The so-called five endogenous pathogenic factors are endogenous wind, endogenous cold, endogenous dampness, endogenous dryness and endogenous heat (fire). Though they are called wind, cold, dampness, dryness and heat (fire), they are actually pathogenic factors due to dysfunction of the viscera. That is why the word "endogenous" is used to modify their names.

Endogenous wind is produced by the liver, so it is usually called "liver-wind" and "internal disturbance of liver-wind". There are four factors responsible for the occurrence of endogenous wind. The first is extreme heat producing wind, referring to the disease marked by convulsion due to exuberant heat that scorches liver-yin and deprives the tendons of nourishment; the second is trans- formation of liver-yang into wind, referring to the disease marked by dizziness and infantile convulsion resulting from hyperactivity of yang transforming into wind and disturbing the upper orifices; the third is yin-deficiency stirring wind.

Referring to the disease marked by infantile convulsion and convulsion resulting from declination of liver-yin and inability of yang to hide that lead to failure of the yin-fluid to nourish the tendons; the fourth is blood-deficiency stirring wind, referring to the disease marked by muscular peristalsis and tremor resulting from failure of the deficient blood to nourish the liver and the tendons.

The occurrence of endogenous cold is due to the deficiency of yang. The deficiency-cold of the viscera can be caused by either the deficiency of the kidney-yang or the spleen-yang or heart-yang. Since the kidney-yang is the source of yang-qi in the whole body, the deficiency of the kidney-yang is the predominant factor responsible for the occurrence of endogenous cold.

Endogenous dampness results from the spleen. Usually failure of water to transform due to dysfunction of the spleen may produce the endogenous dampness which encumbers the spleen and affects the transporting and transforming functions of the spleen or accumulates into phlegm and retention of fluid, further resulting in other diseases.

Endogenous dryness results from insufficiency of body fluid and is related to yin-deficiency. Since body fluid and blood can transform into each other, the deficiency of blood also causes dryness. The manifestations of endogenous dryness are often related to the intestines, the stomach, the lung and other orifices, such as dry nose, dry throat, dry eyes, scanty urine and retention of dry feces, etc.

The causes of endogenous heat (fire) are various, such as exogenous wind, exogenous cold, exogenous dampness and exogenous dryness that all can transform into heat; mental upset and extreme changes of emotions that often turn into fire; predomination of yang and deficiency of yin that usually produce the endogenous fire and heat; and excessive qi that frequently leads to fire, etc.