http://psoriasis.about.com/od/holisticapproach/i/diet.htm
There are pharmaceuticals used to treat Psoriasis, but these involve suppressing the immune system to help with the body attacking its own skin. These are still experimental or at least relatively new pharmaceuticals. I don't have Psoriasis myself, so I don't know much about the pharmaceuticals for it. I do see commercials for one that has been promoted, but I hate to say anything about it, since I've never used it. Check at the top of your medhelp page under health information, because there is a link to Psoriasis there. I saw a small section that lists some pharmaceuticals there.