(1) The diseases caused by the six climatic evils are mostly related with seasons and living or working environments. For example, generally, there are wind diseases in spring, summer-heat diseases in summer, damp diseases in late summer and early autumn, dry diseases in autumn and cold diseases in winter. In addition, "people who live for an extended period of time in a damp environment tend to be easily attacked by the damp evil, and those who work long in an environment of high temperature tend to be easily attacked by the dry-heat evil or fire evil.

(2) All of the six evils can act either alone or in a combination of two or more in attacking the human body. Such syndromes as common cold of wind-cold type, damp-heat diarrhea, wind-cold-damp blockage, etc., are examples of medical problems caused by the composite evils.

(3) In the course of causing diseases, any one of the six climatic evils not only can be influenced by the others, but also can be transformed into another kind of evil under certain conditions. For example, the cold evil that enters the interior of the body can be transformed into the heat evil, and the long-persisting summer-heat with dampness can be transformed into dryness, causing yin consumption.

(4) In most cases, the six climatic evils get into the body and cause diseases through the skin and muscle, or the mouth and nose, or through both ways; so they are also termed "the six exogenous evils."

In today's clinical practice, the syndromes and diseases caused by the six climatic evils also include the pathological problems produced by biological factors (bacteria, virus, ete. ), chemical factors, and so on. At a minimum, TCM's study of the cause and course of disease should take all the exogenous etiological factors which can be classified according to the clinical manifestation of the six climatic evils, and the body's pathological responses to them, into consideration. Although this concept needs refining, it is an acceptable beginning approach.

Besides the exogenous syndromes caused by the six climatic evils, there also are syndromes caused by the transformed wind, transformed cold, transformed dampness, transformed dryness, transformed heat, and transformed fire produced by the viscera when in dysfunction. Although their clinical manifestation is similar to that of the syndromes caused by the six climatic evils, they are not caused by the exogenous evils. In order to differentiate between the two categories of syndromes, the transformed evils by the viscera in dysfunction are called "the five endogenous evils," i.e. endogenous wind, endogenous cold, endogenous dampness, endogenous dryness, and endogenous fire (or heat). The pathological effects of these transformed endogenous evils will be introduced later in a section entitled "The Five Endogenous Evils."