Probably mites as Linda said. I had moths in an old carpet of mine once - just under the heavy furniture that isn't moved regularly for cleaning. I had no idea until I did move everything and vacuumed - all the carpet fibres disappeared into the machine leaving me with the hessian backing! I couldn't believe my eyes - and when I found the culprits had to take it all up and burn it. Have you tried an anti histamine to see if it stops your itching? Hope you get some sleep tonight, Ed.I found a date of 1986 under one section of carpet. I'm wondering if the fibers have broken down into something that is an irritant.
I had no idea it was that old. It still looked pretty good.