What Are Cold Sores? What Causes Cold Sores?

Cold sores (a cold sore), also known as fever blisters, are small sores, or blister-like lesions on the face or inside the mouth. They usually cause pain, a burning sensation, or itching before they burst and crust over. Most commonly, cold sores appear on the lips, chin, cheeks, inside the nostrils, and less frequently on the gums or the palate (roof of the mouth).

Source: What Are Cold Sores? What Causes Cold Sores?