I have a horse that is allergic to flies and has very sensitive skin. The fly spray I use has lots of chemicals and irritates his skin. I'm now using a waterbased natural flyspray, but I have to reapply it often and it doesn't work the greatest. I don't want to spend a fortune of flyspray because i've already had to by a flysheet with hood, leg wraps, fly mask, fly traps, special shampoo, and other things for my horse, not even counting the almost $300 in vet bills. Does anyone have a good recipe for effective, cheap, homemade flyspray?