It just HURTS!

Now...I have a problem I've been dealing with for several months and its just not getting any better. I have a rash of some sort on my hand that itches, oozes, hurts like hell, peels, gets raw and is swollen. I've been to the dermatologist who says it is a form of psoriasis, but also an allergic reaction to something, but I haven't got a clue to what it is. I've never had this before and I can't imagine that all of a sudden something that I've been doing/using all my life is now creating this mess on my hand.

I thought maybe it was from a certain yarn. It is the finger I wrap my yarn around when I am knitting. The derm said that yarns with blue dye seem to cause problems...something about the indigo in it. I am working on the purple wrap for my sister, but I can't tell for sure if it is from that yarn since this will clear up and then come right back. I haven't worked on the wrap in two weeks so who knows. People have said it looks like poison ivy, but I can assure you, it is not.

I've tried Benedryl cream for the itching, which helps but burns. I have a script from the doc but that seems hit or miss lately. This picture is from today. It's looked 50 times worse - but its starting on that downswing of getting bad again. Anyone ever see anything like this??