I had heard nightshades were responsible for some cases of arthritis, i didn't really connect it to non-arthritic psoriasis.
I will pass this onto my son. He has it really bad. My husband used to have Psoriasis really bad on one hand and also on his ear and scalp. He went on a diet to lose weight. He really overdoes the caloric restriction when he diets. He was eating between 6 and 8 hundred calories a day and he is 6 ft. Another change is he added vegetables, usually one of those brocolli/carrot coleslaw types in the evening and a lot of veggies at Crazy Bowls and wraps or on a 6 inch low fat subway sandwich for lunch.
Doesn't sound like a magical diet does it? But, his Psoriasis completely disappeared. And on his hand it was so bad it looked disfigured. It was gone for years. Some is coming back now, he has been eating an SAD diet for quite a long time again.
Anyway, I hope this helps my son, I think it is something he could manage. His father's strict diet would be too difficult for him, he says.