Psoriasis is a chronic skin condition that is often caused by stress.
Moisturizing the skin well, using anti-dandruff shampoo and getting enough sun can all help.
This balm is very rich and has often helped people:
https://www.biotylab.com/en/body/remedies-1/egyptian-magic-balm
For the hair: https://www.biotylab.com/nl/categorieen/founders-blend-scalp--hair-treatment
For the body: use soap that has a disinfectant effect: Sugar soap with Tea Tree from Dr Bronners
Very problem skin is often helped with this soap: Ayurvedic soap with 18 herbs
You can also control other risk factors such as no excessive alcohol consumption, no smoking, and a healthy diet.