Four properties of Chinese medicinal herbs, cold, hot, warm and cool, are also called the four natures or four xing in TCM. Cold-cool and warm-hot are two completely different categories of natures, cold-cool belonging to yin, and warm-hot to yang, whereas cold and cool or hot and warm are only different, to some degrees, in their variance. Chinese medicinal herbs with cold-cool nature can clear away heat, purge fire and eliminate toxic materials, which are mainly used for heat-syndrome; Chinese medicinal herbs with warm-hot nature have the actions of expelling cold and restoring yang, which are mainly used for cold-syndrome.
In addition, there are also some Chinese medicinal herbs known as neutral ones whose cold or hot nature is not so remarkable and whose action is relatively mild. But actually they still have differences in the tendency to cool or warm so that they are still in the range of four natures.
The four natures -- cold, hot, warm and cool are summarized mainly from the body's response after Chinese medicinal herbs are taken, which are so defined in relation to the properties, cold or heat of the diseases treated. After Huanglian (Rhizoma Coptidis) and Shigao (Gypsum Fibrosum) are taken, the manifestations of heat-syndromes such as high fever, dysphoria, thirst and profuse perspiration can be eliminated, which indicates that Huang-lian (Rhizoma Coptidis ) and Shigao (Gypsum Fibro-sum) are cold in nature. According to the same reason, after Fuzi (Radix Aconiti Lateralis Praeparata ) and Ganjiang (Rhizoma Zingiberis) are taken, the manifestations of cold-syndromes such as aversion to cold and cold limbs, cold and painful sensation in gastric region and diarrhea can be relieved, which indicates that Fuzi ( Radix Aconiti Praeparata ) and Ganjiang ( Rhizoma Zingiberis ) are hot in nature. Treating diseases with Chinese medicinal herbs is to make use of their cold or hot nature to correct the phenomena of overabundance of heat or cold in the body to restore them as much as possible to the normal state. Therefore, on the base of syndrome differentiation, you must distinguish heat or cold nature of disease, and have a good understanding of the cold or hot property of Chinese medicinal herbs, and then selectively apply corresponding medicinal herbs so that you can achieve the desired results. Ganjiang (Rhizoma Zingiberis) and Huang-lian (Rhizoma Coptidis) can both be used to treat diarrhea but Ganjiang (Rhizoma Zingiberis) is hot in nature, therefore, used to treat diarrhea of cold type while Huang-lian (Rhizoma Coptidis) cold in nature is indicated for diarrhea of heat type. If you don't consider their proper-ties, cold or hot, when you apply medicinal herbs to treat heat or cold syndromes respectively with hot or cold medicinal herbs, you cannot achieve desired results of treatment and even bring about harmful results.
The five flavors of Chinese medicinal herbs refer to the five different tastes, pungent, sweet, sour, bitter and salty, which can be tasted by the tongue. With the development of the theory dealing with the medicinal properties, some flavors are summarized out of clinical actions of Chinese medicinal herbs; therefore, there is a little difference between the flavors of medicinal herbs and the tastes got by tongue. The Chinese medicinal herbs with same flavor mostly possess similar actions while the medicinal herbs with different flavors show different actions in the treatment, which are shown as follows.
Pungent：Pungent is a flavor of medicinal herbs that has an action of dispersing and promoting circulation of qi and blood. Pungent medicinal herbs are generally indicated for exterior syndromes due to invasion of exogenous factors and syndromes of stagnation of qi and blood. For example, Zisuye (Folium Perillae) and Bohe (Herba Menthae) can produce the effects of inducing sweating to expel the exogenous pathogenic factors from the exterior, and Muxiang (Radix Aucklandiae) can circulate qi and Honghua (Flos Carthami) can promote blood circulation.
Swoot：Sweet flavor has the nourishing, harmonizing and moistening actions. Those sweet in flavor are generally indicated for deficiency syndromes, incoordination between the spleen and stomach, certain pain syndromes, constipation due to intestine-heat, cough due to lung-heat, etc.. For instance, Huangqi (Radix Astragali) and Shudihuang (Rhizoma Rehmanniae Praeparatae) have nourishing action, Gancao (Radix Glycyrrhizae) can relieve spasm and pain, and Fengmi (Mel) can moisten the intestine and promote purgation.
Sour：Sour flavor has absorbing, consolidating and astringent actions. Those sour in flavor are often used to treat incessant perspiration, chronic cough, chronic diarrhea, emission, spermatorrhea, enuresis, frequent micturition, prolonged metrorrhagia and metrostaxis, and prolonged leukorrhea, etc., caused by loss of essence due to asthenia of healthy qi. For example, Wumei (Fructus Mume) and Wuweizi (Fructus Schisandrae) are used to relieve cough and diarrhea； Shanzhuyu (Fructus Corni) and Jinyingzi ( Fructus Rosae Laevigatae) are used to relieve emission and enuresis.
