I have read that Spirulina tablets -- taken internally, of course -- can help with such problems.
I have started to take external oil treatments. I found online a company that sells various oil treatments in a small bottle. You just rub that on your skin condition and it is suppose to heal it up. They sell oils for all kinds of skin conditions, and there is one made especially for psorisis. I just started on this bottle. I'll keep you posted with results. Just go online and search for treatments with oils and perhaps that company will come up.