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[Flavor and Nature]
Bitter, cold, non-toxic. The action is descending, belonging to Yin within Yin. (Soaked in wine, it enters the Taiyang Meridian; washed with wine and stir-fried, it enters the Yangming Meridian; for other meridians, it is used raw.)

[Indications]
It moves freely without staying fixed. It purges various excess heat syndromes. It treats constipation due to large intestine dysfunction. It sweeps away heat accumulated in the intestines and stomach. It eliminates dampness in the lower Jiao. It promotes the elimination of the old and the generation of the new. It resolves retained food.
It breaks up masses (zheng) in women. It treats dysentery with red and white discharge. It addresses tenesmus and abdominal pain. In Zhang Zhongjing's Xiexin Tang (Heart-Purging Decoction), it is specifically indicated for hematemesis and epistaxis caused by "heart Qi deficiency." One might ask: if heart Qi deficiency is diagnosed, the principle dictates using tonification; why use bitter-cold purgatives instead? This misunderstanding arises from not realizing that true deficiency of the Heart's original Qi would not present with hematemesis accompanied by epistaxis. In this case, the Yang of the meridian is hyperactive to an extreme degree without sufficient support, causing Yin blood to act recklessly and fly out of its vessels. Therefore, Dahuang (Rhei Radix et Rhizoma) should be used to purge the hyperactive fire, restoring harmony so that the blood returns to its vessels and calms down. Furthermore, it is said that Dahuang purges "Heart Excess" and clears pathogenic fire from the blood aspect of the four meridians. What is the meaning of this? Generally, when the Yin Qi of the Shaoyin Heart Meridian is insufficient, Heart Fire blazes fiercely. Pathogenic factors take advantage of the deficiency to knot in the Upper Jiao. The upper part of the Stomach is connected to the Heart; thus, "purging Heart Excess" essentially means "purging the Spleen and Stomach." Additionally, prolonged insufficiency of Heart Yin causes the Lungs and Liver to suffer from fire, leading to disease. Huangqin (Scutellariae Radix) assists Dahuang to rescue the Lung; Huanglian (Coptidis Rhizoma) assists Dahuang to rescue the Liver. The Lung is the master of Yin; the Liver is the mother of Yin. Blood resides in the Liver. Once the fire in the Lung recedes, Yin blood naturally restores its former state. Thus, "purging Heart Excess" essentially means "purging the Liver and Lung." For diseases located in the Qi aspect, as well as cases of Stomach Cold, Blood Deficiency, pregnancy, and postpartum periods, one must be cautious and not use it lightly. Indiscriminate use may damage Yuan Qi (Original Qi) and consume Yin blood.

[Flavor and Nature]
Bitter and acrid, warm, non-toxic. The action is descending, belonging to Yin. It enters the Jueyin and Shaoyang Meridians. It treats diseases of the Liver and Gallbladder.

[Indications]
It treats Qi stagnation. It directs food downward and breaks up accumulations. It dispels various dampness in the lower Jiao. It treats stagnant Qi in the Liver Meridian located in the left hypochondrium. It treats hernia pain in the lower abdomen. It reduces breast swelling. In Qingpi Tang (Green Peel Decoction), Qingpi (Aurantii Fructus Immaturus) is used to treat conditions where chronic malaria with severe heat leads to the formation of mass-like lumps (pi). This is likely to ventilate and regulate Liver pathogenic factors and reduce their solid accumulation. However, if there is stagnant Qi, it breaks the stagnation; if there is no stagnant Qi, it damages True Qi. Therefore, it must be selected and used with great caution. It is also stated that when Qingpi is charred black, it can enter the Blood aspect. Qingpi can also induce sweating; therefore, it should not be used in patients who already have spontaneous sweating.