The unique design of Fengsui Dan was first recorded in the 13th century pharmacological encyclopedia, Prescriptions from the Imperial Apothecary (Yuyaoyuan fang). The popularity of the remedy in certain contemporary herbal circles, however, is mostly due to the influence of the Qing dynasty scholar-physician Zheng Qin’an, who featured Fengsui Dan prominently in his treatise True Transmission of the Fundamental Principles of Medicine (Yili zhenchuan). Since the late 19th century, the formula has thus become known as one of the core remedies of the Sichuan Fire Spirit School of Chinese Herbal Medicine (Huoshen Pai) that traces its lineage back to Zheng—a medical philosopher who emphasized the pivotal importance of the body’s yang qi. Along with Qianyang Dan (Submerge the Yang Pellet), another landmark remedy recorded in the same work, this formula focuses primarily on restoring the downward momentum of physiological yang qi. But rather than utilizing the down-drawing capacity of the hot and pungent root aconite, the design of Fengsui Dan features large amounts of the cold and bitter bark phellodendron bark. The unusually prominent role of phellodendron bark in this formula stems from its Daoist reputation of containing the essence of the “Three Functional Realms” (sancai), namely Heaven, Earth and Humanity and the associated therapeutic effect on all three burning spaces of the body—by virtue of having a natural affinity to the Heart via its bitter flavor, to the Kidney via its cold temperature, and to the Spleen via its yellow color. The remedy, moreover, uniquely highlights phellodendron bark's sub-function of “firming up the Kidney and consolidating essence”. By pairing this herb with the distinctly downward momentum of a rare variety of wild-crafted cardamon (Xi Sharen, Amomum villosum), Fengsui Dan can be used as a base formula for a wide range of pathologies caused by “disconnection of Fire and Water”. While Zheng Qin’an himself described the clinical indications for this formula in very similar fashion to those of Qianyang Dan, it should be noted that the ingredients in Fengsui Dan are distinctly cooler in nature. Appropriate prescription of this formula, therefore, requires obvious signs of false heat in the upper part of the body. The typical Qianyang Dan patient, in contrast, exhibits more cold and yang deficiency symptoms in the lower part of the body. In order to avoid confusion and harness the unique benefits of both approaches, the Yunnan branch of the Fire Spirit School often combines both remedies in the form of Qianyang Fengsui Dan (Submerge Yang and Consolidate Essence Pellet).