I don't think it's a cologne, aftershave or parfume that switches on arousal, though I do know the application of an excess or a stale, oxidized scent is a huge turn off....But rather the pheromones that a man exudes through his pores.
If behavior, looks, humor, personality "click" the down fall can be he just doesn't smell right to her nose.
It's the "chemistry" factor of the equation that is given a certain "mysticism" and taps into the more primitive hindbrain functions.
Simply put, never fuck someone who smells bad.