Canker sores are small shallow ulcers that appear in the mouth
and often make eating and talking uncomfortable. There are two
types of canker sores: - Simple canker sores: These may appear
three or four times a year and last up to a week. They typically
occur in people between 10 and 20 years of age. - Complex canker
sores: These are less common and occur more often in the people
who have previously had them. What causes canker sores? The
exact cause of most canker sores is unknown. Stress or tissue
injury is thought to be the cause of simple canker sores.
Certain foods -- including citrus or acidic fruits and
vegetables (such as lemons, oranges, pineapples, apples, figs,
tomatoes, strawberries) -- can trigger a canker sore or make the
problem worse. Use of nonsteroidal anti-inflammatory drugs, like
Motrin, is another common cause. Sometimes a sharp tooth surface
or dental appliance, such as braces or ill-fitting dentures,
might also trigger the sores. Some cases of complex canker sores
are caused by an under