I suffer from psoriasis. It's not chronic...well, not as bad as it used to be. I've just got a few patches on my legs now.
Unfortunately, I also have it in my hair! My head itches!
So I came up with this method.
Get some Johnson's Baby Oil; the one with Aloe Vera in is best. Add to some warm water. Dunk head. Towel dry. Tie your hair up out the way for at least four hours - overnight if you can manage it. Wash it well and use lots of conditioner. Leave it to dry naturally if you can.
Your hair will feel absolutely gorgeous!