What is Cang Zhu? Is it the same as Bai Zhu, Mao Cang Zhu or Bei Cang Zhu?
Cang Zhu (苍术) is the dried rhizome of Atractylodes lancea (Mao Cang Zhu) or Atractylodes chinensis (Bei Cang Zhu). The pharmacopoeial name is Atractylodis Rhizoma. Mao Cang Zhu from the Maoshan area of Jiangsu is prized: many oil cavities and white needle crystals on standing. Bei Cang Zhu from Hebei and Shanxi is looser and less aromatic. Bai Zhu is a different species. Bai Zhu tonifies the Spleen; Cang Zhu dries dampness and mobilizes the Spleen. Older texts used one name “Zhu”; today they are not interchangeable.
What are the TCM properties and traditional uses of Cang Zhu?
According to the Chinese Pharmacopoeia, Cang Zhu is acrid, bitter and warm, enters the Spleen, Stomach and Liver channels, and acts to dry dampness and strengthen the Spleen, dispel Wind and disperse Cold, and brighten the eyes. It is used for damp obstruction of the middle with fullness and diarrhea, edema, beriberi and flaccidity, Wind-Damp painful obstruction, Wind-Cold colds, night blindness and dim vision. It is a strong aromatic dampness-transforming herb that can also release the exterior.
What is the difference between raw, bran-fried and rice-water-processed Cang Zhu?
Raw Cang Zhu is fiercely acrid and drying—stronger to dry dampness, dispel Wind and disperse Cold (Bi pain, Wind-Cold-Damp exterior). Bran-fried Cang Zhu is less harsh, more fragrant, and better to strengthen Spleen and Stomach (fullness, poor appetite, phlegm-fluid). Rice-water processing further softens dryness. Scorched Cang Zhu is used more to bind the intestine. Mobilize dampness with bran-frying; expel Wind-Damp and release the exterior with the raw form.
What is the usual dosage of Cang Zhu?
The pharmacopoeial decoction dose is 3–9 g; it may also enter pills or powders. Reduce the dose for children and those with Yin-deficiency constipation, or pair it with moistening herbs. Large amounts easily dry fluids and bind the stool. Use official slices; do not self-prescribe high-dose monotherapy or stir-fry wild rhizomes as a vegetable.
What are the contraindications of Cang Zhu?
Avoid or use caution in Yin-deficiency heat, Qi deficiency with much sweating, dry mouth and constipation. It is bitter, warm and fiercely drying. Classical texts warn that using it in blood-Qi weakness or constraint-heat can consume Qi and Blood and stir deficient fire. Use care in Asteraceae allergy. Do not self-prescribe in pregnancy. Stop if thirst, nosebleed or vexing heat appears.
How do you choose between Cang Zhu and Bai Zhu?
The teaching is: “To supplement the Spleen, use Bai Zhu; to mobilize the Spleen, use Cang Zhu.” Choose Cang Zhu when damp excess, a thick greasy coat, fullness, heaviness, Wind-Damp Bi or an exterior pattern with dampness predominate. Choose Bai Zhu when Spleen deficiency, poor appetite, fatigue, sweating or restless fetus predominate. They are often paired when deficiency and dampness coexist. A script for “Cang Bai Zhu” usually means both herbs.
Can Cang Zhu dry dampness and treat rheumatism or colds?
Yes. Middle-jiao dampness with fullness, nausea, loose stool and a greasy coat is classically treated with Magnolia bark and tangerine peel in Ping Wei San. Lower-body Damp-Heat or heavy legs may join Phellodendron, coix and Achyranthes (Er Miao, San Miao, Si Miao). Wind-Cold-Damp with chills, body ache and no sweat can use its exterior-releasing, damp-drying action. Damp-heat with a yellow coat, dry Yin-deficiency cough and deficient sweating are the wrong solo patterns. Hot swollen joints or high fever need medical assessment.
Why is Cang Zhu said to brighten the eyes? Is it an eye supplement?
It is traditionally used for night blindness and dim vision, often cooked with pork or sheep liver, to dry dampness, raise the clear Yang and nourish the eyes. That pattern is Spleen dampness with clear Yang failing to rise—not every drop in vision. It does not replace an eye examination. High myopia, glaucoma and retinal disease need specialist care. Do not drink Cang Zhu as a daily “eye tea.”
Which herbs is Cang Zhu combined with? What are the representative formulas?
With Magnolia bark, tangerine peel and licorice it forms Ping Wei San. With Phellodendron it is Er Miao San; adding Achyranthes and coix makes San Miao and Si Miao. With Cyperus and Chuanxiong it appears in Yue Ju Wan for constraint. Paired with Bai Zhu it both tonifies and mobilizes. Formulas should be designed by a qualified practitioner.
How do you choose and store Cang Zhu?
For Mao Cang Zhu choose firm rhizomes with a yellowish-white cut surface, many oil cavities, a strong aroma, and white needle crystals that may appear on standing. Bei Cang Zhu is less aromatic and looser. Bran-fried slices are deep yellow with a scorched fragrance. Store cool and dry, protected from rancidity and insects. Discard moldy, sour or scentless pieces. The label should state Mao or Bei Cang Zhu and raw versus bran-fried; do not confuse it with Bai Zhu.
