The four qi refers to the four different medicinal properties of the drug: cold, hot, warm and cool. It is an important medicinal theory that corrects the rise and fall of yin and yang in the human body by regulating the changes of cold and heat in the body, and is an important medicinal theory to explain the nature of the drug.

The understanding of the four qi originated very early. "Han Shuyi Wenzhi Fang Technique" said: "The scriptures, the cold and temperature of the materia medica, the shallow and deep of the disease, the taste of fake medicine, the appropriateness of the sense of qi, distinguish the five hardships and six hardships, and cause the Qi of water and fire, to open and close the knots, and vice versa." "It can be known that the medicinal properties are divided into cold and temperature, not later than the Western Han Dynasty. The text also pointed out that the cold and heat of medicinal properties are formed by "the appropriateness of the sense of qi", so the "Benjing" first proposes that "there are four qis: cold, hot, warm and cool". It can be seen that the four qi of the earliest medicinal properties are summarized by the characteristics of the four seasons of climate. However, in order to avoid confusion with the smell of medicine, Kou Zongzao of the Song Dynasty advocated changing the "four qi" to "four natures". Li Shizhen also said from it, saying that "Kou's words are cold, hot, warm and cold are sexual, and fragrant and smelly and fishy are gas, which is consistent with the text of "The Book of Rites". But since "Su Wen", only the smell of words, pawn can be changed, so from the old. ”。 Although the arguments of Kou and Li are reasonable, they fail to explain the original meaning of the four qis.

The medicinal properties of the four qi are also the same as the five flavors, which have the attributes of yin and yang, that is, cold is yin, and warm is yang. Cold and warm are two opposing medicinal properties, while the difference between cold and warm is only in degree, that is, "cold is second to cold" and "warm is second to heat". Some Materia Medica literature also describes the four characteristics of drugs with "great heat", "great cold", "slightly warm" and "slightly cool", which is a further distinction between the different degrees of the four qi of traditional Chinese medicine, and shows that it should be used at discretion. In addition, there is a class of flat drugs in addition to the four sexes, which refers to a class of drugs with cold and heat properties that are not obvious, have peaceful properties, and have a milder effect. In general, the efficacy of flat drugs is mainly reflected through the five flavors and other medicinal properties.

The cold, heat, and warmth of the medicine are summarized by the different reactions and different curative effects of the drug on the human body, which is relative to the nature of the disease being treated. If the patient presents with high fever and thirst, red face, sore throat, and pulse number, this belongs to the yang heat syndrome, and the above symptoms can be alleviated or eliminated after treatment with gypsum, zhimu, gardenia and other drugs, indicating that their medicinal properties are cold; On the contrary, if the patient presents with cold limbs, paleness, cold pain in the abdomen and abdomen, and a slight pulse, this belongs to the cold syndrome, and the above symptoms can be relieved or eliminated after treatment with drugs such as aconite, cinnamon, and dried ginger, indicating that their medicinal properties are warm.

Generally speaking, cold medicine has the functions of clearing heat and purging fire, cooling blood and detoxifying, nourishing yin and removing steam, diarrhoea and laxative, clearing heat and water, clearing heat and phlegm, clearing the heart and opening the body, cooling the liver and relieving wind, etc.; The warm medicine has the functions of dissipating cold in warmth, warming the liver and dispersing knots, replenishing fire and helping yang, warming yang and improving water, warming meridians and channels, returning fire to the source, and returning to yang to save adversity

"The cold is hot, and the hot is cold", and the preface of the "Benjing" "Treating cold with hot medicine, treating heat with cold medicine" points out how to grasp the principle of the four qi theory of drugs to guide clinical medication. Specifically, warm medicine is mostly used to treat a series of cold and cold syndromes, such as cold abdominal pain, cold hernia pain, impotence, uterine cold infertility, cold edema, wind and cold paralysis syndrome, blood cold amenorrhea, deficiency yang superiority, and death yang prostration; The cold medicine is mainly used for a series of yang heat syndromes, such as real heat and thirst, warm poison spots, blood heat vomiting, fire poison sores, hot constipation, hot drenching and astringent pain, jaundice edema, phlegm heat, wheezing and coughing, high fever and dizziness, and heat and wind. In short, cold and cold medicine to treat yang and heat syndrome, and warm and warm medicine to treat yin and cold syndrome, which is a clinical medication principle that must be followed. On the contrary, if cold medicine is used for the yin and cold syndrome, the use of warm medicine for the yang heat syndrome will inevitably lead to further deterioration of the condition and even cause death. Therefore, Li Zhongzi's "Medical Sect Must Read" said: "Cold and hot and warm and cold, a dagger is fallacious, and it is difficult to recover water." ”

