Also try to prevent them from being in your yard...I know that's not entirely in your control, but remember that even a small amount of standing water becomes a breeding ground for mosquitos, so look around for anything that might collect water and get rid of it (like a bird bath, empty flower pot, poorly draining area, etc.) My sister's boxer is also allergic - he swells up a lot when anything bites him. She always make sure she has benedryl around so she can give him that if he's reacting to something. You should probably do the same thing.