Age can be an important factor in determining the cause of illness.

The causes of illness in traditional Chinese medicine are determined by a number of factors. Some of these causes are considered external, as in the six pernicious influences: wind, cold, heat, dryness, dampness, and summer heat. Other causes are considered internal, as in the seven emotions: anger, joy, worry, pensiveness, sadness, fear, and shock. Other factors that play a role in the development of disease are diet, lifestyle, and accidents.

When the body is healthy, its various substances and energies are in harmonious balance, both internally and in relation to the external environment. When this innate vitality (true qi) and immune defenses (wei qi) are strong, it is difficult for externally contracted disease to gain a foothold, especially if the invading pathogen is weak.

 However, an exceptionally strong pathogen can overwhelm even a healthy person, especially if the person has been weakened by stress, fatigue, overwork, or other lifestyle factors. For example, a person with a strong immune system might avoid catching a cold, even if a sick person sneezes on him. However, if he drinks a test tube full of the same virus, his strong immune system will be no match for such an onslaught. On the other hand, a person with very weak wei qi can catch whatever pathogen may be around due to his or her exceptionally weak defenses. This is the reason the elderly and young children are most at risk during influenza epidemics.

This interplay between wei qi (also called good qi) and pathogenic factors (evil qi) determines whether a person gets sick, how the body responds to illness, and how long it takes for health to return.

Go to the next page to learn about the six pernicious influences in traditional Chinese medicine.

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