Cineole, also known as eucalyptol, is a natural organic compound found in eucalyptus oil and several other plant essential oils. Its use for respiratory congestion is supported by scientific evidence. Multiple clinical studies and reviews have investigated cineole’s effects on airway diseases, particularly in conditions like bronchitis, sinusitis, and chronic obstructive pulmonary disease (COPD).

Cineole acts as a mucolytic (helping to thin and loosen mucus) and has anti-inflammatory, bronchodilatory, and mild antimicrobial properties. Randomized controlled trials have demonstrated that oral cineole supplementation can reduce the severity and frequency of coughing fits, improve airflow, and decrease mucus production in patients with acute or chronic bronchitis. For example, a 2012 Cochrane Review and several placebo-controlled studies found cineole significantly improved symptoms of congestion and mucous hypersecretion compared to placebo. Its mechanism involves inhibition of cytokines and reduction of airway inflammation, as well as direct effects on mucus viscosity.

These findings have led to its use in over-the-counter remedies and prescription formulations for upper and lower respiratory tract conditions. However, while the evidence is robust for mild to moderate congestion, especially in adults, more research is needed for pediatric use and long-term safety. Overall, cineole’s use for supporting congestion is evidence-based and recognized in clinical practice guidelines in several countries.