Skin is the largest organ of the human body, skin diseases are mainly related to the skin, the main manifestation is skin damage, but some skin diseases can cause damage to other organs. 1. Diseases mainly manifested by skin injury: these diseases often take skin injury as the main or only manifestation, which can be divided into infectious diseases (such as chickenpox, impetigo, ringworm, folliculitis, etc.) and non-infectious diseases (such as contact dermatitis, eczema, vitiligo, freckles, etc.) according to the etiology. 2. Skin diseases accompanied by other organ damage: these diseases are mainly skin manifestations, but at the same time accompanied by other multi-organ damage, such as severe drug rash can cause liver function abnormalities, etc., allergic purpura can cause kidney function abnormalities. In addition, some diseases can involve multiple systems, organs, can also appear skin manifestations, common in rheumatic immune diseases, such as systemic lupus erythematosus can appear on the face of butterfly-shaped erythema, systemic sclerosis can appear skin sclerosis and so on.