Yup... chigger/redbug expert here too. I live in the woods in Mississippi! They burrow into the skin and those tight undie and bra bands give them a head start on getting down in your skin. Once you kill them (with your favorite poison-- alcohol, bleach, whatever...) then you will still itch for about a week while their little dead bodies disintegrate down in your pores. It's much better to wear bug spray when you go outside (YUCK!) than to deal with chiggers for a week after if you don't.
They aren't bad here this year, for some reason. Usually you can't go outside without picking up some. And FORGET sitting on the ground for any reason.
The joys of summertime....