Evidence supporting the use of: Polygala root
For the health condition: Cough (dry)

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Synopsis

Source of validity: Traditional
Rating (out of 5): 2

Polygala root (Polygala tenuifolia, also known as Yuan Zhi or "Senega root" in some contexts) has a long history of use in Traditional Chinese Medicine (TCM), where it is often included in herbal formulas to address respiratory issues, including dry coughs. In TCM theory, Polygala root is believed to "transform phlegm," "open the orifices," and "calm the spirit." For dry cough, it is typically used in combination with other herbs that moisten the lungs or resolve phlegm. Classical texts like the “Shennong Bencao Jing” and later materia medica, such as the "Bencao Gangmu," mention its use for respiratory complaints, including coughs that are dry or accompanied by scanty sputum.

Scientific studies on Polygala root for cough are limited and largely preclinical. Some animal studies suggest it may have expectorant and antitussive (cough-suppressing) effects, possibly due to its saponin and xanthone glycosides content. However, there is insufficient high-quality clinical evidence to conclusively support its efficacy for dry cough in humans. Most modern uses for cough rely on the traditional rationale and empirical use rather than robust clinical trials. In summary, Polygala root's application for dry cough is primarily justified by tradition, and the strength of the supporting evidence is modest, meriting a rating of 2 out of 5.

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