Piper retrofractum, commonly known as Javanese long pepper, is traditionally used in various Southeast Asian and Ayurvedic medicinal systems for respiratory conditions, including lung congestion. Historical texts and ethnobotanical records document its use as an expectorant and stimulant, often incorporated into herbal remedies for coughs, colds, bronchitis, and related symptoms. The primary rationale behind its use is the pungent, warming quality of its fruits, which are believed to help clear phlegm and stimulate respiratory function.

However, direct scientific studies specifically validating the efficacy of Piper retrofractum for treating lung congestion are limited. Some research on related species, such as Piper longum and Piper nigrum, suggests possible bronchodilatory, anti-inflammatory, and expectorant effects, but extrapolation to P. retrofractum is not fully supported by robust clinical evidence. Most available support for its use in lung congestion is therefore based on long-standing traditional practices rather than modern clinical trials or pharmacological studies.

In summary, while Piper retrofractum has a strong historical foundation for use in managing lung congestion, contemporary scientific validation is lacking. Its traditional use persists in some cultures, but healthcare providers should note the paucity of rigorous scientific evidence.