Can Essential Oils Improve Indoor Air Quality?

Many people are running indoor essential oil diffusers, claiming it cleans their home’s air.  Does this really work?  Can essential oils improve indoor air quality?

By Kathy Sadowski, MS in Aromatherapy, Registered Aromatherapist, LMT

There are many airborne contaminants floating around our indoor air that cause illness.  Viruses, fungi, bacteria, and toxic particulates make our air less then fresh.  In recent years, many people have turned to essential oil diffusers because they believe it kills the pathogenic microbes found in indoor air.  The problem with this idea is that the 1000’s of studies demonstrating antimicrobial actions of essential oils are not airborne measurements.  Identifying an essential oil’s in vitro actions or topical antimicrobial activities does not translate to how effective it will be against microbes in the air.

Fortunately, in the past few years, researchers have begun to create lab environments to test the antimicrobial actions of essential oils in the air.  Certain essential oils have shown promise against airborne pathogens.  Research has only just begun in this field, and it is also important to figure out the safe dosage amount for humans and pets.  In other words, research needs to answer the question: What is the correct dosage to kill microbes without harming people and pets?

Too much essential oil diffusion actually contaminates the air.  Excessive exposure to essential oils diffused in our air can lead to respiratory issues like bronchial constriction, asthma attacks, and increased mucus production.  Other health concerns are skin sensitizations, cardiac issues, neurotoxic reactions such as seizures, and psychological issues like increased symptoms of anxiety.  In extreme cases of airborne overdose, death can occur.  Sadly, very small children and pets are the most susceptible.

With essential oils, a very small amount goes a long way and experts in the aromatherapy industry share the phrase: less is more, to describe safe use of essential oils.  Each oil has a therapeutic margin, where the correct dose is healthful, but an amount exceeding the therapeutic margin can be hazardous.  For example, bergamot is considered a calming essential oil.  In a recent study of 100 spa workers in Taiwan, inhaling bergamot essential oil for one hour reduced their blood pressure.  But they were exposed to the aroma all day, and inhaling beyond one hour, actually began increasing their blood pressure, potentially having a negative effect on their cardiac health.

Which essential oils have shown to improve air quality and what is the correct dosage amount?

• Pine, clove, lavender, eucalyptus, tea tree, oregano, thyme, lemon, and anise have shown in studies to reduce microbes in the air.  More research is necessary.
• In one study, lavender, eucalyptus, and tea tree were effective ONLY in the first 30-60 minutes, but not beyond that time in reducing airborne microbes.
• Certain essential oils are not appropriate around pets and very small children such as tea tree, oregano, thyme, anise, eucalyptus, and clove.  Diffusion of essential oils is not recommended around those with asthma and certain other bronchial conditions.  Review contraindications for each essential oil before diffusing in your home.

So here is a basic guideline:

Use your diffuser sparingly, for less than one hour at a time.  Do not diffuse in a small enclosed space.  Certainly do not leave a diffuser on all day long at risk of overexposure!  In a cool mist diffuser, use about one drop of essential oil per ounce of water.  Make a blend with three to six of the following essential oils:  pine, clove, lavender, eucalyptus, tea tree, oregano, thyme, lemon, and anise.  Decrease this amount with children based on body weight.  Avoid diffusing around babies.  With pets, offer them an escape route to a room that does not have any essential oil aroma, especially with cats as they are more affected than dogs and overexposure can lead to death.

Pictured: Tea Tree Oil

Indoor Air Quality Research

• At a dilution of 2.5%, pine oil was effective against certain airborne fungi.  This can help improve indoor air quality.  From:  Motiejūnaitė, O., & Dalia Pečiulytė, D. (2004). Fungicidal properties of Pinus sylvestris L. for improvement of air quality. Medicina (Kaunas), 8, 787-794.
• Bergamot essential oil initially reduced heart rate in a spa environment.  But the 100 workers studied had increased heart rate due to over exposure beyond one hour.  From:  Chuang, K. J., Chen, H. W., Liu, I. J., Chuang, H. C., & Lin, L. Y. (2014). The effect of essential oil on heart rate and blood pressure among solus por aqua workers. European journal of preventive cardiology, 21(7), 823-828.
• In a review of studies, the author indicated clove as the most effective essential oil to improve air quality related to airborne fungi.  Tea tree, oregano, thyme and lemon essential oils also showed potential.  More research is necessary on proper concentration, best delivery method, and safe dosage amount for humans.  From:  Whiley, H., Gaskin, S., Schroder, T., & Ross, K. (2018). Antifungal properties of essential oils for improvement of indoor air quality: a review. Reviews on environmental health, 33(1), 63-76.
• Lavender, eucalyptus, and tea tree essential oils were diffused to test improved indoor air quality.  Airborne microbes were reduced only between the first 30-60 minutes of oil evaporation.  The author points out that excessive use of essential oils can cause increased secondary pollutants such as formaldeyhyde into the air.  From:  Su, H. J., Chao, C. J., Chang, H. Y., & Wu, P. C. (2007). The effects of evaporating essential oils on indoor air quality. Atmospheric Environment, 41(6), 1230-1236.
• Clove, lavender, and eucalyptus essential oils were tested against fungi found in indoor air.   Clove showed the strongest action, and all three oils were better than vinegar at reducing airborne fungi.  From:  Schroder, T., Gaskin, S., Ross, K., & Whiley, H. (2018). Antifungal activity of essential oils against fungi isolated from air. International journal of occupational and environmental health, 1-6.
• Tea tree oil was tested against two common industrial cleaners, as well as alchohol and vinegar in its action against indoor fungal contamination.  Tea tree was strongest of the five agents evaluated.  From:  Rogawansamy, S., Gaskin, S., Taylor, M., & Pisaniello, D. (2015). An evaluation of antifungal agents for the treatment of fungal contamination in indoor air environments. International journal of environmental research and public health, 12(6), 6319-6332.
• A eucalyptus species demonstrated airborne antituberculosis actions.  From:  Ramos Alvarenga, R. F., Wan, B., Inui, T., Franzblau, S. G., Pauli, G. F., & Jaki, B. U. (2014). Airborne antituberculosis activity of Eucalyptus citriodora essential oil. Journal of natural products, 77(3), 603-610.
• Tea tree and anise essential oil were effective in removing airborne fungi that cause bio-deteriorization of old manuscripts in a museum.  Further research is necessary to determine toxicity and effectiveness.  From:  Sahab Ahmed, F., Sidkey Nagwa, M., Abed Nermine, N., & Mounir, A. (2014). Studies on indoor air quality in the repositories of the national library and archives of Egypt. Int J Sci Res, 3(11), 2122-2128.
• Excessive exposure to aromas can have negative health effects.  From:  Wolkoff, P., & Nielsen, G. D. (2017). Effects by inhalation of abundant fragrances in indoor air–An overview. Environment international, 101, 96-107.