Prescriptions that are made up of expectorants with the action of eliminating phlegm, and applied in the treatment of various phlegm syndromes are known as prescriptions for eliminating phlegm.
 
Phlegm syndromes, in the light of the pathogenic factors, are roughly divided into damp-phlegm syndrome, heat-phlegm syndrome, dryness-phlegm syndrome, cold-phlegm syndrome and wind-phlegm syndrome. Consequently prescriptions for eliminating phlegm are also classified correspondingly into prescriptions for drying dampness and eliminating phlegm, prescriptions for clearing away heat and eliminating phlegm, prescriptions for moistening dryness and eliminating phlegm, prescriptions for warming and eliminating cold and phlegm, and prescriptions for eliminating phlegm and subduing wind.

Prescriptions for moistening dryness and eliminating phlegm are chiefly composed of drugs that moisten the lung and eliminate phlegm, which possess the actions of moistening the lung and clearing away heat, removing phlegm and relieving cough, and are fit for phlegm syndrome due to lung-dryness and deficiency of body fluid, leading to phlegm transformed from fluid by deficiency-fire.

Prescriptions for warming and eliminating cold and phlegm are mainly formed by drugs with the effect of warming the lung and reducing phlegm to stop cough and suitable for cold fluid-retention due to yang deficiency of the spleen and kidney or fluid-retention due to lung-cold. Prescriptions for eliminating phlegm and subduing wind include expectorants in combination with drugs that calm the liver and suppress pathogenic wind, which have the actions of resolving phlegm and suppressing endogenous wind. They are indicated for retention of turbid phlegm in the middle-energizer and upward disturbance of wind-phlegm due to stirring of liver-wind.
 
Phlegm is often generated from the accumulation of dampness and, because the spleen is in charge of the transportation and transformation of dampness, there goes the saying "The spleen is the source of phlegm". Phlegm is substantial pathogenic factor, and apt to disturb qi-function. Thus expectorant prescriptions often involve drugs with the action of reinforcing the spleen so as to deal with the root cause of phlegm and drugs with the action of regulating flow of qi to make the flow of qi smooth and remove phlegm. Prescriptions for drying dampness and eliminating phlegm are mostly warm and dry in nature and apt to stir blood, which should be used with caution for patients with hemoptysis.