Although often considered the same thing, canker sores and cold sores are actually completely unrelated. A canker sore usually appears on the tissues inside your mouth. While these sores have a light-colored base, they also often have a red exterior border. A cold sore (fever blister) usually appears outside of the mouth on or near the lips or nose. Cold sores, a manifestation of the herpes simplex virus, are filled with fluid, are usually painful, and are contagious.

For most people, canker sores will disappear over time. To help remove canker sores, it is best to practice good oral hygiene and maintain a healthy diet. You may also use a special rinse or anesthetic to help remove a canker sore. Cold sores, on the other hand, can be treated with over-the-counter creams or an antiviral medication prescribed by the doctor.