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Test Your Knowledge of Canker Sores

What Are Canker Sores?

Recurrent aphthous stomatitis, also known as “canker sores,” is an illness that causes small ulcers to appear in the mouth, usually inside the lips, on the cheeks, or on the smooth surfaces of the undersides of the tongue.

What Causes Them?

The exact cause of canker sores is not known. There are many factors that are thought to be involved with the development of canker sores, including:

  • Immune system problems

  • Allergies to food such as nuts, wheat products (gluten), various fruits or chocolate

  • Stress or fatigue

  • Viruses and bacteria

  • Trauma to the mouth

  • Poor nutrition

  • Certain medications

  • Systemic conditions such as Crohn’s disease

  • Using toothpaste containing sodium lauryl sulfate

Canker sores are not contagious and cannot be spread. Canker sores are usually seen in individuals before they reach age 20. Although severity and recurrence rates vary from patient to patient, approximately 80 percent of individuals suffer from the more minor form of this condition.

What Are the Signs and Symptoms?

The following are the more common signs and symptoms for the minor form of this condition. However, other conditions may cause ulcers in the mouth, so any ulcer lasting more than 10 to 14 days warrants consultation with a dental professional:

  • Ulcers less than 1 centimeter in diameter in the mouth, usually inside the lips, on the cheeks, or on the tongue

  • Ulcers that are covered with a gray, white or yellow layer and have a red border

  • Ulcers that usually heal in seven to 14 days and do not cause scarring

  • Ulcers that may reappear

How Are Canker Sores Diagnosed?

Diagnosis is usually based on a physical exam and complete medical history. The appearance and location of the sores are helpful in identifying this condition. In addition, your dental professional may order the following tests to help confirm the diagnosis and rule out other causes for the mouth ulcers:

  • Blood tests

  • Cultures of the ulcers

  • Biopsy of the sore—taking a small piece of tissue and examining it microscopically

How Are Canker Sores Treated?

The goal of treatment is to help decrease the severity of the symptoms, help with healing, and prevent recurrence. Treatment for minor canker sores may include:

  • Over-the-counter topical anesthetics

  • Antimicrobial mouthrinses

  • Avoiding hot, spicy or acidic foods

If outbreaks are frequent and/or severe, consultation with a dental professional and perhaps other medical professionals may be in order. For more major cases, treatment focuses on providing relief for symptoms. Topical analgesics, such as benzocaine, may be used. Prescription drugs, such as topically delivered glucocorticosteroids, may help with disease containment. Keeping an ulcer diary may also help identify connections between canker sore outbreaks and diet, hygiene habits (certain toothpastes) or lifestyle (stress). Sharing this information with your dental professional may help you devise more effective prevention and treatment strategies.

“Mouth Sores.” American Dental Association. Accessed 2013.

“Patient Information Sheet: Canker Sores (Recurrent Aphthous Stomatitis [RAS]). American Academy of Oral Medicine, December 31, 2007. Accessed 2013.

“Oral Mucosal Diseases in the Office Setting – Part I: Aphthous Stomatitis and Herpes Simplex Infections.” J.J. Sciubba. General Dentistry. July/August 2007, vol. 55, no. 4, pp. 347-54. Abstract: Accessed 2013.

“Canker Sore." Mayo Clinic. Accessed 2013.

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