Cold sores are symptoms of a virus and can be awfully painful. As with any virus, these sores run their course in about 7 to 10 days. If these sores appear on or about your lips, keep them moist with some petroleum jelly or some type of soothing ointment for cold sores. Your dentist will be able to help with a safe prescription drug especially for these sores that can lessen the frequency of recurrence and severity. If the sores aren't gone within 7 to 10 days, or worsen, call your dentist!