I too suffer with psoriasis, I was told about Oregon Grape Root cream and within 3 weeks of using it the worst of the psoriasis had gone and I have only a few small patches now. I would highly recommend it. It is available from
www.skinshop.co.uk and is made with only natural ingredients. I only ever use this now.
If you are advised to try 'Epaderm' cream, don't bother, it doesn't work too well and costs £13 for a bottle although I got mine on prescription (£7.40) but when I checked the ingredients it is the same as the aqueous cream available from Home & Bargain for £1 :-/ !!