Lung disease mainly reflects dysfunctions of the lung and its functions in governing qi and breath as well as in regulating water passage. The usual clinical symptoms include cough, asthmatic breath, expectoration, stuffy nose, nasal discharge and edema.
 
Lung disease is either asthenic or sthenic. Asthenic lung disease is usually caused by prolonged disease with cough, or insufficiency of qi and yin production, or consumption of qi and yin in febrile disease that leads to asthenia of pulmonary qi and asthenia of pulmonary yin. Sthenic lung disease is usually due to invasion of pathogenic wind, cold, dryness and heat, or internal exuberance of phlegmatic dampness that leads to failure of pulmonary qi to disperse and descend, resulting in such syndromes like invasion of the lung by wind cold, invasion of the lung by dryness, invasion of the lung by wind heat, exuberance of pulmonary heat, accumulation of phlegmatic heat in the lung, retention of phlegm and fluid in the lung and mixture of wind and fluid.