My elderly father had a horrible case of psoraisis. After researching I made this salve many times for him:
1/2 cup shea butter; 1/4 c castor oil, 1/8 cup aloe, 1 oz almond oil; 1/2 t Vitamin E, 5-10 drops lavender, 5 drops tea tree, 3-4 drops Myrhh & Frankencense essential oils. Melt over low heat, mix and apply. You can also add Neem.
The massage therapist we had seeing him 2x week called to ask what it was... she was amazed at how it helped heal in in a couple months and loved the way her hands felt. The thick skin disappeared on his elbows but we didn't have the oppty to see how it worked on the scarring as he passed. Liver detox is also important.