I took Fumaderm and the white cell count went down but the p had started to clear.
Then the cell count went up and the p came back so we had another go. It worked 'just' as the white cell count started to get perilously low again - The p had all but cleared surprising my Dermatologist as I'd extensively thought I'd be 'clever' and do some looking around myself for some sort of relief. In fact my previous D suggested I come into hospital for a week which I refused convinced there had to be some sort of relief.
Sadly 18 months later and the p is coming back again so off we go down the Fumaderm route - Funny enough I must be very lucky because from memory it did not take that long to work effectively previously.
Years ago I had Acetretin which failed and never went down the MX route because I like the occasional drink. I had PUVA treatment which ahem, failed when I was overexposed and let me assure anyone that literally 24/7 itching was not pleasant which lasted for around a week. I've also used various Coal Tar products and Dovobet (and Dovonex when it used to be available) which did nothing to relieve the conditions.

What I would say is the personally I've always been so impressed by the hospital Consultant's and nurses who have all been so helpful and considerate to me over the last 25 years.
Michael