Is it possible to have herpes on the breasts from "breast sex" or semen on them?
Thanks for your question, it's an interesting one. Though I'm not a doctor, I do have herpes and think I can answer you.
Though skin herpes does exist, it is a different strain of herpes than the genital or oral kinds. Herpes can live in various bodily fluids, like semen, but needs to come in contact with another mucous membrane, like the genitals or mouth, in order to be transmitted to someone else. So it is not possible to get herpes on the breasts through semen, unless the woman has an open cut or sore on her breasts, or if the semen touches her mouth of genitals. That said, I would advise against having "breast sex", or any other sexual relations, when the infected person is having an outbreak.
For more information I recommend you check out the Transmission and Causes and Risk Factors pages of this site.