Psoriasis is a long-lasting (long-term) skin disorder that is autoimmune that triggers a rapid production of skin cells that are not mature, which can result in skin lesions, redness as well as inflamed spots. It is not infectious and is caused by the immune system, genetics disorders as well as stress, infections, and environmental triggers. The psoriasis patches can appear anywhere on the skin, such as the knees, scalp, and back.