Polygala (most commonly Polygala tenuifolia or Polygala senega) has a long history of traditional use as a remedy for cough and other respiratory ailments in both Chinese and North American indigenous medicine. In Traditional Chinese Medicine (TCM), Polygala (known as Yuǎn Zhì) is used to "transform phlegm" and "open the orifices," and is often included in herbal formulations for cough, bronchitis, and other phlegm-related respiratory disorders. Similarly, North American indigenous peoples traditionally used Polygala senega (Senega root) as an expectorant to help clear mucus from the lungs.

The evidence base from modern clinical research is limited. Preclinical studies and some animal experiments suggest that extracts of Polygala species may have expectorant, antitussive (cough-suppressing), and anti-inflammatory effects, possibly mediated through modulation of airway secretions and mild central nervous system activity. However, there are few well-designed human clinical trials to confirm these effects, and the quality of available studies is generally low.

In summary, the use of Polygala for cough is primarily justified by a strong tradition in herbal medicine, with some supportive but inconclusive preclinical evidence. Its use is not yet validated by high-quality clinical research.