Five Phase Theory extends Yin-Yang Theory, in which all things in nature are classified into five basic element types: Fire, Earth, Metal, Water, Wood. By applying this theory to people, we can better understand how disease affects each of us individually. It can be used to develop a course of therapy, as well as to recommend certain diet and lifestyle choices to support health.
Disease is caused by a Yin-Yang imbalance. Factors that can lead to disharmony include the six evils, seven emotions as well as miscellaneous factors.
The six evils: wind, cold, summer heat, dryness, dampness and fire, are related to the seasons or working environment. 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. The six climatic evils enter the body causing disease mostly through the spaces located between skin and muscle, or the openings like nose and mouth and are therefore also called the six exogenous or outside evils.
The Suwen says:.
"The five yin-organs of the human body produce five kinds of essential qi, which bring forth joy, anger, grief, worry, and fear." .
The seven emotions: joy, anger, anxiety, pensiveness, grief, fear and fright are considered the major internal causes of disease. Emotional activity is normal, internal, physiological response to stimuli from the external environment. However, when emotions become so strong that they become out of control and overwhelm a person, they can cause serious harm to the internal organs related to the emotional activity, i.e. the heart can be damaged by excessive joy, the liver by anger, the spleen by anxiety, the lungs by pensiveness and the kidneys by fear. .
Although each of us is made up of a combination of all the five phases, there is one phase which is dominating; "the source from which our deepest impulses issue forth.