Most cold sores are actually Herpes Simplex, which is a virus, and very contagious until it crusts over. They "can" also spread to your tongue and gums. If this is your first outbreak I am sure it is painful. They can last anywhere from 7-10 days. So if you kiss someone they could get Herpes and that is how it is spread. If it gets too painful or more on the surface, call your doctor for some anti viral meds. I dont know how to put this any other way, however if you give oral sex, the man can get Genital Herpes.