I would just like to make a suggestion for those who suffer from psoriasis.
Have any of those who suffer from the condition every heard of Kefir? Kefir is a milk drink not unlike buttermilk that is fermented using Kefir grains it has a high ratio of bio cultures, I have know people who have used it and have had excellent results.
You can obtain Kefir on eBay from numerous sellers and it's not expensive. I suggest you use the grains and ferment it yourself it is very easy and low cost.
The prepared ready to buy ( in the supermarket) Kefir is not as potent as the home made version.
I hope it helps someone, please let me know if you try it I would love to know how effective it is and hopefully others can try it.