Cold sores (also called “fever blisters”) appear as clusters of red, raised blisters outside the mouth, typically around the lips, although they can develop under the nose or around the chin. The blisters are filled with fluid and can break open, allowing the fluid to lead out. They then can scab over until they heal. Cold sores are caused by the herpes simplex virus and are highly contagious. The initial infection with the herpes virus can be accompanied by cold or flu-like symptoms and can cause painful oral lesions. There is no cure for the herpes virus; once you are infected, the virus stays in the body and causes occasional flare-ups associated with the cold sores. Cold sore blisters usually heal by themselves in about one week. Over-the-counter topical anesthetics can provide some pain relief. Zovirex is a compound we dispense to reduce the healing time for these sores.