Cold sores are an extremely common condition of the mouth. Also known as
fever blisters (and known medically as herpes labialis), cold sores are the result of being infected with a herpes simplex virus.
Despite its two common names (cold sore and fever blister), you do not need a cold or fever to get a cold sore.
(Click Cold Sore Causes to learn more about the different types of herpes simplex viruses and how they can cause cold sores.)
Cold Sores Versus Canker Sores
Many times, cold sores can be confused with another common mouth condition known as canker sores. Both can cause small sores in or around the mouth. Canker sores, however, occur only inside the mouth -- on the tongue and the inside linings of the cheeks, lips, and throat.
Cold sores, on the other hand, usually occur outside the mouth -- on the lips, chin, cheeks, or in the nostrils. When cold sores do occur inside the mouth, it is usually on the gums or the roof of the mouth. Inside the mouth, cold sores are smaller than canker sores, heal more quickly, and often begin as a blister.