My son, daughter, husband and I all have psoriasis on our scalps. Even when there isn't an actual outbreak, we have incredibly dry scalps.
I have tried tea tree oil, moisturizers in the shampoo, no-poo, but none of these things has offered any kind of longish term solution.
Certified Crazy™ Wife to my Spiderman husband (Aug '01)
Super proud Momma to DD (Jan'00), DD (Apr '02) and DS (Jun '04)
Always loving and missing our Baby James born sleeping at 19 weeks (July '03).
As a hairdresesr, I have a few thoughts!
How often are you shampooing? My first thought would be the longer you can go between the better, so the natural oils can build up. (When I say not shampooing, I mean don't even get it wet on your days off. They do make some pretty cute shower caps )
Another gentle option would be using coconut oil on the scalp as an intense moisturizer. Try working some into your scalp at night, sleep on it (Throw an old pillow case on your pillow first) and then use a soft bristle brush to gently massage your scalp before washing the next morning. I would try that once or twice a week and see if you notice any changes.
Hope this helps!