For some reason, the risk of UV doesn't seem as high in psoriasis patients as patients without psoriasis. I'd use UV versus a drug like methotrexate. However, it has not been very effective. I am using Fluocinonide gel on the spots. Some of the spots are very persistent.
Psoriasis has several treatment options.
First is local coal tar. This is messy, but it generally helps. Second is sun or UV light. This long term treatment may increase the risk of skin cancer, but it helps. Third is local steroid.