In Traditional Chinese Medicine (TCM), Phlegm is one of the pathogenic (disease causing) factors responsible for the occurrence and development of a range of disorders. Phlegm is considered as a product from disharmony of body fluids that can produce either external, visible phlegm, such as sputum secreted by the respiratory tract, or internal, invisible phlegm.
The external phlegm (substantial phlegm) phlegm is generally regarded as the visible substance secreted by the Lungs and upper respiratory tract which can be either coughed or spat out, or vomited up.
Internal, invisible phlegm is considered a particular larger problem in TCM. It is usually the consequence of internal disruption of the body’s fluid metabolism, either through qi stasis, yang qi deficiency or similar reasons. In translation, the internal phlegm is often formed by dysfunction of the lungs and the spleen and triggerd by fire (heat) which consumes body fluids.