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    Canker sore

    Aphthous ulcer; Ulcer - aphthous

    A canker sore is a painful, open sore in the mouth. Canker sores are white or yellow and surrounded by a bright red area. They are not cancerous.

    A canker sore is not the same as a fever blister (cold sore).


    Canker sores are a common form of mouth ulcer. They may occur with viral infections. In some cases, the cause is unknown.

    Canker sores may also be linked to problems with the body's immune system. The sores may also be brought on by:

    • Mouth injury from dental work
    • Cleaning the teeth too roughly
    • Biting the tongue or cheek

    Other things that can trigger canker sores include:

    • Emotional stress
    • Lack of certain vitamins and minerals in the diet (especially iron, folic acid, or vitamin B-12)
    • Hormonal changes
    • Food allergies

    Anyone can develop a canker sore. Women are more likely to get them than men. Canker sores may run in families.


    Canker sores usually appear on the inner surface of the cheeks and lips, tongue, upper surface of the mouth, and the base of the gums.

    Symptoms include:

    • One or more painful, red spots or bump that develops into an open ulcer
    • White or yellow center
    • Small size(most often under 1/3 inch across)
    • Gray color as healing starts

    Less common symptoms include:

    • Fever
    • General discomfort or uneasiness (malaise)
    • Swollen lymph nodes

    Painoften goes away in 7 to 10 days. It can take 1 to 3 weeks for a canker sore to completely heal. Large ulcers can take longer to heal.

    Exams and Tests

    Your health care provider can often make the diagnosis by looking at the sore.

    If canker sores persist or continue to return, tests should be done to look for other causes, such as erythema multiforme, drug allergies, herpes infection, and bullous lichen planus.

    You may needfurther testing or a biopsytolook for other causes of mouth ulcers.Canker sores are not cancer and do not cause cancer. There are types of cancer, however, that may first appear as a mouth ulcer that does not heal.


    In most cases, the canker sores go away without treatment.

    Try not to eat hot or spicy foods, which can cause pain.

    Use over-the-counter medicines thatease pain in the area.

    • Rinse your mouth with mild, over-the-counter mouthwashes or salt water.
    • Apply a mixture of half hydrogen peroxide and half water directly to the sore using a cotton swab. Follow by dabbing a small amount of Milk of Magnesia on the canker afterward. Repeat these steps 3-4 times a day.
    • Rinse your mouth with a mixture of half Milk of Magnesia and half Benadryl liquid allergy medicine. Swish mixture in the mouth for about 1 minute, then spit out.

    Medicines prescribed by your health care provider may be needed for severe cases. These may include:

    • Chlorhexidine mouthwash
    • Stronger medicines called corticosteroids that are placed on the sore or take in pill form

    Brush your teeth twice a day and floss your teeth every day. Also, get routine dental check ups.

    Outlook (Prognosis)

    Canker soresalmost alwaysheal on their own. The painshould decreasein a few days. Other symptoms disappear in 10- 14 days.

    When to Contact a Medical Professional

    Call your health care provider if:

    • A canker sore or mouth ulcer does not go away after 2 weeks of home care or gets worse.
    • You get canker sores more than 2 or 3 times a year.
    • You have symptoms with the canker sore such as fever, diarrhea, headache, or skin rash.


    Daniels TE. Diseases of the mouth and salivary glands. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011: chap 433.

    Chattopadhyay A, Shetty, KV. Recurrent Aphthous Stomatitis. Otolaryngological Clinics of North America. 2011;44(1)


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      • Mouth anatomy


      A Closer Look

        Talking to your MD

          Self Care

            Tests for Canker sore

              Review Date: 4/13/2013

              Reviewed By: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

              The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

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