No kidding. I found out the hard way. I didn't know what was causing the itchy blisters, (thought it might be some new drilling mud additive) so I dug one open under the microscope and found a bug. I drew a picture of it, showed it to the doctor (who treated me like a leper from then on) and was informed (after inquiring) what the critters were.
They aren't hard to get rid of, but who wants them!