Which herbs are common to Xiao Cheng Qi Tang and Hou Po San Wu Tang?

• A. Hou Po, Zhi Shi, Da Huang
• B. Hou Po, Zhi Shi, Da Huang
• C. Da Huang, Bai Shao, Zhi Shi
• D. Hou Po, Da Huang, Bai Zhu

Answer: (B)

The key idea is identifying herbs that serve the same role in both formulas: moving qi and clearing stagnation in the abdomen. The herbs shared by both Xiao Cheng Qi Tang and Hou Po San Wu Tang are Hou Po, Zhi Shi, and Da Huang. Da Huang provides a strong purgative action to purge heat and stagnation in the intestines; Zhi Shi helps regulate and move qi, break up clumps, and ensure the purge progresses smoothly; Hou Po moves qi and dries dampness, reducing abdominal fullness and supporting the downward movement of qi. Together, this trio addresses the core pattern of abdominal fullness and stagnation that both formulas target. Other herbs listed in the options are not present in both formulas, so they don’t count as common ingredients.