health

Canker sores are small patches of raw skin on the tissues that line the
cheeks and the inside of the lips. They may also occur at the base of the
gums or below the tongue on the floor of the mouth. They may appear
as single ulcers or in clusters. Most are about three-eighths of an inch
(1 centimeter) wide, but some are larger.
Doctors classify canker sores into three groups: minor sores, which are
smaller than half an inch (1.3 centimeters) and heal by themselves in seven
to ten days; major sores, which are larger than half an inch (1.3 centimeters),
are usually deeper than minor sores, may take as long as a month
to heal, and may leave scars; and herpetiform sores, which are small, form
clusters that look like the fever blisters caused by herpes viruses, and
heal in about a week. About 80–85 percent of canker sores are minor
sores, 10 percent are major sores, and 5–10 percent are herpetiform.