Aphthous Ulcers, (canker sores)

Canker sores are small and often painful ulcers on the inside of the mouth. They are medically known as aphthous ulcers. About 20% of the population experience canker sores from time to time. The percentage is higher among women, who are more likely than men to experience recurrent sores. Studies have shown that susceptibility to outbreaks may be inherited in some patients. This partially explains why family members often share the condition.


The sores in nose tend to occur on the movable parts of the mouth, such as the tongue or the inside lining of the lips and cheeks. 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. Canker sores range in size from an eighth of an inch wide in mild cases to more than an inch wide in severe cases.

Generally, the sores heal within 2 weeks without scarring. Fever is rare, and the sores are rarely associated with other diseases. Most usually have only one or a few canker sores at a time. And typically a person will experience only one or two episodes a year. Canker sores are not contagious, so patients do not have to worry about spreading them to other people.

What causes a canker sore?

The cause of canker sores is not well understood. More than one cause is likely, even for individual patients. An allergy to a type of bacterium commonly found in the mouth may trigger them in some. The sores may also be an allergic reaction to certain foods. In addition, there is research which suggests 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.

Other causes of canker sores are injury to the gums from brushing and 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 Bechet’s syndrome. Smoking and dentures can also contribute to the problem.

Female sex hormones also may 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.


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

The treatment depends on the cause. Patients with food allergies can reduce the frequency of canker sores by avoiding those foods. If the cause is another illness, such as lupus, treating the underlying illness often results in healing the ulcers. In some cases, something as simple as changing toothpastes may get rid of recurrent canker sores. A natural toothpaste or a toothpaste that doesn’t contain additives (especially sodium lauryl sulfate) is sometimes helpful.

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.

Most cases of canker sores do not reflect an underlying illness. However, if you are having canker sores frequently, be sure to consult your health care professional.