Canker Sores

Overview

What are canker sores?

Canker sores are small shallow ulcers that occur in the lining of the mouth. The medical term for canker sores is “aphthous ulcers.” Canker sores start as white to yellowish ulcers that are surrounded by redness. They're usually very small (less than 1 mm) but may enlarge to ½ to 1 inch in diameter. Canker sores can be painful and often make eating and talking uncomfortable. There are two types of canker sores:

  • Simple canker sores: These may appear three or four times a year and last up to a week. Anyone can get canker sores but they typically occur in people between ages 10 and 20.
  • Complex canker sores: These are less common and occur more often in the people who have previously had them.

Symptoms and Causes

What causes canker sores?

The exact cause of most canker sores is unknown. A stress or minor injury to the inside of the mouth is thought to be the cause of simple canker sores. Certain foods —including citrus or acidic fruits and vegetables (such as lemons, oranges, pineapples, apples, figs, tomatoes, strawberries) — can trigger a canker sore or make the problem worse. Use of nonsteroidal anti-inflammatory drugs, like ibuprofen (Advil®, Motrin®), is another common cause. Sometimes a sharp tooth surface or dental appliance, such as braces or ill-fitting dentures, might also trigger the sores.

Some cases of complex canker sores are seen in patients with diseases of the immune system. These diseases include lupus, Behcet's disease, inflammatory bowel diseases (including celiac disease, ulcerative colitis and Crohn’s disease) and AIDS. Canker sores are also seen in patients with nutritional problems, such as a deficiency in vitamin B-12, zinc, folic acid or iron.

What are the symptoms of canker sores?

You may have a canker sore if you have:

  • A painful sore or sores inside your mouth — on the tongue, soft palate (the back portion of the roof of your mouth) or inside your cheeks.
  • A tingling or burning sensation prior to the appearance of the sores.
  • Sores in your mouth that are round, white, or gray in color, with a red edge or border.

In severe attacks, you may also experience:

Diagnosis and Tests

Are cold sores the same thing as canker sores?

No. Although these sores are often confused for each other, they are not the same. Cold sores, also called fever blisters or herpes simplex type 1, are groups of painful, fluid-filled blisters. Cold sores are caused by a virus and are extremely contagious. Canker sores are not caused by an infection and so are not contagious. Also, cold sores typically appear outside the mouth — usually, under the nose, around the lips or under the chin, while canker sores occur inside the mouth.

Management and Treatment

How are canker sores treated?

Pain from a canker sore generally lessens in a few days and the sores usually heal without treatment in about a week or two. Simple over-the-counter products, such as Kank-A®, Zilactin® or Orajel®, can be taken to ease symptoms.

Sores that are large, painful, or don’t heal before new ones appear may be treated with a prescription antibacterial mouth rinse, a corticosteroid ointment or a prescription or nonprescription solution to reduce the pain and irritation.

Prevention

Can canker sores be prevented?

Although there is no cure for canker sores and they often recur, you may be able to reduce their frequency by:

  • Avoiding foods that irritate your mouth, including acidic, hot or spicy foods.
  • Avoiding irritation from gum chewing.
  • Brushing with a soft-bristled brush after meals and flossing daily. This will keep your mouth free of foods that might trigger a sore.
  • Avoiding oral hygiene products containing sodium lauryl sulfate.

You should call your doctor or dentist if you have:

  • Unusually large sores.
  • Sores that are spreading.
  • Sores that last three weeks or longer.
  • Intolerable pain despite avoiding trigger foods and taking over-the-counter pain medication.
  • Difficulty drinking enough fluids.
  • A high fever with the appearance of the canker sore(s).

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Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy