I had it on TX and treated it with 10% hydrocortisone cream. It improved it but it didn't leave until a month past TX. Has not come back. Interferon can make you "allergic to yourself" in several ways but it should go away after you stop the interferon.
i have had psoriasis really bad since tx started,i think its pretty common,it should go away after you stop tx.
I actually had a very slight skin probs b4 tx too so i think us who are prone to skin probs get it bad on tx.
good luck with tx and i hope your skin probs get a bit better for you.