Recurrent canker sores afflict about 20 percent of the general
population. The medical term for the sores is
. Canker sores are usually found on the movable parts
of the mouth such as the tongue or the inside linings of the lips
and cheeks. 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. Canker sores range in size from an eighth
of an inch wide in mild cases to more than an inch wide in severe
cases. Severe canker sores may leave scars.
Fever is rare, and the sores are rarely associated with other
diseases. Usually a person will have only one or a few canker sores
at a time. 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
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
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 B
12, 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 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. Female sex hormones
apparently play a role in causing canker sores. Many women have
bouts of the sores only during certain phases of their menstrual
cycles. Most women experience improvement or remission of their
canker sores during pregnancy. Researchers have used
successfully in clinical studies to treat some women.
Both emotional stress and injury to the mouth can trigger outbreaks
of canker sores, but these factors probably do not cause the
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.
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
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. Mouthrinses containing the antibiotic tetracycline
may reduce the unpleasant symptoms of canker sores and speed
healing by preventing bacterial infections in the sores. Clinical
studies at the National Institute of Dental Research have shown
that rinsing the mouth with tetracycline several times a day
usually relieves pain in 24 hours and allows complete healing in 5
to 7 days. The U.S. Food and Drug Administration warns, however,
that tetracycline given to pregnant women and young children can
permanently stain youngsters' teeth. Both steroid and tetracycline
treatments require a prescription and care of a dentist or
physician. Patients with severe recurrent canker sores may need to
take steroid or other immuno-suppressant drugs orally. These potent
drugs can cause many undesirable side effects, and should be used
only under the close supervision of a dentist or physician.
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. Canker
sores are not contagious, so patients do not have a worry about
spreading them to other people.
Researchers are trying to identify the malfunctions in patients'
immune systems that make them susceptible to recurrent bouts of
canker sores. By analyzing the blood of people with and without
canker sores, scientists have found several differences in immune
function between the two groups. Whether these differences cause
canker sores is not yet known. Researchers also are developing and
testing new drugs designed to treat canker sores. Most of these
drugs alter the patients' immune function. Although some of the
drugs appear to be effective in treating canker sores in some
patients, the data are still inconclusive. Until these drugs are
proven to be absolutely safe and effective, they will not be
available for general use.
National Institute of Dental
Please be aware that this information is provided to supplement the care
provided by your physician. It is neither intended nor implied to be a
substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER
IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the
advice of your physician or other qualified health provider prior to
starting any new treatment or with any questions you may have regarding a
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