What Bert said. Chiggers will leave individual red bumps, usually where you have natural skin creases or in places where you clothing had close contact with the skin -- under your socks, around elastic wasitbands, back of the knees, etc. They like to hang out in tall grasses and weeds on hot summer days. Spray yourself from the knees down with Deep Woods OFF, put on your socks, spray the socks, then put on your hiking boots, then spray the boots. If you're wearing long pants, spray the bottoms of the pants legs. That helps somewhat, though a lot of folks don't like to be bathed in petrochemical toxins like that. I just tend to save those bushwhacky caches until winter time when the chiggers aren't active.
We don't have much (if any) poison sumac around here, but there's lots of poison ivy and some poison oak. Learn to ID it and stay away from it. It tends to leave bigger rashy blotches instead of the individual bumps that chiggers do. You can buy Ivy Block at the drugstore and apply it to exposed skin before venturing out just in case you inadvertently come in contact with it. I keep Tech-nu Poison Ivy wash in the truck along with a roll of paper towels to wipe down with whenever I know I've accidentally gotten into the stuff. P.I. can be just as poisonous in the winter time, but harder to identify since the leaves have fallen off. Look for "fuzzy" vines growing up tree trunks and DON'T TOUCH THEM!
Heres a good reference on poison ivy: http://www.bami.us/PoisonIvy.html
Here's a picture of the vine, sans leaves:
Edited by HoustonControl, 08 July 2013 - 09:29 AM.