Screw the Calomine.

Screw the cortisone creme.

Get thee to a doctor and have a shot of hydrocortisone injected in your nether parts.

When I lived on the hill in Sausalito, the cats or the Blessed Ex would manage to get the stuff on me. Cats usually seemed to produce mild symptoms. The Blessed Ex.... I say "DON'T *EVEN* TOUCH THAT!!!!" as we pass a bush. "What, this?" she says, touching it. Fortunately, she was a doctor (that's the D in EPBKDGFH). So she's all apologetic and procures some hydrocortisone, though I think she took a bit too much pleasure in administering it. That's about the only thing that deals with the stuff for me, and if you were actually hacking away at it, I'd strongly recommend same. After the first day, symptoms are drastically reduced, by the end of a week, it's pretty much all gone. Without, the stuff runs for weeks with me.

Past three years, away from her, and well away from any visible quantities of PO, I've been clear.