A canker sore is an open and painful mouth ulcer appearing whitish, often with a red halo. Its cause is unknown, but they are not contagious.


  1. Wikipedia, the free encyclopedia (www.wikipedia.org).
  2. Medical dictionary by Farlex (www.thefreedictionary.com).

The information above should be used as a reference only. Any medical decision should not be taken before consulting a health care professional.

The masculine gender may have been more used in the article, but without prejudice, to make reading easier.

Category dental problems