I can relate to Insane Itch. Mine is related to vasculitis. The kind of vasculitis I have is Th2 related. Th2 is related to the humeral immunity. Humoral immunity refers to antibody production and the accessory processes that accompany it, including: Th2 activation and cytokine production. Histamine is involved with this. controlling histamine usually controls itch.
I take a powerful prescription antihistamine orally to control vasculitis and itch. I also use benadryl cream topically. I find the benadryl cream very effective. (as a side note benadryl orally is ineffective for me.)