After studying the cause and mechanism of the itching with the perspective of chronic medical books including Neijing, and the annotators, the conclusions are as follows. 1. The itching, which has correlation with the heart, is the deficiency symptom(虛症). It is generated when the lung-metal(肺金) is infected by the fire pathogen(火邪) and developed to depression(鬱), because of the heart fire flaming upward of circuit year(歲火太過). The treatment is to make metal depression scatter(金鬱泄之). 2. The itching occurs between the dermis(膚) and the epidermis(皮). 3. The itching generates when the excess of yang exuberance(熱盛極) precede the transmission of the wind-heats(風熱), the wind-cold(風寒), and the wind-dampness(風濕). It causes the blood deficiency(血虛) and the blood stasis(血瘀) because of the skin dryness. 4. The itching usually generates during summer, causes the body fever(身熱) and the dermis pain(膚痛). When it becomes worse, it causes generalized itching and vesicles at the whole body(浸淫). 5. The itching is related to the spirit(魄), which works in unconsciousness and the movement of defense qi(衛氣) in night.