Yi medicine is the traditional medicine of the Yi people, distributed in Chuxiong, Yunnan and Liangshan, Sichuan. Yi medicine divides the primordial energy of heaven and earth into two types: clear and turbid, and generates the five elements of gold, wood, water, fire and earth as basic substances. The human body uses clear energy to connect the chest, abdomen and five internal organs, and uses turbid energy to circulate the skin, abdomen and back. The six qi are connected from top to bottom to balance the internal and external evil poisons. This is the Yi people's understanding of life and health, and has become the basic theory of Yi medicine. Water plaster therapy is an external treatment method for clearing heat and detoxifying. The climate in the Yi area is hot and humid, insects, mosquitoes and midges are harmful, malaria and epidemic gas are poisonous, and carbuncles and ulcers occur from time to time. Water plaster therapy uses well water or ice water and snow water (collected in winter or from the mountains and stored in earthenware jars for use) to mix herbs and apply them to the affected area. When the boils and sores have not yet broken, chop one or more herbs into pieces, add well water or ice water or snow water to make a paste, apply to the red, swollen, hot and painful parts, wrap with gauze, and change it every 12 days. The herbs used, such as green leaf gall, ground gall, winter jasmine, wild chrysanthemum, etc., plus the water is cool, have the effects of clearing heat, detoxifying, reducing swelling and relieving pain.