Please read the "About Me" section prior to reading. These home-grown experiments are a far cry from what a microbiologist would do in a lab.
In this second experiment on protective blends, I tested thirteen different essential oil blends which are marketed as being effective against bacteria, viruses, and fungi. I tested each for their ability to inhibit the growth of bacteria in an in vitro bacteriological test using petri dishes. My intentions for this experiment are (1) to determine if these blends actually inhibit the growth of bacteria as claimed, (2) to see which brands are most or least effective and to compare efficacy, and (3) to see what can be learned about which essential oils in the blends tested may contribute to increased efficacy against bacterial growth.
Nature's Gift, Butterfly Express, Edens Garden, Veriditas Botanicals, Ameo, Young Living, Plant Therapy, Plant Therapy KidSafe, Aura Cacia, doTERRA, Healing Solutions, Fabulous Frannie, and Native American Nutritionals (NAN/RMO).
This experiment is different from the previous lemongrass experiments due to the fact that each brand has their own immune defense formula and contains several different essential oils. While most brands tested contain essential oils of clove, cinnamon, lemon, rosemary, and eucalyptus, some brands have chosen to depart from this formula.
Nature's Gift: Lemon Myrtle, Tea Tree, Cinnamon Bark, Cassia, Cedarwood, Pine, Lemon Eucalyptus, Ravensara, Lemon Tea Tree, Clove.
Butterfly Express: Cinnamon Bark, Clove, Eucalyptus globulus, Lemon, Lemon Myrtle, Oregano, Oregano Wild, Rosemary, Thyme.
Edens Garden: Clove, Cinnamon Leaf, Rosemary, Lemon, Eucalyptus.
Veriditas Botanicals: Cinnamon Bark, Clove, Lemon, Eucalptus radiata, Rosemary Cineol.
Ameo: Clove, Cinnamon Bark, Lemongrass, Orange, Lemon, Rosemary, Eucalyptus radiata.
Young Living: Clove, Lemon, Cinnamon Bark, Eucalyptus radiata, Rosemary.
Plant Therapy: Lemon, Clove, Eucalyptus, Cinnamon Cassia, Rosemary.
Plant Therapy KidSafe: Spruce, Marjoram, Lavender, Rosalina, Lemon.
Aura Cacia: Sweet Orange, Lavender, Lemon, Red Thyme, Tea Tree, Eucalyptus globulus, Rosemary.
doTERRA: Wild Orange, Clove, Cinnamon Bark, Eucalyptus, Rosemary.
Healing Solutions: Cinnamon, Clove, Eucalyptus, Lemon, Rosemary.
Fabulous Frannie: Clove, Lemon, Rosemary, Cinnamon, Eucalyptus.
Native American Nutritionals: Clove, Cinnamon Bark, Lemon, Lemon Eucalyptus, Ajowan Seed, Thyme, Orange, Oregano, Nutmeg, Rosemary, Red Mandarin, Ginger Root.
To switch things up a bit, I purchased organic free range chicken breast from a local grocery store. I took about an inch cube of the chicken breast, with juices, and placed it in a plastic ziplock bag and left it on the counter, slightly open, for two days. After two days (the smell was just so pleasant), I poured the juices into a clean glass jar, added filtered water and swirled to mix. I used this solution to swab the dishes before plating the essential oil blends. After placing one drop of each blend per plate, I incubated the dishes at 98 degrees Fahrenheit for 24 hours. After 24 hours I removed them from the incubator, made observations, and took photos.
Observations & Results.
Blends were grouped based on the size of the zone of inhibition around the oil, measuring the average distance from where the essential oil blend was placed on the petri dish, accounting for the spread of the oil. Blends in Group One had no zone of inhibition. The bacteria that grew on the plates, grew where the oil was placed. The blends in Group Two had a zone of inhibition that was less than 0.5cm. Blends in Group Three had a zone of inhibition that was equal to 0.5cm. The remaining dishes in Group Four had zones of inhibition that were greater than 0.5cm. Please note that, in the images, it is difficult to see the oil and zone of inhibition. I've provided images at different angles to try to help make the results more evident.
Group One: No zone of inhibition.
Group Two: <0.5cm
Group Three: 0.5cm
Group Four: >0.5cm
Table 1. A comparison of the essential oils in each blend.
The results of this experiment are pretty straightforward. Bacterial growth was uniform across all petri dishes. Aromatic activity only locally affected bacteria and did not seem to affect the spatial distribution of growth throughout the dishes. Therefore, the size of the zone of inhibition was the quality to measure in order to assess the performance of each blend.
Unfortunately, some of the images captured cannot accurately demonstrate the true results that can be observed in person, though effort was made to provide extra images. Hopefully those that have been presented are enough for most readers to be able to see the results for themselves.
Plant Therapy's blend, "Germ Fighter" appears to have been the most effective blend in this experiment. Native American Nutritionals (NAN) and Nature's Gift fall in second and third. When comparing the ingredients of these blends, it appears that there are some explanations for why they were the top three performers.
As was discussed in Part One of the Protective Blends experiment, Plant Therapy and Nature's Gift are the only two blends containing cassia. For a second time, it seems probable that the constituents in cassia may be a major contributing factor to inhibiting the growth of bacteria by these blends.
Considering the ranking of NAN's oils in previous experiments, it was unexpected to find that it out-performed all of the blends besides Plant Therapy. The reason for this may be due to the fact that NAN's blend contains several different essential oils that none of the other blends contain (see Table 1). Another interesting note is that NAN and Nature's Gift are the only two blends containing lemon eucalyptus. Therefore, it's possible that lemon eucalyptus is partially responsible for NAN's and Nature's Gift's success in this experiment.
In addressing the two blends, Plant Therapy KidSafe and Aura Cacia, though bacteria grew where the oils were placed (after 24 hrs incubation), it appears that the oils did inhibit bacterial growth for an undetermined amount of time prior to this. The one essential oil these two blends have in common is lavender, therefore it may be reasonable to conclude that lavender essential oil is not very effective against bacteria that grows on raw chicken breast.
One remaining consideration for why one particular blend may or may not be effective at inhibiting bacterial growth, is the amount of each essential oil in each blend. For example, most of these protective blends contain lemon, but the amount of lemon essential oil in each blend may vary to a large degree. The only indication we have of the amount is in considering the order of ingredients listed on each product (see the "Formulations" section above). For the winner, Plant Therapy, the first ingredient listed is lemon essential oil. None of the other blends list lemon first, so it's possible that there is significantly more lemon essential oil in Plant Therapy's blend than in any of the other blends tested. It is known through scientific studies that antibacterial strength of any substance is impacted by its concentration. For example, the minimum inhibitory concentration (MIC) is one metric that scientists use to determine how effective a substance or chemical compound is against inhibiting bacterial growth. In this study, scientists determined the minimum concentration necessary to inhibit bacterial growth for various essential oils and strains of bacteria. In light of this, an additional hypothesis for why Plant Therapy performed best is that the amount of lemon essential oil in its Germ Fighter blend was above the MIC for the strain of bacteria tested, while the other blends had concentrations of lemon essential oil that were below the MIC.
In conclusion, the two blends by Plant Therapy and Nature's Gift performed well in this experiment in addition to the previous one. When deciding which brand or blend to purchase in order to prevent bacterial growth - whether it's bacteria that happens to spread from someone touching their nose and subsequently touching surfaces or objects in your home, or from preparing raw chicken breast on your kitchen counter - it seems that these two blends would likely be good choices.
Thanks for reading! Please let me know your thoughts on this experiment on my Essential Oil Testing Facebook page.