I don't think it's been fully explored. What I remember is that he pushed Bullseye to become angrier and jealous at Daken (before the FF crash the party in Darkverine #75), a security guard to sleep with him (#76?) and some clerk to access restricted data files (can't remember the issue). You'd have to draw your own conclusions from that, but it's most likely a conscious choice to release pheromones, he isn't just making an entire hallway moist just by walking by (he probably would, though :D). I don't know but I would think Spider-Woman would be the same in that she can choose when to pheromone up. But if anyone wants to correct me - feel free to.