A canker sore is a painful, open sore in the mouth, which is white or yellow and surrounded by a bright red area. A canker sore is benign (not cancer).

See also: Herpes

Canker sores are a common form of mouth ulcer. They occur in women more often than men. They may occur at any age, but usually first appear between the ages of 10 and 40.

Canker sores usually appear on the inner surface of the cheeks and lips, tongue, soft palate, and the base of the gums.

Canker sores can run in families. They may also be linked to problems with the body's immune (defense) system. The sores may occur after a mouth injury due to dental work, aggressive tooth cleaning, or biting the tongue or cheek.

Canker sores can be triggered by emotional stress, dietary deficiencies (especially iron, folic acid, or Vitamin B-12), menstrual periods, hormonal changes, food allergies, and similar situations. They occur most commonly with viral infections. In some cases, the cause can not be identified.

The first symptom is usually a tingling or burning sensation that you feel before other symptoms develop.

The following symptoms may then occur:

• Painful, red spot or bump that develops into an open ulcer
  • Center is colored white or yellow
  • Usually small (under 1 cm) but occasionally larger
  • Single bump or group of bumps (crops)
• Sore may turn gray just before starting to heal

• Fever
• General discomfort or uneasiness (malaise)
• Swollen lymph nodes

Pain decreases in 7 to 10 days, with complete healing in 1 to 3 weeks. Particularly large ulcers (greater than 1 cm in diameter) often take longer to heal (2 to 4 weeks). Occasionally, a severe occurrence may be accompanied by nonspecific symptoms of illness, such as fever. Canker sores often return.

Your health care provider can often make the diagnosis by looking at the sore. If canker sores persist or continue to return, tests should be done to rule out other causes, such as erythema multiforme, drug allergies, herpes infection, bullous lichen planus, and other disorders.

In rare cases, a type of cancer may first appear as a mouth ulcer that does not heal. See: Squamous cell carcinoma.

A skin lesion biopsy may be used to distinguish a canker sore from other causes of mouth ulcers.