that contain sodium lauryl sulfate, which can promote the development of canker sores in people who are prone to getting them.  Sodium lauryl sulfate

Is a foaming agent and surfactant which can make your mouth seem cleaner with its foamy, bubbling action. However, it can strip away the protective lining of the mouth, making tissues more conducive to canker sores. 

Other things you can try are drinking through a straw and avoiding eating and drinking acidic foods and beverages, such as tomatoes and orange juice. 


Treating Canker Sores at Houston ENT & Allergy

For Houston Ear, Nose, Throat, and Allergy, patient care has been the first priority. Our team specializes in treating ENT and allergy conditions, including hearing and balance disorders, sleep apnea, and snoring, as well as canker sores. Treating a variety of conditions from an ear infection in children to cosmetic facial plastic surgery in adults, Houston Ear, Nose, Throat, and Allergy provides a comfortable environment to treat the whole family.

Schedule your canker sore treatment appointment today. 


Kathleen Rose McDonald, MD