^ There are human fly repellants made with some of the same repellants as horse ones, so you could check some of those out if you ever got curious.
Apple Cider Vinegar is a good way of keeping pests at bay too...you can put some in their feed daily (which is what I do to my mare, although she's been off of it for a little while, cause hubby ran over my new gallon of it, and I haven't gotten a new one). Or you can put it in some of their drinking water, but you have to make sure to change that daily, and that can get annoying, which is why I feed it. My girl loves it!
"The ideal horseman has the courage of a lion, the patience of a saint, and the hands of a woman..."