It could be a blood disorder called Polycythemia Rubra. See a blood doctor or an Oncologist - they know about such things.
A related discussion,
crawling sensation was started.
For me, it was a side effect of a medication. i stopped it, and now i am fine.
@ rrobby37 he is on to something there.Do that one!
It could be caused by food allergies. Or perhaps fleas.