What it is:
This herb is the root tuber of Rehmannia glutinosa Libosch. (family Scrophulariaceae) , produced mainly in the provinces of Henan and Hebei, harvested in spring and autumn, washed to remove earth, dried, sliced, used fresh or unprepared.

Property:
Sweet and bitter in flavour, cold in property, acting on the heart, liver and kidney channels.

Effects:
Removing heat from the blood and nourishing yin to promote the production of body fluid.

Used for:
1. Epidemic febrile diseases with pathogenic heat in the yin and blood systems manifested as fever, dryness in the mouth, red or deep red tongue. It is often used with rhinoceros horn and scrophularia root, as in Decoction for Clearing Away Heat in the Ying System (Qingying Tang).

2. Bleeding due to invasion of the blood by pathogenic heat, such as hema- temesis, epistaxis, hematuria, metrorr- hagia and metrosta- xis. It is often used with biota tops, lotus leaf and argyi leaf, named Bolus of Four Fresh herbs (Sisheng Wan). If the noxious heat is exu- berant with purple or black maculas and eruptions, it can be used with rhinoceros horn and moutan bark, as in Decoction of Rhinoceros Horn and Rehmannia (Xijiao Dihuang Tang).

3. Febrile diseases in the later stage with lingering low- gade fever, or chronic diseases with fever due to deffi- ciency of yin. It is used with sweet wormwood, turtle shell and anemarrhena rhizome, as in Sweet Wormwood and Turtle Shell Decoction (Qinghao Biejia Tang).

4. Syndromes of impairment of yin in febrile diseases or diabetes due to yin deficiency. For im- pairment of yin in febrile diseases marked by thirst and dryness of the mouth, red tongue and dry lips, it is often used with ophiopogon root and glehnia root, as in Stomach- nourishing Decoction (YiweiTang). For impairment of yin due to exuberant heat and deficiency of body fluid with constipation, it is used with scrophu- laria root and op- hiopogon root, named Fluid-increasing Decoction (Zengye Tang). For diabetes marked by thirst and polydipsia, it is often used with pueraria root and trichosanthes root, as in Jade Spring Powder (YuquanSan).

Dosage and administration: 10- 30g decocted in water for an oral dose.

Precautions:
This herb is sweet, cold and can cause stagnation, so in cases of deficiency of the spleen with damp pathogen marked by abdominal disten- sion and loose stool, it should not be used.