My sympathy Brucie---I've got an identical complaint! I know what caused mine, though. I had been cursing a small irritating boil situated just at the top end of the "crack"-o'-my rear.. My beloved partner got her eye on it [ no----I'm answering NO questions on that score----] and gave a fair sqwawk of dismay 'Your boil's got legs!" It was a deer ttick, it turned out, which had been burrowing its way into my arse for a week in order to lay its eggs. Ha! --Emergency, a doc with a pair of tweezers and a tetanus update. And now, a damnably itchy remnant. Aye---it drives me nuts, too!