Horehound (Marrubium vulgare) has a long history of use in traditional herbal medicine, particularly for supporting respiratory health, including the sinuses. Historically, horehound has been used in Europe and North America as a remedy for coughs, colds, and other respiratory complaints. Its traditional application often involves herbal teas, syrups, or lozenges made from the leaves and flowering tops of the plant.

The justification for its use to support the sinuses primarily comes from its expectorant properties, as noted in herbal texts and traditional pharmacopeias. Horehound is believed to help thin mucus and promote its expulsion, which can indirectly support sinus drainage and relieve congestion. However, while there are some in vitro studies suggesting mild anti-inflammatory and antimicrobial effects, there is limited direct scientific evidence specifically validating its benefits for sinus health in humans.

Overall, the use of horehound for sinus support is mainly grounded in tradition, with anecdotal and historical usage far outweighing modern clinical validation. Most scientific research focuses on general respiratory effects, rather than targeted sinus support. As such, the evidence for horehound’s efficacy in supporting the sinuses is modest, and more robust clinical studies would be needed to confirm its traditional claims.