The traditional uses of plant remedies and the known pharmacological activity of plant constituents often coincide. However, herbal medicine is very distinct from medicine based on western pharmaceutical drugs.
Herbal medicine is plants, and plants are food. Natural foods are better at maintaining health, and additives such as preservatives and other synthetics can have negative effects on the body. Herbal formulas are like a natural food diet specifically designed to treat your specific health issues. You've heard the saying "nature provides"? It very much applies in this case.
Herbal formulas contain herbs to balance each other, to synergistically increase efficacy and enhance safety. Herbs with opposing properties are combined to control each other. Or, two similar herbs combined may strengthen their action.
Your herbal formula is designed for your individual constitution in order to correct the source of internal imbalance. Everyone is different, and no single disease presents the same from person to person. Herbal medicine is practiced with this in mind.
Are herbs safe?
Chinese herbal medicines are very safe when prescribed correctly by a properly trained practitioner. Allergic type reactions are rare, and will cause no lasting damage if treatment is stopped if symptoms appear.
My training includes study in western pharmaceuticals, and their potential interactions with certain herbs. As long as I am informed on what western drugs you are taking, the possibility of a negative reaction is very low.