I do gluten and dairy free. I have been doing this for my Fibromyalgia for several years, so hoping it will also help with psoriasis. I am also caffeine free and try to be as sugar free as possible, therefore limiting the amount of fruit I eat as well. I use lemon to rub on my rash with great success and take apple cider vinegar every day.
I went gluten free for more than a year last year with no change to psoriasis and horrible digestive issues due to eating too many nuts. Now I avoid all dairy which I think is truly not good for my skin and I eat unprocessed, mostly organic food, lots of salads, wild caught fish, no white sugar. In the summer I grow a lot of my food and get lots of sun. I take ginger and turmeric for inflammation, vitamin D3, Cod liver oil, to name a few. My one treat is a glass of red wine, almost every night. I went alcohol free for many months last year with no affect to my psoriasis and felt more stressed, so it stays!