Psoriasis is not a skin disease. It is an auto-immune problem. So treatment has to be aimed at the source, which, I believe, is the digestive system.
Your diet needs to be pretty much the same as for candidiasis. No sugar, no white flour including all its products, no beef, pork or veal, etc. Also avoid all nightshade family of veggies,
which includes tomatoes and all foods containing tomatoes, blueberry, white potatoes, eggplants, etc. You can eat sweet potatoes, a lot of veggies, fish, chicken and limited amount of lamb.
No fried foods. Boiled, steamed, saute'd. Also it is important to keep your digestive system cleaned so mild laxatives, plus enemas or colonics are necessary.
I am on this cure for 3 weeks now and my psoriasis has improved in the last two-three days quite noticeably.