Bitter：Bitter flavor has the actions of drying or resolving dampness, purging and lowering. Those bitter in flavor are used in wide range and often used for constipation due to fire-heat, dysphoria, cough due to adverse rising of lung-qi, damp-heat or cold-damp syndrome. For example, Huanglian (Rhizome Coptidis) can clear away heat and dry dampness, and Cangzhu (Rhizoma Atractylodis) can dry dampness due to its bitter flavor and warm nature, Dahuang (Radix et Rhizoma Rhei ) can cause downward discharge, Xingren ( Semen Pruni Armeniacae) can lower and disperse lung-qi and Zhizi (Fructus Gardeniae) can clear away heat and purge fire.
Salty: Salty flavor has the effects of softening hard nodes or masses and promoting defecation, etc., so salty medicinal herbs are often used for the syndromes such as scrofula, superficial nodule, abdominal mass and internal accumulation with dry stool. For example, Haizao ( Sargassum ) and Kunbu ( Thallus Laminariae et Eckloniae ) can disperse scrofula, and Mangxiao (Natrii Sulfas) can relieve constipation by purgation.
In addition to the five flavors that are the basic tastes of Chinese medicinal herbs, there are also astringent and bland flavors. TCM holds that astringent flavor falls under the sour flavor category and bland flavor falls under the sweet, so they are still included in the five flavors. The actions of astringent flavor are very similar to those of sour flavor, which all have astringent action. For example, Longgu (Os Draconis ) and Mull ( Concha Ostreae) can stop nocturnal emission, leucorrhea and profuse perspiration; Chishizhi ( Halloysitum Rubrum ) and Yuyuliang (Limonitum) can arrest diarrhea. Those bland in flavor such as Zhuling (Polyporus) and Fuling (Poria) possess the actions of removing dampness and promoting diuresis, and are often used for edema and dysuria.
The nature and flavor are two kinds of medicinal properties that every Chinese herb possesses, and each of Chinese medicinal herbs must have the both properties. The natures and flavors deal with the pharmacological properties separately in different aspects. Only when you have a good understanding of the actions of both the natures and flavors, and combine them with each other, can you correctly understand their medicinal effects. Those with same natures and flavors possess essential similar actions. Therefore, different natures and flavors of medicines result in their different actions. For instance, Huanglian (Rhizoma Coptidis) and Huangqin (Radix Scuteltariae) bitter in flavor and cold in nature, both can clear away heat and relieve toxic materials, purge fire and dry dampness; Huanglian (Rhizoma Coptidis) and Ganjiang (Rhizoma Zingiberis), of which Huanglian (Rhizoma Coptidis) is a kind of Chinese medicinal herbs bitter in flavor and cold in nature but Ganjiang (Rhizoma Zingiberis) is pungent in flavor and warm in nature are completely different in their actions. Ganjiang (Rhizoma Zingiberis) can expel cold, warm the middle energizer, restore yang, stop bleeding and warm the lung to resolve fluid retention, whose actions are completely different from those of Huanglian (Rhizoma Coptidis). If the Chinese medicinal herbs are similar in nature but different in flavor; or similar in flavor but different in nature, their actions are both similar and different. For instance, both Huanglian (Rhizoma Coptidis ) and Shengdihuang ( Radix Rehmanniae) are cold in nature and both can clear away heat, but being bitter in flavor, Huanglian (Rhizoma Coptidis) possesses the action of drying dampness while Shengdihuang ( Radix Rehmanniae ), sweet in flavor, can promote the production of the body fluids. Therefore, Huanglian (Rhizoma Coptidis) can clear away heat and dry dampness and is indicated for damp-heat syndrome. Whereas, Shengdihuang (Radix Rehmanniae) can clear away heat and promote the production of the body fluids so it is indicated for consumption of the body fluids due to heat. Another example, both Shengjiang (Rhizoma Zingiberis Recens) and Bohe (Herba Menthae) are pungent in nature and possess dispersing action. But being warm in nature, Shengjiang (Rhizoma Zingiberis Recens ) can eliminate cold while Bohe (Herba Menthae), cool in nature, can clear away heat. Therefore, Shengjiang (Rhizoma Zingiberis Recens) is indicated for exterior syndrome due to wind-cold while Bohe (Herba Menthae) for exterior syndrome due to wind-heat. In a word, when the properties of Chinese medicinal herbs are distinguished, their natures and flavors cannot be separately considered.
[PDF] Four natures and five flavors