Canker Sores

Canker Sores

Canker sores are small ulcer craters in the lining of the mouth that are frequently painful and sensitive. Canker sores are very common. About 20% of the population (one out of five people) have canker sores at any one time. Canker sores are also medically known as aphthous ulcers or aphthous stomatitis.


Women are slightly more likely than men to have recurrent canker sores. It can occur at any age, but it is more commonly seen in teenagers. Genetic studies show that susceptibility to recurrent outbreaks of the sores is inherited in some patients. This partially explains why family members often share the condition.


Canker sores are generally classified into three groups based on size.


Minor sores have a diameter of 1 millimeter (mm) to 10mm. They are the most common (80% of all canker sores) and usually last about 7-10 days. 


Major sores (10% of all canker sores) have a diameter of greater than 10mm and they may take anywhere between 10-30 days to heal. They may leave a scar after they heal.


Herpetiform ulcers (10% of all canker sores) are formed by a cluster of multiple small individual sores (less than 3mm). They also usually heal within 7-10 days.


Canker sores are usually found on the movable parts of the mouth, such as the tongue or the inside lining of the lips and cheeks, and at the base of the gums. The ulcers begin as small oval or round reddish swellings that usually burst within a day. 


The ruptured sores are covered by a thin white or yellow membrane and edged by a red halo. Generally, the sores heal within two weeks without scarring. Fever is rare, and the sores are rarely associated with other diseases. Usually, a person has only one or a few canker sores at a time.


Most people experience their first bout with canker sores between the ages of 10 and 20. Children as young as 2 years old, however, can develop the condition. The frequency of canker sore recurrences varies considerably. Some people have only one or two episodes a year, while others may have a continuous series of canker sores.


The cause of canker sores is not well understood. More than one cause is likely, even for individual patients. Canker sores do not appear to be caused by viruses or bacteria, although an allergy to a type of bacterium commonly found in the mouth may trigger them in some people.


The sores may be an allergic reaction to certain foods. In addition, there is research suggesting that canker sores may be caused by a faulty immune system that uses the body's defenses against disease to attack and destroy the normal cells of the mouth or tongue.


British studies show that in about 20 percent of patients, canker sores are due partly to nutritional deficiencies, especially lack of vitamin B12, folic acid, and iron. Similar studies performed in the United States, however, have not confirmed this finding. In a small percentage of patients, canker sores occur along with gastrointestinal problems, such as an inability to digest certain cereals.


In these patients, canker sores appear to be part of a generalized disorder of the digestive tract. Vitamin C deficiency has also been associated with canker sores.


Emotional stress and local trauma or injury to the mouth, such as sharp metal braces, brushing with hard toothbrushes, and hot foods can lead to canker sores. Smoking and dentures can also contribute to the problem. Some studies have shown a connection with toothpaste containing sodium lauryl sulfate in some individuals, although, other studies have not found any connection.


Other possible causes of canker sores include illnesses in which the immune system causes swelling or inflammation of the body tissues (autoimmune disorders). Examples of autoimmune disorders are systemic lupus erythematosus, Crohn's disease, and Behçet's disease.


Female sex hormones also apparently play a role in causing canker sores. Many women experience bouts of the sores only during certain phases of their menstrual cycles. Additionally, most women experience improvement or remission of their canker sores during pregnancy. Researchers have usedhormone therapy successfully in clinical studies to treat some women.


Canker Sore Self-Care and Home Remedies


  • Try rinsing your mouth with a solution of ½ teaspoon salt dissolved in 8 ounces of water.
  • Another mixture that may be helpful consists of 1-2 tablespoons of Maalox mixed with ½ tablespoon of liquiddiphenhydramine (Benadryl). Swish a teaspoonful in your mouth and spit it out. This can be done four times a day. Make sure that you do not swallow the mixture, and be careful when using this remedy with children since the Benadryl can cause toxicity.
  • Some authors recommend the use ofcalamine (Calamox) lotion applied topically to the ulcer. However, this is an unapproved use and there are no controlled studies to support its safety or efficacy.
  • Liquids or ointments with a numbing ingredient such as benzocaine (Anbesol, Oragel, Orabase, Zilactin-B, Tanac) help relieve the discomfort of canker sores. It is important to be careful not to use more than the recommended amounts per day to avoid toxicity.


However, in April 2011 the U.S. FDA issued a warning about an association between benzocaine and methemoglobinemia, a rare but serious condition in which oxygen delivery to tissues is compromised. Because of this association, the FDA has stated that benzocaine products should not be used on children less than two years of age, except under the advice and supervision of a health care professional.


Further, adults who use benzocaine gels or liquids to relieve pain in the mouth should follow the recommendations in the product label. Benzocaine products should be stored out of reach of children, and FDA encourages consumers to talk to their health care professional about using benzocaine.


