Information About these Sometimes Painful Oral Nuisances and How to Prevent Them

Canker sores, also called aphthous ulcers, are small, shallow lesions that develop on the soft tissues in your mouth or at the base of your gums. They can be painful and can make eating and talking difficult.

Young woman having toothache

Although anyone can develop canker sores, they occur more often in teens and young adults, and they’re more common in females. Often people with recurrent canker sores have a family history of the disorder. This may be due to heredity or to a shared factor in the environment, such as certain foods or allergens.

What are the Symptoms of Canker Sores?

Most canker sores are round or oval with a white or yellow center and a red border. They form inside your mouth — on or under your tongue, inside your cheeks or lips, at the base of your gums, or on your soft palate. You might notice a tingling or burning sensation a day or two before the sores actually appear.

There are several types of canker sores, including minor, major and herpetiform sores.

Minor Canker Sores

Minor canker sores are the most common and:

  • Are usually small.
  • Are oval shaped with a red edge.
  • Heal without scarring in one to two weeks.

Major Canker Sores

Major canker sores are less common and:

  • Are larger and deeper than minor canker sores.
  • Are usually round with defined borders, but may have irregular edges when very large.
  • Can be extremely painful.
  • May take up to six weeks to heal and can leave extensive scarring.

Herpetiform Canker Sores

Herpetiform canker sores are uncommon and usually develop later in life, but they’re not caused by herpes virus infection. These canker sores:

  • Are pinpoint size.
  • Often occur in clusters of 10 to 100 sores, but may merge into one large ulcer.
  • Have irregular edges.
  • Heal without scarring in one to two weeks.


What Causes Canker Sores?

The precise cause of canker sores remains unclear, though researchers suspect that a combination of factors contributes to outbreaks, even in the same person.

Possible triggers for canker sores include:

  • A minor injury to your mouth from dental work, overzealous brushing, sports mishaps or an accidental cheek bite.
  • Toothpastes and mouth rinses containing sodium lauryl sulfate.
  • Food sensitivities, particularly to chocolate, coffee, strawberries, eggs, nuts, cheese, and spicy or acidic foods.
  • A diet lacking in vitamin B-12, zinc, folate (folic acid) or iron.
  • An allergic response to certain bacteria in your mouth.
  • Helicobacter pylori, the same bacteria that cause peptic ulcers.
  • Hormonal shifts during menstruation.
  • Emotional stress.
  • A sharp tooth surface or dental appliance, such as braces or ill-fitting dentures, might also trigger canker sores.

Canker sores may also occur because of certain conditions and diseases, such as:

  • Celiac disease, a serious intestinal disorder caused by a sensitivity to gluten, a protein found in most grains.
  • Inflammatory bowel diseases, such as Crohn’s disease and ulcerative colitis.
  • Behcet’s disease, a rare disorder that causes inflammation throughout the body, including the mouth.
  • A faulty immune system that attacks healthy cells in your mouth instead of pathogens, such as viruses and bacteria.
  • HIV/AIDS, which suppresses the immune system.


Are Cold Sores and Canker Sores the Same Thing?

No. Although cold sores and canker sores are often confused with each other they are not the same. Canker sores don’t occur on the surface of your lips and they aren’t contagious like cold sores. Unlike cold sores, canker sores are not associated with herpes virus infections. Cold sores, also called fever blisters or herpes simplex type 1, are groups of painful, fluid-filled blisters. 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.


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.

If sores are large, painful, or persistent, your dentist may prescribe an antimicrobial mouth rinse, a corticosteroid ointment, or a prescription or over-the-counter solution to reduce the pain and irritation.

You should call your dentist about canker sores if you have:

  • Unusually large sores.
  • Sores that are spreading.
  • Sores that last 3 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 sores.


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:

  1. Avoiding foods that irritate your mouth, including citrus fruits, acidic vegetables, and spicy foods.
  2. Avoid foods that cause the symptoms of an allergy, such as an itchy mouth, a swollen tongue, or hives.
  3. Avoiding irritation from gum chewing.
  4. Brushing with a soft-bristled brush after meals and flossing daily, which will keep your mouth free of foods that might trigger a sore.
  5. If your canker sores pop up due to stress, you can use stress reduction methods and calming techniques, such as deep breathing and meditation.

Talk with your doctor to determine if you have any specific vitamin or mineral deficiencies. They can help design a suitable diet plan and prescribe individual supplements if you need them.

Sources: Mayo Clinic, WebMD,