It refers to the highly resinous wood of Aquilaria sinensis (Lour.) Gilg. Aquilaria sinensis and Aquilaria agallocha Roxb. It is also known as agar wood, eaglewood, ales wood, oodh or agar, gaharu, aloeswood, Oud, Chen Xiang, kalamabak, jinkoh, and so on. This is simply because it grows in many countries and thus gets many different names. From the historical perspective, at least more than 10 countries and regions are still growing or ever grew some certain species of Aquilaria tree. These countries are India, Vietnam, Thailand, Laos, Myanmar, Malaysia, Singapore, Indonesia, Cambodia, and China. In China, it is mainly found in areas such as Guangdong, Guangxi, Yunnan, Hainan, Taiwan, and Hong Kong.

Since ancient times, in China there is an old saying that goes like "Chen Tan Long She", in which that "Chen" means exactly the Chen Xiang herb. The other three are Tan Xiang (Sandalwood), Long Yan Xiang (ambergris), and She Xiang (Navel Gland Secretions of Musk Deer). These four are the most popular, rare, and precious spices and incenses in the world. Unlike Sandalwood, Agarwood is not simply a timber but the solid-state condensation product that is formed by the combined action of mixed oil (gum) and the wood constituents from a special species of aromatics tree.

To be specific, Agarwood is a special kind of biochemical substances. Its formation is a step-by-step complex process. Initially the Agarwood tree trunk is invaded by a parasitic mold called Menanotus flavolives. And then the biochemical changes occur. Finally, it needs years of deposition to make it. As you may know, Agarwood has such a high density that it is submergible. This fact also shows that it coagulates a great deal of gum or balsam. Of course, the higher density often means higher quality and more expensive price in the market.

Agarwood

WHAT'S AGARWOOD USED FOR? 
In terms of Traditional Chinese Medicine (TCM), Agarwood is viewed as acrid, bitter, and warm in nature. And it covers three meridians, including kidney, spleen, and stomach. Its basic functions are to promote the Qi circulation in order to relieve pain, warm the middle Jiao to arrest vomiting, and control respiring Qi to relieve asthma. Its chief indications and uses are distention and pain in abdominal region, vomiting, hiccups and belching resulted from cold stomach, and dyspnea and rebellious Qi due to kidney deficiency. Usual dosage is from 1 to 5 grams, decocted later.

MAJOR CHINESE HERBAL FORMULAS INCLUDING AGARWOOD
1) Chen Xiang Jiang Qi Wan
From Tai Ping Hui Min He Ji Ju Fang (Formulas of the Peaceful Benevolent Dispensary), this formula is used for distention and fullness in chest and diaphragm, abdominal distension and fullness, dyspnea and tachypnea, dysphoria due to unceasing hiccups, and beriberi. Other main herbs are Xiang Fu (Nut Grass Rhizome), Suo Sha Ren (Cardamom Seed, Elettaria cardamomum), and Gan Cao (Licorice Root).

2) Chen Xiang Wan
From Ji feng Pu ji fang (Jifeng’s Formularies for universal relief), it is mainly designed for chronic deficiency of spleen and kidney, lung invading by upward retentive fluid, cough and shortness of breath, fullness in abdomen and flanks, and difficult urination. Other primary herbs include Wu Yao (Lindera Root), Fu Ling (Poria, China Root), Chen Pi (Tangerine Peel), Ze Xie (Alisma), Xiang Fu (Cyperus), and She Xiang (Navel Gland Secretions of Musk Deer).

3) Si Mo Tang
Simo decoction comes from Ji sheng fang (Formulas to Aid the Living). As its name implied, it consists of four herbs and other three are Ren Shen (Ginseng Root), Bing Lang (Betel Nut, Areca Seeds), and Wu Yao (Lindera). And it is a famous prescription for internal injuries caused by seven emotions, wheezing due to abnormal rising of Qi, and appetite loss because of dysphoria.