What is the difference between raw rehmannia and prepared rehmannia?

Rehmannia root and prepared rehmannia root usually refer to the two traditional Chinese medicinal materials Rehmannia Root (Sheng Di Huang) and Prepared Rehmannia Root (Shu Di Huang). Under normal circumstances, there are certain differences between Rehmannia Root and Prepared Rehmannia Root in terms of properties, taste, channels entered, functions and indications, prescription application, origin and processing, and precautions for use. Medication should be used under the guidance of a physician. Detailed analysis is as follows:

1. Properties, Taste, and Channels Entered

Rehmannia Root has a sweet and bitter taste and is cold in nature, primarily entering the Heart, Liver, and Kidney channels; whereas Prepared Rehmannia Root has a sweet taste and is slightly warm in nature, primarily entering the Kidney and Liver channels. Overall, there is a clear difference in their natures, and Rehmannia Root affects a broader range of channels.

2. Functions and Indications

Rehmannia Root is mainly used to clear heat and cool the blood, nourish yin and promote body fluid production, and also has a hemostatic effect. It can be used to treat various bleeding symptoms caused by blood heat. Prepared Rehmannia Root mainly functions to nourish the blood, enrich the kidneys, and support yin. It is commonly used to treat symptoms such as dizziness, palpitations, and insomnia.

3. Prescription Application

In prescription formulation, Rehmannia Root is primarily used to treat warm-heat diseases and can be combined with herbs such as Tree Peony Bark (Mu Dan Pi) and Scrophularia Root (Xuan Shen). Prepared Rehmannia Root is effective in regulating and nourishing the blood and is often used together with Cornus Fruit (Shan Zhu Yu), Chinese Yam (Shan Yao), and similar herbs.

4. Origin and Processing

Rehmannia Root is a natural herbal medicine primarily derived from the root of Rehmannia glutinosa, a plant species in the genus Rehmannia. It consists of the fresh or dried tuberous roots and is unprocessed. Prepared Rehmannia Root is processed Rehmannia Root, typically manufactured through processes such as steaming and drying.

5. Precautions for Use

Rehmannia Root has a greasy and moist nature, which may more easily impair the spleen yang and hinder stomach qi. Patients with indigestion or spleen-stomach deficiency should use it cautiously to avoid side effects such as abdominal discomfort, loss of appetite, reduced food intake, and loose stools. Prepared Rehmannia Root has a relatively milder nature but should be used cautiously in individuals with phlegm-dampness in the body to avoid exacerbating the condition.

There are clear differences between Rehmannia Root and Prepared Rehmannia Root in multiple aspects. Therefore, selection should be based on individual conditions and disease characteristics when using them.