Thanks to you both for your replies, Robin and CC. Not sure how I missed Mug's original itchy thread -- maybe I wasn't itching that day!
The exercise thing is fascinating, and it makes sense. The foods I'm eating aren't all that different than what I usually eat, just a whole lot less of them and with healthful substitutions where appropriate. I'm drinking lots more water, so skin is probably better hydrated than usual.
I'll definitely start moisturizing more regularly and will try the fish oil as well, but if itching is one of my punishments for slothful living, then I'll just have to get through it... I refuse to be deterred by something so dumb!!
Thanks again for your help.