Phragmites australis (common reed) has been traditionally used in various forms of herbal medicine, particularly in East Asian medical systems such as Traditional Chinese Medicine (TCM). In TCM, the rhizome of Phragmites (known as Lu Gen) is believed to have cooling and moistening properties and is commonly included in formulations for conditions characterized by "heat," such as sore throat, fever, and cough. Historical texts and traditional pharmacopeias cite its use for these indications, typically as a decoction or in combination with other herbs.

However, while there is a long-standing tradition supporting the use of Phragmites for sore throat, robust clinical or laboratory evidence validating its efficacy for this specific indication is limited. Some in vitro and animal studies suggest that extracts of Phragmites may possess anti-inflammatory or antimicrobial activities, but these studies are either preliminary or do not directly address sore throat as an outcome. There are no well-conducted clinical trials specifically investigating Phragmites rhizome for the treatment of sore throat in humans.

In summary, the use of Phragmites for sore throat is justified primarily by traditional practice rather than scientific validation, and the overall evidence supporting its efficacy is weak to moderate based on available literature.