Because there is a procedural difference between cold and cold and hot temperatures, it is also necessary to pay attention when taking medication. If hot medicine is used instead of warm medicine, and cold medicine is used when cold medicine is used, the serious illness and light medicine cannot achieve the purpose of curing the disease; On the contrary, when warm medicine is used and hot medicine is used, it will hurt its yin, and when cold medicine is used instead of cold medicine, it is easy to damage its yang. As for the complex symptoms of cold and heat, it should be used as a combination of cold and heat medicine to make cold and heat harmonize. In particular, it is necessary to distinguish the true and false of cold and heat, and if there is evidence of true cold and false fever, it should be treated with hot medicine; The evidence of true heat and false cold was also selected to be cured with cold medicine. Don't confuse the real with the fake.

Since each drug has sex and taste at the same time, it is essential to combine the two. Miao Xiyong said: "If there is a taste, there must be gas, and there is gas and sex", emphasizing that medicinal properties are composed of qi and taste. In other words, it is necessary to combine the four qi and the five flavors in order to accurately identify the effect of the drug. Generally speaking, the smell is the same, the effect is similar, and most of the same class of drugs are like this, such as Xinwen drugs have the effect of diverging wind and cold, and sweet and warm drugs have the effect of replenishing qi and helping yang. Sometimes the smell is the same, and there is a difference between primary and secondary, such as astragalus sweet and warm, biased to be willing to replenish qi, locked yang sweet and warm, and biased to warm to help yang. The smell is different, the effect is different, such as Coptis chinensis bitter cold, Codonopsis radix sweet and warm, Coptis chinensis has the function of clearing heat and dampness, and Codonopsis ginseng is tonifying and invigorating qi. The effects of the drugs represented by those with the same smell and different tastes are different. For example, ephedra, almonds, jujubes, black plums, and cistanche all belong to the warmth, due to their different tastes, and the effects are different, such as ephedra bitter and warm to dispel cold and relieve the surface, almonds to relieve cough in bitter temperature, jujube to nourish the spleen and invigorate qi, black plum acid to warm the lungs and intestines, cistanche salty and warm to nourish the kidney and help yang; For example, cinnamon branches, mint, aconite, and gypsum are all pungent flavors, because the four qi are different, and there are cinnamon branches with pungent warmth to dissolve the surface and dissipate cold, mint pungent and cool to evacuate wind and heat, aconite pungent heat to supplement fire and help yang, gypsum pungent cold to clear heat and reduce fire and other different effects. If there is also a medicine with several flavors, it indicates that the treatment range is larger. For example, Angelica sinensis is sweet and warm, willing to replenish blood, Xin to invigorate blood and move qi, and warm to dispel cold, so it has the functions of replenishing blood, invigorating blood, relieving pain, warming meridians and dispersing cold, etc., and can be used to treat a variety of diseases caused by blood deficiency, blood stagnation and blood cold.

In general, clinical medication is to use both its qi and its taste, but sometimes when it is combined with other drugs, there may be different situations of using its qi or its taste. If cimicifuga is sweet and slightly cold, when it is used with astragalus to treat the depression of central qi, its sweet taste is taken to enhance the effect of yang qi; If it is used with Pueraria lobata to treat measles, take its pungent flavor to relieve the episare; If it is used with gypsum to treat stomach fire and toothache, take its cold nature to clear heat and reduce fire. This is the so-called "decoction of herbal medicine" by Wang Haogu: "The pungent, sweet, sour, bitter, salty, and taste of medicine; Cold, hot, warm, cool, and airy. The taste is five, the gas is four, and among the five flavors, each flavor has four gases, there are those who make the qi, there are those who make the taste, and there are those who make the smell...... It is also used in different ways. Therefore, it is necessary to be familiar with the general laws of the four qi and five flavors, and to master the special therapeutic effect of each drug odor and the law of odor coordination, so as to have a good grasp of the medicinal properties and guide clinical medication.