Cineole (also known as eucalyptol) is a naturally occurring monoterpene found in eucalyptus oil and other plant essential oils. Its use in supporting respiratory conditions, including influenza, has been explored both in traditional medicine and scientific research, though the level of evidence specifically for influenza is limited and primarily indirect. Several studies have demonstrated cineole's mucolytic, anti-inflammatory, and bronchodilatory effects, which can help alleviate respiratory symptoms such as congestion and cough that are commonly associated with influenza infections (Juergens et al., 2010). In vitro and animal studies also suggest that cineole has some antiviral properties, though direct clinical trials on its efficacy against influenza viruses in humans are lacking.

The European Medicines Agency recognizes cineole-containing preparations as traditional herbal medicinal products for the relief of symptoms in common cold and other respiratory tract diseases. However, most clinical evidence focuses on chronic respiratory diseases like asthma and chronic obstructive pulmonary disease (COPD), rather than acute viral infections such as influenza. Overall, while there is some scientific validation for using cineole to support respiratory health and symptom management, robust evidence specifically for treating influenza is limited, and it should not be considered a substitute for established antiviral therapies.