The occurrence, development and change of disease involve a number of factors, including individual difference, geographical environment and seasonal variations which may affect the nature, duration and treatment of disease. So in treating disease, apart from following the principles of concentrating treatment on the root cause, strengthening healthy qi and eliminating pathogenic factors as well as regulating yin and yang, one has to make corresponding changes according to individual condition, local environment and seasonal variations.

Abidance by individuality means to decide treatment according to the age, sex, constitution and living habits of the patients.

The physiological functions and the state of qi and blood vary with the age, so the use of herbs has to follow such variations. Generally speaking, infants are vigorous in physiological functions, but their qi and blood are not sufficient yet and their viscera are delicate. For this reason, infants are easy to be affected by cold and heat and tend to have deficiency or excess problems. Once they fall ill, their pathological conditions are prone to change. So in the treatment of infantile disease, drastic herbs are forbidden to use and tonic herbs should be used infrequently with small dosage. 

In selecting prescription form and taking method, the characteristics of infants have to be taken into consideration. As to the old people, their physiological functions, qi and blood have all declined, so they are easy to have deficiency problems. For the treatment of old people, purgation should be used with great care even for treating excess syndrome because their constitution is weak. Since qi and blood in the aged have declined, their reaction to herbs is slow. So the treatment of deficiency syndrome for the aged with nourishing therapy needs large dosage of herbs and longer course of treatment.

Different sex has different physiological characteristics. TCM emphasizes that women are different from men because they have menstruation, leukorrhage, pregnancy and labor which have to be taken into consideration in treating women diseases. For example, herbs used during menstruation should not hinder menses, avoiding the use of herbs of cold and astringent nature; herbs used after menstruation mainly concentrate on supplementation because the vessels are deficient because of menses; 

During pregnancy, cares should be taken to protect fetus and herbs for drastic purgation, breaking blood and lubrication or herbs tending to migrate or poisonous herbs should not be used or used with great care; after labor, qi and blood are seriously deficient, cares should be taken to supplement more and purge less. 

If there is lochiorrhea, warming and supplementing therapy can be used to dredge and disperse, cold tonifying and astringing therapy should not be used lest lochia be retained. Since the liver is regarded as the congenital base of life for women and liver-qi is easy to stagnate, the treatment of women diseases often needs to soothe and regulate liver-qi.

There are different types of constitution which should be treated by different herbs. Generally speaking, strong constitution bears more purgation but less tonification, so it can be treated with large dosage of herbs for purgation but small dosage of herbs for tonification; weak constitution bears more tonification but less purgation, so it can be treated with small dosage of herbs for purgation but large dosage of herbs for tonification.

For the treatment of people with frequent predomination of yang or frequent deficiency of yin, warm-natured herbs should be used with great care lest fire be strengthened or yin be impaired. For the treatment of people with frequent deficiency of yang or frequent predomination of yin, cold-natured herbs should be used with great care lest yang-qi be impaired or phlegm be caused.  

Different living habits may exert different effect on constitution. For example, frequent indulgence in drinking of wine may cause insufficiency of liver-yin complicated by phlegm-dampness encumbering the spleen; frequent food partiality tends to cause decline of qi and blood or disharmony between yin and yang; lack of physical exercise often leads to hypofunction of the viscera and slow flow of qi and blood. People in different regions, countries and nations differ greatly in living habits. Such a difference in living habits can be used as evidence to analyze their types of constitution.

People in different regions differ in physiological functions and pathological changes because of geographical location, weather condition and living habits. Take China for example. The plateaus in the west regions are cold and dry with insufficient rain. People live in the mountains, mainly taking milk and meat. So their constitution is strong and their muscular interstices are dense, making it difficult for pathogenic factors to invade them. 

When attacked by exogenous pathogenic factors, they can be treated by dispersing therapy with large dosage of herbs for relieving the superficies. The regions in the east and south and along the seas are low and warm with sufficient rain. People live beside water and mainly eat fish and rice. Their constitution is weak and their muscular interstices are loose. So they are easily to be invaded by exogenous pathogenic factors. When attacked by exogenous pathogenic factors, they can be treated by dispersing therapy with small dosage of herbs for relieving superficies.

Seasonal variation means deciding treatment according to seasonal changes of weather. Seasonal variations of weather exert certain effect on the physiological functions and pathological changes of the body. Generally speaking, the muscular interstices are loose in spring and summer because the weather becomes warmer and warmer and yang-qi gradually elevates. So herbs acrid in taste and warm in nature cannot be used in large dosage even for wind-cold attack, avoiding excessive purgation and damaging qi and yin. 

In autumn and winter, the muscular interstices are dense because the weather becomes colder and colder, yin becomes predominant and yang deficient. In these two seasons cold-natured herbs should be used with great care except great heat syndrome. In Huangdi Neijing such a use of herbs according to seasonal variation is summarized as "avoiding using cold-natured herbs in winter, cool-natured herbs in autumn, warm-natured herbs in spring and hot-natured herbs in summer."

TCM analyzes the five zang-organs according to the four seasons, believing that liver-qi is predominant in spring, heart-qi is predominant in summer, spleen-qi is predominant in late summer, lung-qi is predominant in autumn and kidney-qi is predominant in winter. In each season one zang-organ is in predomination, the zang-organ that it generates is promoted while the zang-organ that it dominates is restricted. 

Only when such a corresponding change of the five zang-organs in the four seasons and their interrelationships have been taken into consideration in treating disease can damage of healthy qi and promotion of pathogenic factors be avoided. Besides, interrelationships among the five zang-organs in the four seasons also can be used to decide therapeutic principle and select herbs. 

Take spring for example. In spring, liver-qi is predominant, but spleen-qi must be restricted. So patients with frequent deficiency of the spleen have to be treated by strengthening spleen-qi in spring. Since predomination of liver-qi can reinforce heart-qi, the syndrome of heart-qi deficiency can be more effectively treated in spring. If it is treated in winter, the therapeutic effect is not so easy to obtain because heart-fire is restricted by kidney-water.