Military uses permethrin treated clothes. I bought some to reapply to my pants, and the ticks on me weren't as bad as my previous trips. I don't typically use insecticides, so it's only a single data point. It'll work on mosquitoes, but I don't think it'll work for deer flies. Long sleeves/pants, and light colors for deer flies. If you have one harassing you, raise a hand over your head. When it lands on that hand, hit it with the other. They gravitate to highest part of your body.