Psoriasis, commonly known as “psoriasis”, is a common chronic, relapsing, inflammatory skin disease. There are three main features in the pathogenesis of psoriasis: abnormal differentiation, hyperproliferation of keratinocytes and inflammatory response. Epidermal overgrowth is the basic pathological process of psoriasis, so psoriasis is not contagious and the lesions are sterile. However, the occurrence of psoriasis is the result of a combination of genetic and environmental factors. About 1/3 of psoriasis patients have family history, and when one parent has psoriasis, the incidence of psoriasis in their children is about 16%; when both parents have psoriasis, the prevalence of psoriasis in their children reaches 50%. In addition, upper respiratory tract streptococcal infection and mental stimulation, cold and other factors can also induce and aggravate psoriasis.