Effects of essential oils on symptoms and course (duration and severity) of viral respiratory infections in humans: A rapid review

Oral doses of certain essential oils may reduce symptoms of acute respiratory infections of viral origin. It is likely that the commercially available essential oil capsules Myrtol® (a mixture of essential oils of eucalyptus Eucalyptus globulus, sweet orange Citrus sinensis, myrtle Myrtus communis and lemon Citrus limonum) and Tavipec® (spike lavender Lavandula latifolia) could also provide mild to moderate symptom relief in patients with viral respiratory diseases. Myrtol® may also improve the course (duration and severity) of acute bronchitis of viral origin, in humans. Both products were well tolerated, with most of the mild to moderate side-effects affecting the gastrointestinal tract. This review found no research evidence describing the clinical effect of inhalation of essential oils for acute respiratory viral infections. Clinical evidence from published clinical trials identified in this rapid review suggests that oral administration of blends of certain essential oils (EO) can reduce symptoms of acute respiratory infections of viral origin in humans, namely acute sinusitis and acute bronchitis. There is clinical evidence for orally administered Lavandula latifolia essential oil (Tavipec®) (n = 2) and a blend of essential oils of Eucalyptus globulus, Citrus sinensis, Myrtus communis and lemon Citrus limonum (Myrtol® and its successors GeloMyrtol® and GeloMyrtol®Forte) (n = 3) to reduce symptoms of acute sinusitis and acute bronchitis of viral origin(s) [1–5]. All five clinical trials relied mostly on (subjective) symptom scores to determine the treatment effect. Differences between treatment and placebo symptom scores in these clinical trials were statistically significant, although the differences in absolute numbers were small. Furthermore, clinical evidence suggests that Myrtol® is also able to improve the course (duration and severity) of acute bronchitis of viral origin, in humans [3,5]. No clinical evidence was found on whether EO can also improve symptoms and/or course of other acute respiratory infections, like influenza or acute respiratory distress syndrome caused by viruses of the coronavirus class. Further clinical trials with these and other EO (or blends of EO), and other administration forms, like steam inhalation or personal inhalers, are warranted to further elucidate the potential of commonly available EOs in treating acute respiratory infections of viral origin, especially influenza and COVID-19.