  • There are a number of over-the-counter medications that can be purchased to help alleviate the pain from the ulcer. Most of these have limited studies to support their use and may not be of any benefit:
  1. Glycyrrhiza extract (CankerMelts) which comes from the root of licoriceplant. This has been shown in one study to improve healing and decrease pain of canker sores.
  2. Vitamin B-12 (Avamin Melts): Although recommended by some authors, it has no well performed studies to support its use.
  3. A gel containing polyvinylpyrrolidone, sodium hyaluronate, and Aloe Vera (Canker-X): There is limited evidence supporting the benefit of this compound.
  • Alternative or naturopathic remedies have limited study but are recommended by some providers. Do not use any of these therapies without first consulting with your medical provider. There is almost no evaluation of drug interactions and possible side effects with these naturally occurring compounds. These include the following:
  1. Rhodiola Rosea - 200 mg capsule once a day.
  2. Glycyrrhiza glabra - given as a tea or as a tablet.
  3. Coptis supp, Hydrastis canadensis root - diluted in water and applied to ulcers as needed.
  4. Mahonia aquifolium root - tincture or tea applied topically to ulcers as needed.
  5. Spilanthes acmella flower - tincture or tea applied topically to ulcers as needed.
  6. Alchemilla vulgaris leaf - tincture or tea applied topically to ulcers as needed.
  7. Myrtus communis leaf - Mix power in water and apply to ulcer as needed.


Canker Sore Medical Treatment


Although there is no cure for canker sores, treatment can decrease symptoms, reduce the likelihood that they will return, and prolong periods of remission. Your doctor has a number of treatments available:

  • Silver nitrate can be applied directly to the lesion. A medical provider who is experienced in application should do this; however, the nitrate sticks can be purchased over the Internet. There is a randomized trial demonstrating the efficacy of this treatment. There is almost immediate relief of pain and the lesion heals over the next three to five days. Many patients do not like the burnt taste that they get in their mouth immediately after the procedure but love the total relief of pain within a few hours.
  • Debacterol is a combination of sulfonated phenolic compounds and sulfuric acid that works in a very similar manner to the silver nitrate. It chemically abrades/burns the ulcer. This causes almost immediate relief of the pain and causes the lesion to heal over the next three to five days. It is only available by prescription, but it can be applied by either a dentist or physician. It only has to be applied once.
  • Prescription medications: If over-the-counter medications do not help, your doctor may prescribe one of a number of medications:
  1. Triamcinolone Acetonide Dental Paste USP (Kenalog in Orabase): This can be applied up to three times a day, preferably after meals or at bedtime.
  2. Amlexanox (Aphthasol): This can be applied up to four times a day, after each meal and at bedtime. There is little evidence that the medication actually decreases pain or speeds healing.
  3. Tetracycline suspensions (Achromycin, Nor-tet, Panmycin, Sumycin, Tetracap) used as a mouthwash can relieve pain and accelerate healing; however, their use does not prevent recurrence. Also, use for more than five days may cause problems with reactions and yeast infections in the mouth.
  4. Viscous lidocaine: This is a 2% gel that is applied to the affected area up to four times a day. In order to avoid toxicity, patients should avoid swallowing the medication and should not use the medication more than four times a day.
  5. Sucralfate slurry (Carafate, a prescription medication used to treat peptic ulcers): This treatment is not recommended by many experts and there are limited studies supporting its use. You mix one tablet in 5-10 milliliters (1-2 teaspoons) of water. The slurry is swished around the mouth and spit out four times a day.
  6. The doctor may prescribe folic acid, iron, or vitamin B12 supplements if you are deficient in these. In such cases, you may require several months of therapy to improve. No benefit has been shown, however, from taking these vitamins if you are not deficient.
  7. Corticosteroids: In extremely severe cases, doctors may consider giving oral doses of corticosteroids, if they believe the benefits of treatment exceed the risks of oral steroids. Risks of steroid therapy include weight gain, weakening of the immune system, brittle bones, increase in gastric acidity leading to ulcers, and others.
  8. Thalidomide (Thalomid): In extremely severe cases, doctors may consider using thalidomide. Unfortunately, its severe adverse effects limit its use, and it is only FDA approved for treatment of major aphthous ulcers in HIV-positive patients.
  9. Other potential medications. A long list of medications has been tried and may be used to treat aphthous ulcers in carefully selected patients. Each of these has significant potential adverse effects, and many are quite expensive. These include colchicine, pentoxifylline (Trental), Interferon,Cimetidine (Tagamet), clofazimine (Lamprene), anti-TNF-α agents,infliximab (Remicade), etanercept (Enbrel), levamisole (Ergamisol), and dapsone.
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