Exogenous evils   Exogenous evils or environmental pathogens are the six natural climatic factors: wind, cold, summer-heat, dampness, dryness, and fire. They represent the natural conditions within which all living things exist and are not harmful under normal conditions. They become pathogenic or disease factors when they are excessive or when sudden changes occur that cause an imbalance of yin and yang inside the body.		wai xie 外邪   外源性病邪又稱外邪，在中醫是指六種自然界的氣候狀況；即風、寒、暑、濕、火及燥，是萬物生長的條件，在正常情況下對人體無害。人體對氣候變化有一定的適應力，當變化過劇或機體適應力減低時，就會成為致病因素。