2.3.1　Psoriasis

Psoriasis is a common，chronic and recurring inflammatory skin disease.The typical lesions are scaly plaques and papules.The disorder may occur at any age without gender predominance，but it is more common in young adults.The prevalence of natural population varies between 0.1％and 3.0％，and the incidence of psoriasis in China is 0.123％.Psoriasis is prone to relapse or aggravate in spring and winter，and tend to relieve in summer and autumn.(https://www.daowen.com)