Im no doctor but from what I learned in health class and dr drew. If its something like herpes it can be spread orally. There are some diseases that you can spread orally and others just need to touch the area the outbreak is in

How about hiv?

Yes, you most certainly can get hiv from oral sex. There is an exchange of fluids; although she is far more likely to get hiv from you, and less likely she can spread it to you; because saliva just doesn't have as many hiv cells in it as compared to semen, vaginal fluids, blood, and breast milk. That's why it's almost impossible to get hiv by sharing cups, toothbrushes, or kissing. But semen? Semen definately carries the virus. So the chances of a man getting hiv from a girl who is giving him head is very low, i'd say. Still, if you are worried it's far better to get a test... Although you do have to wait a while before anything will show up on a test.