Edgar Cayce said that both Psoriasis and eczema are caused by the thinning of the walls of the intestine, which allow unproccesed food through. Then the 'poisons' from the food particles attempt to come out in the skin.
His fixes for leaky gut are VERY EASY - just drink slippery elm tea in the morning, and throughout the day if its severe, and american saffron tea in the evening. (american saffron is the cheap stuff, its the italian saffron which is expensive). He also said to get chiro adjustments on t6-9 because these vertebrae put pressure on the small intestine which then continue the thinning.