Canker sores and cold sores are very painful sores found inside or around the mouth. There are many misconceptions about what exactly these things are and where they come from. While canker sores have no exact cause cold sores are caused by the herpes simplex virus. Canker sores are not contagious, but cold sores are highly, and are the same virus that causes genital herpes. Canker sores are believed to be caused by bacteria which get into an open wound, cut, friction or burn in or around the mouth, as well as a vitamin deficiency in B12, folic acid, and iron, as well as hormonal changes associated with menopause and pregnancy, and could even be symptoms of numerous immune deficiency diseases. There is no treatment for canker sores, while cold sores sometimes require ointments and sometimes prescription medications. Cold Sores and Canker sores can go away between two days and two weeks on their own. While these legions do go away without you seeing your doctor or dentist, you should see them if it does not go away in two weeks, begins to get larger, begins to look infected, or interferes with your eating or drinking you should seek medical attention.