I caught gonnoreah from owo a few years back. Nasty little bacteria that one.
Since then I always have oral with ( bar once where I slipped up ).
Just not worth the worry when your balls start to ache and greeny yellow puss starts oozing out your nob.
Plus, when you think about it, it's pretty gross to think another guy, or two, or three, has had their cock in that girls mouth before you today and maybe filled it with their jizz....