There are seven known coronaviruses that infect humans, including four that are responsible for about 15% of common colds. The four “cold” coronaviruses affect the upper respiratory tract and cause symptoms such as sore throat or runny nose. Three coronaviruses have caused major human disease: SARS-CoV, MERS-CoV, and SARS-CoV-2 virus, or “the novel coronavirus” as it’s commonly called. These three affect the lower respiratory tract (the lungs). It is unclear whether SARS-CoV, MERS-CoV, or SARS-CoV-2 could also affect the upper respiratory tract (Yang et al 2020).
Antiviral studies on essential oil, so far.
At the time of writing this article, there is no known cure for COVID-19 (although many possibilities are being tested), and there is currently no research into the effect essential oils may have on this particular virus. We are therefore not suggesting any treatment for SARS-CoV-2 infection with essential oils. Current standard of care for COVID-19 is supportive only (Becker S 2017).
Essential oils considered to be “antiviral” are not universal virus killers.
Before we explain the existing research on “antiviral essential oils”, it is important to clarify the difference between virucidal and antiviral. “Antiviral” means that a compound inhibits the proliferation of a virus, while “virucidal” means a virus is destroyed or deactivated. In many instances, essential oils may be effective in killing one specific virus, but not another. For example: Tea tree (Melaleuca alternifolia) essential oil inhibits the proliferation of influenza viruses inside cells (making it antiviral), but only modestly inhibits HSV-1 and HSV-2 (Garozzo et al 2009). Tea tree essential oil was not able to inhibit proliferation of the non-enveloped viruses poliovirus 1, adenovirus 2, echovirus 9, and Coxsackie B1 (Garozzo et al 2009).
Much of the existing research on antiviral essential oils is on viruses that cause skin disease (herpes simplex I and II: HSV-1 and HSV-2), which has little relevance to viruses that cause respiratory tract infections.
The closest to an applicable study is an in vitro study examining SARS-CoV (the 2002/2003 outbreak virus) and the effect of several essential oils. The authors report that a distilled oil extracted from Laurus nobilis berries was an effective virucidal against SARS-CoV (Loizzo et al 2008). The L. nobilis berries were sourced from a region in Lebanon, and the essential oil contained β-ocimene, 1,8-cineole, α-pinene, and β-pinene as the main constituents. This essential oil also contained eremanthin and dehydrocostus lactone as minor constituents at 3.65% and 7.57%, respectively (Liozzo et al 2008). These compounds are somewhat unusual in essential oils, but at least one in vitro study found that dehydrocostus lactone had activity against hepatitis B virus, an enveloped DNA virus (Chen et al 1995). However, laurel berry essential oil is not commercially available, and laurel leaf essential oil is not the same substance. It is possible that the oil used was a combination of essential oil and fatty oil made from Laurel berries by traditional methods, since only 56% of volatile compounds were identified (Tisserand and Young 2012, p322).
Research into coronaviruses may eventually address the antiviral effects of essential oils, but to date it is limited.
There are some claims that essential oils will help protect you from, or treat COVID-19, they are not based on evidence. However, this does not mean you cannot or should not make use of essential oils for respiratory and psychological support.
References:
Becker, S. (2017). “Essential oils to prevent the spread of flu” Tisserand Institute https://tisserandinstitute.org/essential-oils-flu/
Chen, H., Chou, C., Lee, S., Wang, J., Yeh, S. (1995). “Active compounds from Saussurea lappa Clarks that suppress hepatitis B virus surface antigen gene expression in human hepatoma cells” Antiviral Research 27(1-2), 99-109. https://dx.doi.org/10.1016/0166-3542(94)00083-k
Garozzo, A., Timpanaro, R., Bisignano, B., Furneri, P., Bisignano, G., Castro, A. (2009). “In vitro antiviral activity of Melaleuca alternifolia essential oil” Letters in Applied Microbiology 49(6), 806-808. https://dx.doi.org/10.1111/j.1472-765x.2009.02740.x
Loizzo, M., Saab, A., Tundis, R., Statti, G., Menichini, F., Lampronti, I., Gambari, R., Cinatl, J., Doerr, H. (2008). “Phytochemical analysis and in vitro antiviral activities of the essential oils of seven Lebanon species” Chemistry & Biodiversity 5(3), 461-470. https://dx.doi.org/10.1002/cbdv.200890045
Tisserand, R., Young, R. (2014). “Essential oil safety: A guide for health care professionals” https://dx.doi.org/10.1016/c2009-0-52351-3
Yang, Y., Peng, F., Wang, R., Guan, K., Jiang, T., Xu, G., Sun, J., Chang, C. (2020). “The deadly coronaviruses: The 2003 SARS pandemic and the 2020 novel coronavirus epidemic in China.” Journal of autoimmunity https://dx.doi.org/10.1016/j.jaut.2020.102434
