Tan Xiang, Chen Xiang, and Mu Xiang are three trees with an exquisite aroma that have been used in traditional Chinese medicine for centuries. All these have Xiang(香) in their names, which means aroma. Each of these trees has unique properties and actions that make them valuable in the treatment of various ailments.
Chen Xiang(沈香, Aquilariae Lignum resinatum), also known as agarwood, has been referred to as the "Wood of the Gods" for thousands of years. First-grade agarwood can cost as much as $100,000 per kilogram, and its essential oil can cost up to $80,000 per liter, making it one of the most expensive raw materials in the world. It is a kind of resin of the tree. It has a warm nature and acrid and bitter taste and is associated with the Spleen, Stomach, and Kidney channels. It is used to regulate qi, relieve pain, descend qi, and relieve vomiting. It is also used to warm the Kidneys in grasping Lung qi. However, it is cautioned to be avoided in cases of sunken middle Jiao qi and hyperactive fire from yin deficiency.
Tan Xiang(檀香, Santali albi Lignum), also known as sandalwood, is commonly used as incense and has a warm nature and acrid taste. It is associated with the Spleen, Stomach, and Lung channels and is used to regulate qi and relieve pain. In Western herbology, sandalwood oil has been used as an antiseptic and astringent for the treatment of headaches. It is derived from the tree stem of the Santalum species.
Mu Xiang(木香, Aucklandiae Radix), also known as costus root, is a warm, acrid, and bitter-tasting root that is associated with the Spleen, Stomach, Large intestine, and Gallbladder channels. It is used to regulate qi, relieve pain, and strengthen the Spleen to prevent stagnation. It is particularly useful for treating symptoms of Qi stagnation of the Spleen and Stomach, including poor appetite, indigestion, food stagnation, epigastric and abdominal fullness, bloating, pain, diarrhea, and tenesmus. It can also relieve flank pain, distension, and soreness, as well as bitter taste, yellow tongue coat, and possible jaundice associated with Liver Qi stagnation.
All these three trees have a warm temperature, which makes them effective in treating cold and stagnant conditions. The acrid and bitter taste of these trees helps to move qi and relieve pain, while their association with the Spleen and Stomach channels makes them useful in treating digestive issues. The Lung, Kidney, Large intestine and Gallbladder channels are also involved in their actions, which reflect their broader therapeutic effects. Tan Xiang is used for qi stagnation combined with blood stasis, the representative formula is Dan Shen Yin. Chen Xing is used only for an emergency conditions to regulate severe qi stagnation. Nuan Gan Jiang has Chen Xiang as one of the ingredient to treat Liver qi stagnattion. Mu Xiang is most commonly used for food stagnation.