While I don’t want to compare, in any way, the seriousness of the historical impact of the plague to the relatively benign COVID-19 virus for most, I do want to point out that many people may be panicking and taking steps that could potentially WORSEN illness, rather than protect.
Essential oils have become a highly popular form of self treatment and they seem to support a sense of empowerment for individual wellness. And they can have some great applications: aromatherapy with just a drop of a favored oil can help with relaxation and/or mood, and certain oils can have strong antimicrobial effects and hormonal effects, just like using whole herbs. But each small bottle of essential oil is manufactured, most often, from vast amounts of plant material and condensed to be exponentially more potent in chemical compounds than the original botanical source.
But the current popularity has also bolstered the use of them in ways that can pose harm, particularly when they are ingested, or used in a diffuser or sprayed into the air. This can be particularly problematic for someone in the household or office who has a lung/airway disease such as asthma, or environmental allergies, or who has a tendency to get lower respiratory tract infections or sinus infections. Even short exposures can aggravate asthma and even cause flu-like symptoms in some people.
This is because they add more than just nice scents to the air, they also diffuse a wide range of VOC’s, or volatile organic compounds. Think paints, paint thinners, moth balls, pesticides; these are other common things that give off VOC’s. These chemicals can irritate the respiratory tract, affect the nervous system, and can have other effects on the body. It is preferential to limit their exposure, and use them with plenty of ventilation.
COVID-19 is forecast to very mild for most people, but it has notably more risk for those who have pre-existing lung and cardiovascular issues. Therefore it might be a good idea to reconsider their indoor use around those who are most vulnerable, especially during times of potential exposures to illness. This includes the very young and the elderly. Or, at least to weight the risk to perceived benefits. The same goes for many cleaning products (consider soap and water), smoking, synthetic fragrances, fabric softeners, candles, and spray deodorants.
For further reading on this topic:
Volatile chemicals from essential oils: Scripps UC San Diego
Harvard.edu: The effects of evaporating essential oils on indoor air quality
Volatile Organic Compounds: American Lung Association Fact Sheet