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Paeoniae Radix (Shaoyao) has a slightly cold nature and an acid and bitter taste. Its qi is thin while its flavor is strong, belonging to Yin, governing descent, representing Yang within Yin. It possesses slight toxicity.
It enters the Hand-Taiyin Lung Meridian and Foot-Taiyin Spleen Meridian.
Li Gao (cited as *Xiang*) states: Paeoniae Radix is a herb that tonifies the Middle Jiao. When used with Zhi Gancao (Honey-fried Licorice Root) as an assistant, it treats abdominal pain. In summer, for abdominal pain, add a small amount of Huangqin (Scutellaria Root); if abdominal pain is accompanied by aversion to cold, add 1 qian of Rougui (Cinnamon Bark), 3 qian of Bai Shaoyao (White Peony Root), and 1.5 qian of Zhi Gancao (Honey-fried Licorice Root). This is a divine prescription from Zhang Zhongjing. For severe cold-induced abdominal pain in winter, add 2.5 qian of Guizhi (Cinnamon Twig), two cups of water, and decoct until half remains. Use the peeled root.
Zhang Yuansu (cited as *Xin*) states: Paeoniae Radix is a herb for the Spleen Meridian; it collects Yin Qi and can relieve abdominal pain. The acid flavor collects and secures, supporting Yang while collecting Yin Qi, draining pathogenic factors, and supporting Yin. Used together with Shengjiang (Fresh Ginger), it warms the meridians, disperses dampness, unblocks obstruction, relieves abdominal pain, regulates Stomach Qi stagnation, and addresses Lung dryness and heat. The combination of acid astringency and sweet moderation makes it an essential herb for treating diarrhea (Xiali).
Lei Xiao (cited as *Zhen*) states: White Paeoniae Radix tonifies, while Red Paeoniae Radix disperses; it drains Liver Fire and tonifies the Spleen and Stomach. Soaked in wine, it promotes circulation in the meridians and stops pain in the middle abdomen.
*Shennong Bencao Jing* (Divine Farmer's Materia Medica) states: It primarily treats abdominal pain caused by pathogenic factors, removes blood bi (obstruction), breaks down hard accumulations, and treats cold-heat hernia and jia masses; it stops pain, promotes urination, benefits Qi, unblocks blood vessels, moderates tension, dissipates evil blood, and drives out thief blood; it removes fluid retention and promotes bladder function.
Kou Zongshi (cited as *Yanyi*) states: Paeoniae Radix uses the whole root, which comes in many varieties. One must select those with red flowers and single leaves; those from mountains are superior, as excessive foliage results in hollow roots. However, its roots are mostly reddish and have an astringent taste. Those that are white, thick, and plump are also good, with other details as described in the classics. However, individuals with Blood deficiency and Cold constitution should avoid this herb. As the ancients said: "Reduce Shaoyao to avoid Middle Jiao Cold." This cannot be ignored. Currently, those with red flowers are called Chishao (Red Peony Root); those with white flowers are called Baishao (White Peony Root). Folk saying holds that White Shaoyao tonifies and Red Shaoyao drains.
Li Dongyuan (Dongyuan) states: Only those with an astringent taste are considered superior. Someone asked: Ancient and modern formulas often use 'astringent' to mean collecting/securing, but why does *Benjing* mention 'promoting urination'? Li Dongyuan replied: Paeoniae Radix can stop various dampnesses and benefit body fluids, allowing urine to flow naturally on its own; it is not inherently a diuretic drug, so this point should be understood. Another asked: What does 'moderating the center' (Huanzhong) mean? Li Dongyuan replied: When the Liver is damaged, one must moderate its interior tension. Asked what herb to use for treatment, Li Dongyuan said: Siwu Tang (Four Substances Decoction) should be used because it contains Paeoniae Radix. Red Paeoniae Radix promotes urination and directs Qi downward; White Paeoniae Radix stops pain and disperses Blood and Qi. It enters the Hand-Taiyin and Foot-Taiyin meridians. Generally, those with sour and astringent properties are superior, acting as agents that collect and stop dampness, thus governing the Hand-Taiyin and Foot-Taiyin meridians. Being of a collecting and descending nature, it can reach the Sea of Blood and enter deep below, finally entering the Jueyin Meridian. Later generations used Red Shaoyao to drain and White Shaoyao to tonify because white corresponds to the West (Metal/Lungs) hence tonifying, and red corresponds to the South (Fire/Heart) hence draining.
*Shennong Bencao Jing* states: It can promote urination. This does not mean it directly promotes urination, but because the Kidney governs both large and small bowel movements, using this herb to benefit Yin and moisten allows urine to flow freely.
*Nan Jing* (Classic of Difficult Issues) states: "When the Liver is damaged, moderate its interior." This refers to regulating Blood. Myrrh (Moyao), Xingyao (Lindera Root), and Leiwan (Omphalia Lapponica) serve as its guiding herbs (Shi).
*Shennong Bencao Jing* further states: It is incompatible with Shihu (Dendrobium Stem) and Mangxiao (Natrii Sulfas). It fears Xiaoshi (Nitratum), Biejia (Testudo Carapax), and Xiaoji (Cirsii Herba). It is antagonistic to Lilu (Veratrum Root).
*Shanghan Lun* commentary (cited as *Ye*, referring to the author's context or specific text) states: Deficiency-cold pain in the abdomen belongs to the Spleen Meridian disease; without Paeoniae Radix, it cannot be eliminated. It is an agent that tonifies body fluids and stops dampness.