Rhizome of Gaint Knotweed Classic Formulas … Natural Herb Library

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Invigorates blood and dispels stasis ... Hu Zhang is used for traumatic injury, amenorrhea, fixed pain, and mass-like stasis patterns.
Clears heat and resolves toxicity ... traditional use extends to damp-heat jaundice, hot sores, and inflammatory lesions.
Transforms phlegm and stops cough ... it is chosen when Lung heat and thick phlegm produce productive cough or wheezing.
Unblocks the bowels and drains dampness ... older use includes constipation and damp-heat obstruction when heat and stasis bind together.

Trauma and blood-stasis combinations with Ru Xiang, Mo Yao, or Yan Hu Suo ... common strategy for bruising and fixed pain.
Damp-heat and jaundice pairings with Yin Chen or Zhi Zi ... classical logic when heat and dampness lodge in the Liver-Gallbladder system.
Cough and phlegm combinations ... Hu Zhang can be added when productive cough carries an inflammatory heat component.

Traditional materia medica describes Hu Zhang as bitter and slightly cold, entering the Liver, Gallbladder, and Lung to move blood, clear heat, transform phlegm, and stop cough.
Its blood-moving and heat-clearing combination helps explain why the herb bridges traumatology, hepatitis-jaundice, and productive-cough use.