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Rehmanniae Radix Preparata (Weirui) has a mild tonifying nature and moistening properties, and can dispel wind-dampness.
It is sweet in taste and neutral in temperature. It tonifies the middle jiao and benefits qi, moistens the heart and lungs, enhances complexion, and relieves irritability and thirst.
It treats conditions caused by wind-damp toxic pathogens, such as painful eyes with ulceration (due to wind-damp), alternating chills and fever malaria (pronounced "Lian", also referring to malaria), sudden heat from wind-stroke accompanied by immobility, headache, and lower back pain (generally, persistent headaches belong to external contraction and should be treated with dispersing methods; intermittent headaches belong to internal injury and should be treated by tonifying deficiency; lateral headaches on the left are often due to wind and blood deficiency, while those on the right are often due to phlegm-heat and qi deficiency; lower back pain may also stem from kidney deficiency, qi stagnation, phlegm accumulation, blood stasis, cold-damp, or damp-heat. Cases complicated by deficiency or wind-damp are suitable for Weirui), coldness of the genitalia with spontaneous sweating, and all types of deficiency syndromes. Used as a substitute for Renshen (Ginseng Root) and Huangqi (Astragalus Root), it is neither cold nor drying, yielding remarkable effects (Wang Ang notes: Weirui is warm, moist, sweet, and neutral, a balanced herb. If prepared into pills with honey and taken in large quantities over time, it will indeed show remarkable efficacy. This is the same principle as taking Heshouwu (Polygoni Multiflori Radix) or Dihuang (Rehmanniae Radix). However, if only a few fen are added to a decoction under the assumption that it can replace Renshen and Huangqi, one is far off the mark. Generally, this herb acts slowly, and its effects are seen only after long-term use. Its primary indications are wind-damp and consumptive diseases. Therefore, Ge Xian used it for dietary therapy, Zhang Zhongjing used it to treat wind-warmth, and both Qianjin Fang and Waitai Miye occasionally employed it, never relying on it as a heavy dose. In cases of acute collapse, only Renshen and Huangqi can restore the pulse and return yang; at such times, even a jin of Weirui cannot match the effect of a few fen of Renshen or Huangqi. Contemporary physicians, citing Li Shizhen's statement that it can replace Renshen and Huangqi, indiscriminately add it to prescriptions for deficiency syndromes, gaining no benefit for the patient whatsoever! In my work *Fangjie*, I noted that ancient formulas containing Weirui for tonification are hard to find, indicating that ancients rarely used it).
It resembles Huangjing (Polygonati Rhizoma) but is slightly smaller, yellowish-white in color, and has many rootlets (the functions of these two herbs are similar, but Weirui is superior). Scrape off the skin and nodes with a bamboo knife, then soak in honey water or wine and steam before use. It is incompatible with salty brine (Tao Hongjing stated: *Shennong Bencao Jing* lists Nuwei but not Weirui, while *Bielu* lists Weirui but not Nvru. Their functions are identical, suggesting they are likely different names for the same substance).