The Facts
Canker sores are small sores that appear on the inside of the mouth, especially
the cheeks and lips. They're also called aphthous ulcers. Rarely,
they may develop on the gums or on the roof of the mouth. Small canker sores
disappear within 10 days and don't scar. Large ones are less common, take weeks
to heal, and can leave scars. Canker sores aren't contagious.
At any given time, 20% of Canadians will have a canker sore. They're most common
in women and in people aged 10 to 40 years. Many people get them regularly,
at least once a year. In the most severe cases, people get one after another.
Causes
Doctors don't know exactly what causes canker sores. They may be hereditary,
but doctors have not figured out exactly how people inherit the tendency to
get them. Researchers think they may be an overreaction to the Streptococcus
bacteria, because the bacteria are often found in the canker sore. People with
canker sores often have small injuries from dental injections and toothbrushes
in the lining of the mouth. Allergies, such as hay fever, are also associated
with an increased risk for canker sores.
Canker sores often occur near the time of a menstrual period. They may also
be brought on by stress - for example, many students get them during exams.
Other possible causes include lack of cyanocobalamin (vitamin B12), folic
acid, or iron. Certain foods may be triggers for canker sores or act as nutrients
for the Streptococcus bacteria.