Thus, the tendency of the humor to continue in the direction of further imbalance is opposed. The strength and acuteness of the illness may be such that no single herb is sufficient against it. The herbs are compounded so that the ingredients have a synergistic action and effect. Sometimes there is a variance between the action of the single herb and the nature of the disease, as when a single herb works in opposite actions at the same time, like ripening chest phlegm and hindering the growth of tumors. One would compound in order to avoid aggravating one or the other of these conditions, since the desire is to treat them in sequence, not at the same time.
Some herbs have such strength that they have toxic or poisonous side effects themselves.
In such cases, a compound is devised that annuls the toxic effects. The affected organ may be far from the site of administration, and herbs are added into the compound that speed the herb to the site of action. The strength and importance of the diseased organ must be taken together. Usually an herb to dissolve a tumor is compounded with one to ease the symptoms. Distasteful herbs are compounded with those that improve their flavor.