I wish I could help. I have not been diagnosed with psoriasis or psoriatic arthritis, although I do think I would have it if I ate dairy. Dairy gives me terrible itching, a rash on my scalp and back, and terrible joint pain. I can’t even have butter.
There are other people on this forum with psoriasis who may be able to weigh in.
I am currently reading, “The Paleo Approach: Reverse Autoimmune Disease and Heal Your Body” by Sarah Ballantine, PhD. I am still in the beginning pages about how the immune system works so I can’t comment on it. I started reading it because a few people on this forum mentioned using the paleo autoimmune protocol (AIP) and that it really did help their autoimmune diseases.
I wish I could have more information for you. My brother who I mentioned earlier in the thread. Does not eat a keto diet, so I don’t know if that would help him or not. I wish he would give it a serious try. He avoids all dairy like the plague.
I did buy him a book several months ago about healing psoriasis naturally. Once I look up the name I will add it to this post. He has found it quite interesting. Has he implemented any of the book’s suggestions? I have no idea. 
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