Want to know more about canker sores and how to treat them?

We asked the National Institute of Dental and Craniofacial Research for some straightforward answers.

We know: All About Canker Sores

What are canker sores?

Canker sores are small sores that occur inside the mouth on the tongue and the inside linings of the cheeks, lips and throat. They begin as small oval or round reddish swellings, which usually burst within a day. The ruptured sores are covered by a thin white or yellow membrane and edged by a red halo. Generally, they heal within 2 weeks.

(Cold sores or fever blisters can occasionally also occur inside the mouth, but they are smaller than canker sores, heal more quickly and often begin as a blister. See our article, All About Cold Sores for more information.)

What causes 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.

Both emotional stress and injury to the mouth can trigger outbreaks of canker sores, but these factors probably do not cause the disorder.

Who gets canker sores?

Recurrent canker sores afflict about 20 percent of the general population. Most people have their first bout with canker sores between the ages of 10 and 20. Children as young as 2, however, may 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.

Women are more likely than men to have recurrent canker sores. Genetic studies show that susceptibility to recurrent outbreaks of the sores is inherited in some patients. This partially explains why the disorder is often shared by family members.

Are cankers sores contagious?

No.

What are the treatments for canker sores?

Most doctors recommend that patients who have frequent bouts of canker sores undergo blood and allergy tests to determine if their sores are caused by a nutritional deficiency, an allergy or some other preventable cause. Vitamins and other nutritional supplements often prevent recurrences or reduce the severity of canker sores in patients with a nutritional deficiency. Patients with food allergies can reduce the frequency of canker sores by avoiding those foods.

There are several treatments for reducing the pain and duration of canker sores for patients whose outbreaks cannot be prevented. These include numbing ointments such as benzocaine, which are available in drug stores without a prescription. Anti-inflammatory steroid mouthrinses or gels can be prescribed for patients with severe sores.

What can the patient do?

If you have canker sores, avoid abrasive foods such as potato chips that can stick in the cheek or gum and aggravate the sores. Take care when brushing your teeth not to stab the gums or cheek with a toothbrush bristle. Avoid acidic and spicy foods.