Radix et Rhizoma Rhei (also known as rhubarb root or Da Huang) is a herbaceous perennial plant in the knotweed family Polygonaceae that is closely related to edible rhubarb. While it is commonly used as an ornamental garden plant, it is one of the key herbs used in Traditional Chinese Medicine to restore metabolism, dispel stasis, and eliminate toxins, particularly those that have accumulated in the intestines. It considered a "yin-within-yin herb" that pushes out the old to create the new, expeling old filth in order to quiet the five yin organs.
Radix et Rhizoma Rhei has a very strong downward-directing action, strongly mobilizing the intestines and washing away accumulated obstruction. This make it useful in treating constipation or diarrhea due to clumped toxins in the intestines. However this strong downward purging action also gives Radix et Rhizoma Rhei an excellent ability to drain heat from the upper parts of the body, making it useful in conditions presenting with insomnia, hypertension, headaches, red eyes, sore throat, swollen red gums, and oral ulcers.
In addition to its strong purging action, Radix et Rhizoma Rhei also has a unique ability in activating blood circulation. This is why it is often added to classical Chinese herbal formulas when there is a need to remove blood stasis, such as is seen in irregular menstruation with little to no bleeding, postpartum pain, abdominal masses, and traumatic injuries involving bruising.
Still, Radix et Rhizoma Rheiis is generally used in combination with other herbs as a laxative to treat common constipation, particularly excess-type constipation manifesting with heat. While the herb is generally safe, it should be used with caution as certain people may experience adverse reactions (ie diarrhea, vomiting, nausea, dizziness, and abdominal pain) with improper dosing.