Chinese Herbology

Medicinal Chinese herbs have been used for centuries to cure diseases and alleviate discomfort due to many different disorders. The first herbal classic written in china was published in the Qin Dynasty (221-206 BC) called the Agriculture Emperors Materia Medica. The first plants discovered and used were usually for digestive system disorders (i.e. Da Huang ) and slowly as more herbs were discovered the herbs became more useful for an increasing number of ailments and herbal tonics were created.

Every herb has its own properties which include its energy, its flavour, its movement and its related meridians to which it connects too.
The for types of energies are cold, cool, warm and hot. Usually cold or cool herbs will treat fever, thirst, sore throat and general heat diseases. Hot or warm herbs will treat cold sensation in the limbs, cold pain and general cold diseases.
The five flavours or herbs are pungent, sweet, sour, salty and bitter.
Pungent herbs are generally used to induce perspiration and promote circulation of both blood and Qi. These herbs are usually used for superficial disorders. Sweet Herbs have 3 main functions; nourishing deficiency, harmonizing other herbs or reduce toxicity, relieve pain and slow the progression of acute diseases. Sour Herbs also have 3 functions; constrict, obstruct and solidify. These herbs are good to stop perspiration, stop diarrhea, stop seminal emission and stop leucorrhea. Salty herbs soften hardness, lubricate intestines and drain downward. These herbs are used to treat hard stool with constipation or hard swellings as in diseases like goitre. Bitter herbs induce bowel movements, reduce fevers and hot sensations, re direct rebellious Qi, dry dampness and clear heat. They can also nourish the kidneys and are used to treat damp diseases.
After a herb is absorbed by a patient it can move in 4 different directions; upward towards the head, downward towards the lower extremities, inward toward the zang-fu organs or outward towards the superficial regions of the body. Upward movement herbs are used for falling symptoms like prolapsed organs. Downward moving herbs are used to push down up surging symptoms like coughing and vomiting. Outward moving herbs are used to induce perspiration and treat superficial symptoms that are moving towards the interior of the body. Inward movement of herbs induce bowel movements and promote digestion.
Each herb will have a corresponding meridian or meridians to which it will correspond to. For example; Jie Geng corresponds to the lungs and can be used for asthma or cough. Rib pain and sore eyes relate to the liver so as Gou Teng has an affinity for the liver meridian it can be used for the treatment of liver diseases.

http://tcm.health-info.org/Herbology.Materia.Medica/HerbsWebPage.htm