I don't know about the wheat thing showing up at 1.5, but that doesn't sound that odd to me. I think a low grade allergy can easily go unnoticed for a while and take a while for symptoms to build. May be a different food thing though. Or not at all! If you do elimination, you probably want to aim for a month or so. Check out the allergy forum too...
And here is a link with pillow and other encasings here:
http://www.natlallergy.com
may not be allergies at all, but in my experience with ds, it was.
good luck!