You go on a holiday to a nice warm beach and when you return home your upper lip feels itchy and it tingles. One day later there is a small sore on the edge of your lip. Is this a sun blister? Most likely you have the manifestation of a herpes infection. Did this infection come from drinking foreign water or from a glass not cleaned properly? Herpetic lesion s are initiated by many factors including direct sunlight . The initial virus was probably residing very quietly in your body since infancy. These lesions which look like little blisters(vesicles) are known as herpes labialis and they will stay on your lip regardless of over- the counter- medications that promise to heal them immediately. Most herpetic lesion will last 7 to 10 days. The medication may reduce the healing period by one day. It should be noted during the vesicle stage, the carrier is considered very contagious. A simple act of kissing will probably spread to another individual.