I had a long and weird experience with psoriasis in the mid-90s with psoriasis. I always thought it was an allergic reaction to the stupid McDonald's hat that I had to wear for nearly the entire 8yrs I worked for McDonald's.

Then I thought that it was from all the sweating I did in the heat of the McD's that I worked at.

I finally decided it was my shampoo and after using T-Gel for a long time, I found a decent shampoo and never really had a problem with the psoriasis since then. (altho, I think I have a little patch of it on my neck near the pulse point for the past few weeks)