Piper retrofractum, commonly known as Javanese long pepper, has a long history of use in traditional medicine systems across Southeast Asia, particularly in Indonesia and Thailand. In these traditions, it is often included in herbal remedies for respiratory ailments, including bronchial congestion, coughs, and colds. The fruit is considered to have warming and stimulating properties that are believed to help loosen mucus and promote expectoration, thereby alleviating congestion. This use parallels that of its close relative, Piper longum, which is also employed for similar indications in Ayurveda and other traditions.

While preclinical studies have identified some anti-inflammatory, antimicrobial, and bronchodilatory properties in extracts of Piper retrofractum, direct evidence supporting its effectiveness specifically for bronchial congestion in humans is lacking. Most available studies are in vitro or in animal models, and the plant's traditional use for respiratory complaints remains the primary basis for its inclusion in remedies for congestion. No robust clinical trials or high-quality scientific studies have validated its efficacy for this condition. Therefore, while its use is rooted in tradition, the evidence supporting its effectiveness is modest and largely anecdotal.