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Canker Sore

February 27, 2014

Canker Sore

A canker sore is a little ulcer in the protective lining of your mouth. Unlike cold sores, which are caused by the herpes virus, canker sores are not the result of viral or bacterial infections and are not contagious.


Canker sores are caused by:
  • Injuries to the mouth, as seen frequently by contact sports players. Accidentally biting the inside of the cheek or lip may also result in a canker sore
  • Temperature - hot food or drink may cause a canker sore in the area of the mouth that was essentially burnt by the offending substance
  • Spicy and/or acidic foods often produce a canker sore as a response to the irritation these spices and acids create in the mouth
  • The use of chewing (smokeless) tobacco will often cause a canker sore to develop in the area of the mouth where the tobacco is held, due to the irritating chemicals found in the addictive product
  • Poor-fitting, complete or partial dentures may cause canker sores in the area of the mouth where the denture may rubbing on the tissue. The development of a canker sore is often one of the first signs that indicate the need for a denture reline or adjustment by your dentist


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
Pain often 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.


You can treat your canker sore with various home remedies, such as:
  • Salt or baking soda rinse - Mix a few pinches of salt in a glass of warm water. Swish around inside your mouth and spit out, repeating two or three times a day.
  • 3% hydrogen peroxide solution - Mix equal parts water and hydrogen peroxide (3%) and apply to sore with Q-tip. Take care not to swallow any of the hydrogen peroxide if possible. Hydrogen peroxide is an antiseptic that will reduce the amount of bacteria in your mouth and help the canker sore heal.
  • Milk of magnesia - Dab it on active spots a few times a day. The antacid effect of milk of magnesia neutralizes the acidic environment, changing the pH, and making it less supportive of the bacteria in the mouth that aggravate the canker sore.
  • Try to minimize the discomfort of canker sores by avoiding acidic and spicy foods as well as abrasive foods such as nuts, all of which can be irritating.

  • Switch to a toothpaste that does not contain sodium lauryl sulfate (SLS), a foaming agent that may contribute to recurrences.

Do you need to see a doctor?

If you feel very uncomfortable, a doctor will typically prescribe a topical steroid to quell the inflammatory response. Generally, if a lesion lingers more than two weeks, get it checked.