I have to locate utilities, so I'm walking in waist high weeds all summer. Dose down with Deep woods off, as was mentioned. If I do get bit, I use a method I just learned of this year. Turn the hot water on, and let it run until the steam is rolling. Stick a spoon under the water for a few seconds then press the spoon down hard on the bite and don't let up. Feels like sticking a needle right through the middle of it, but it will kill the itch. Hurts like he77, but it's worth it.
The best preventative I ever heard of was from another locater who wears shorts all summer. I asked him how he keeps from getting ate up, he said "easy, just smoke a lot of pot and eat a bunch of jalapenos!" I've only tried half of his recipe so far, won't say which half but I will say I like hot spicy food.
I'll also say, be glad you have chigger bites and not turkey mite bites. Those things are chigger bites x100.