Apr 07, 2015 - 10:44 AM
I can't tell you what the problem is if you can't find an insect. 99% of all insects are visible with the human eye.
There is a chance, that it could be chiggers. This is the immature stage of a mite. They are found outdoors in fields. Seldom indoors.
Here is a quick link to some helpful information - http://www.epestsupply.com/bugs-insec...