I have spent 6 years in study of just one Ayurvedic product. Neem. nim, margosa seems to have quite dramatic effect on ALL forms of Psoriasis. Discomfort is relieved with almost immediate effect due to the analgesic qualities. My research was conducted for a UK company and they have been kind enough to post on their site. One thing I must stress is that not all Neem oil is the same and the most beneficial is Indian or Korean produced product. The active molecule is azadirachtin and it seems the US, and Austrailian trees only produce approx one third the amount 500ppm compared to 1500ppm of Indian Neem.
Research at http://www.neemgenie.co.uk/condition.html