Well, someone had mentioned that the cooling process moves through the blood in your wrists? That may be true, but look at it this way. You could use some sort of hat/cap system that could cool you down.
Now dont say this wouldnt work, because think of it like this. When your out walking or running, or just doing somthing strenuous enough to get you a sweat, and you dump water on your head, doesnt that cool your whole body down? It does for me, I might be wrong but, I think you should try it, or maybe I will try and come up with somthing. Just some ideas.?
Good luck.