I'm no expert, but after having delved into this subject quite often, my best guess is that something might be wrong with your LIVER. The Liver is 1 of the most important Detoxifiyers . It sounds like an overload on it... too much of some toxin either acute or long term build-up .. (like the straw that broke the camels back).
over 50 yrs. ago, I got a blood disease from Bacteria I had picked-up in the Ocean in the Virgin Islands.. It caused INTENSE Itching - especially on palms, arches, back... and all over allergic reaction after a hot shower....long story short- months later I would up w/ Staffoccocal pneumonia.... anyway, just something to ask your doctor about.
Rumi-Tunes3