I use Repel brand Permanone. It is an insecticide not a repellent and it works fantastic. I used to get hundreds of chiggar bites and now I seldom get more than just a couple a year. It works great on ticks too.

You spray it on your boots and clothes, not your skin. It doesn’t repel them, it just kills them! Best of all it really works and lasts for a couple weeks too. You can get it in the sporting goods dept. at Wal-Mart.