Many people develop cold sores or so-called “fever blisters” on their lips or in their mouth. These lesions are caused by the herpes virus, and they can easily be passed from one person to another, or even to other parts of the body. Various conditions, such as drying the lips, sunburn, a high fever, or stress can cause cold sores to erupt. The causative agent for these lesions stays in the body once you have had it. Fortunately, they heal in about one week.
These lesions can be spread easily. Be careful! There is no known cure for cold sores.