Canker Sores
(Aphthous Ulcers)

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Medical Author:

Siamak T. Nabili, MD, MPH

Siamak T. Nabili, MD, MPH

Dr. Nabili received his undergraduate degree from the University of California, San Diego (UCSD), majoring in chemistry and biochemistry. He then completed his graduate degree at the University of California, Los Angeles (UCLA). His graduate training included a specialized fellowship in public health where his research focused on environmental health and health-care delivery and management.

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Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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• Canker sores are small ulcer craters in the lining of the mouth.
  
  
• The sores are usually found on the movable parts of the mouth.
  
  
• The ulcers can be caused by a number of conditions.
  
  
• The treatment of canker sores depends on the cause.

Canker sores are small ulcer craters in the lining of the mouth that are frequently painful and sensitive. Canker sores are very common. About 20% of the population (one out of five people) have canker sores at any one time. Canker sores are also medically known as aphthous ulcers or aphthous stomatitis.

Women are slightly more likely than men to have recurrent canker sores. It can occur at any age, but it is more commonly seen in teenagers. Genetic studies show that susceptibility to recurrent outbreaks of the sores is inherited in some patients. This partially explains why family members often share the condition.

Canker sores are generally classified into three groups based on size.

1. Minor sores have a diameter of 1millimeter (mm) to 10mm. They are the most common (80% of all canker sores) and usually last about 7-10 days.
   
   
2. Major sores (10% of all canker sores) have a diameter of greater than 10mm and they may take anywhere between 10-30 days to heal. They may leave a scar after they heal.
   
   
3. Herpetiform ulcers (10% of all canker sores) are formed by a cluster of multiple small individual sores (less than 3mm). They also usually heal within 7-10 days.