I have been asked many times about whether putting drops of essential oils on masks is a good idea.
Generally, I do not recommend putting any essential oils on your mask unless you will only be inhaling for a few minutes, then changing the mask, taking it off or discarding if it is disposable. If it is a reusable mask you will want to thoroughly wash it between uses.
Essential oils are concentrated chemical compounds representing a significant amount of plant material. Constant and deep inhalation of even one drop of most essential oils that close to your nose and eyes can be very intense. Potent oils such as peppermint, rosemary or eucalyptus can have a detrimental effect with too much exposure.
Most essential work in the first few minutes of inhaling and then should be stopped, whether applied to a mask, vaporizer, or other direct inhalation. Adverse effects on the lungs especially with asthma or chronic bronchitis are possible as these conditions can be aggravated by any strong aroma, natural or not.
The eyes can be affected as vapor from the essential oil can cause irritation or redness leading to blurry or watery eyes. The effects on the eyes are more pronounced if wearing glasses as the vapor expelled tends to go right up between the eyes and glasses, trapping airborne oil molecules which settle in the eye. Anyone who wears glasses probably knows this anyways.
If you still feel compelled to use essential oils on your mask, please do it sparingly or make a spray which will have a gentler effect.