Are cold sores the same thing as canker sores?
No. Although these sores are often confused for each other, they are not the same. Cold sores, also called fever blisters or herpes simplex type 1, are groups of painful, fluid-filled blisters. Cold sores are caused by a virus and are extremely contagious. Canker sores are not caused by an infection and so are not contagious. Also, cold sores typically appear outside the mouth — usually, under the nose, around the lips or under the chin, while canker sores occur inside the mouth.