A canker sore is a painful, open sore in the mouth. Canker sores are white or yellow and surrounded by a bright red area. They are not cancerous.

A canker sore is not the same as a fever blister (cold sore).

Aphthous ulcer; Ulcer - aphthous

Canker sores are a common form of mouth ulcer. They may occur with viral infections. In some cases, the cause cannot be determined.

Canker sores 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 also be triggered by:

• Emotional stress
• Lack of certain vitamins and minerals in the diet (especially iron, folic acid, or vitamin B-12)
• Menstrual periods
• Hormonal changes
• Food allergies

Anyone can develop a canker sore. Women are more likely to get them than men. Canker sores may run in families.

Images

Mouth anatomy

Canker sore

Canker sore (aphthous ulcer)

Review Date: 02/17/2011
Reviewed By: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)