I had psoarisis since I was 7, and currently i'm 15. No one knows how I got it but I have had alot of stress in my life, so that could have triggered it.. But anyway, How i treat it is sit out in the sun for a while no more than a hour or 2 every other day. I think this is the best way otherwise, take vitamin E pills every night after dinner because then it works while your sleeping.
I have psoarisis on my legs, knee, stomach, arms, back, and scalp. I just left my face last winter. but it was very humiliating, and lowered my self esteem like 100%.
But this is how i treat it. it's the best way i believe, hope i helped.