There's a theory of its affect on your acne. Wouldn't be the cause of it, but it might give it a little boost if you've already suffered from it. When you cum, your hormonal balance and testosterone levels go all over the place, shit like that.
Perhaps the reason I still haven't quite kicked it.
Very interesting because I have also read somewhere(cant remember where) that in some males, heavy weight lifting workouts that increase testosterone production also trigger acne.