In this third 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/Rocky Mountain Oils (NAN/RMO).
Protective blends from different brands tend to contain essential oils of clove, cinnamon, lemon, rosemary, and eucalyptus, though some 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/Rocky Mountain Oils: Clove, Cinnamon Bark, Lemon, Lemon Eucalyptus, Ajowan Seed, Thyme, Orange, Oregano, Nutmeg, Rosemary, Red Mandarin, Ginger Root.
For the third experiment on these blends, I chose to sample water directly from two of our toilets, using a disposable pipette. The water was placed in a disposable cup and the dishes were prepped by dipping a cotton swab into the water and applying it to the surface of each plate. Insulin syringes were then used to dispense 0.010g (10mg) of each blend to the individual plates (black dots on plates show location). After incubation at 98 degrees Fahrenheit for 48 hours, I removed them from the incubator, made observations, and took measurements and photos.
Observations & Results.
Blends were grouped based on the size of the zone of inhibition around the oil, measuring the minimum distance from where the essential oil blend was placed on the petri dish, accounting for the spread of the oil, to where bacteria was found growing. Blends in Group One had a zone of inhibition that only existed where the oil itself had been placed and spread during incubation. The bacteria that grew on the plates, grew on the outside edge of the oil. The blends in Group Two had a zone of inhibition that was 0.5cm. Blends in Group Three had a zone of inhibition that was 1.0cm. The remaining dishes in Group Four had zones of inhibition that were greater than 1.0cm. Please note that, in the images, it may be difficult to see the oil, the outer edge of where the oil spread, and zone of inhibition. I've provided images at different angles to try to help make the results more evident.
Group One: Oil-only zone of inhibition.
Plant Therapy KidSafe Aura Cacia
Group Two: 0.5cm
Butterfly Express Ameo
Group Three: 1.0cm
Group Four: >1.0cm
Nature's Gift Plant Therapy
Table 1. A comparison of the essential oils in each blend.
The results of this experiment displayed a range of efficacy from a small zone of inhibition with little to no aromatic effect on bacterial growth, to a larger zone of inhibition with greater aromatic effect.
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 and Nature's Gift appear to have been the most effective in this experiment, with Native American Nutritionals/Rocky Mountain Oils (NAN/RMO) following close behind. When comparing the ingredients of these blends, again, 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. Now, for a third time, it seems likely that the constituents in cassia may be a major contributing factor to inhibiting the growth of bacteria for these blends.
NAN/RMO out-performed the rest of the blends for a second time. The reason for this may be due to the fact that NAN/RMO's blend contains several different essential oils that none of the other blends contain (see Table 1). Another interesting note is that NAN/RMO and Nature's Gift are the only two blends containing lemon eucalyptus. Therefore, it's possible that lemon eucalyptus may be partially responsible for NAN/RMO's and Nature's Gift's success in this experiment.
Although Plant Therapy KidSafe and Aura Cacia's blends had bacterial growth on the edge of where the oil was placed after 48 hrs incubation, they still continued to prevent growth where the oil was present. Therefore, these blends appear to be able to inhibit bacterial growth where the oil came into contact with the bacteria. The lack of a larger zone of inhibition demonstrates the inability of these blends to affect bacterial growth aromatically, at least after 48 hrs. 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 this type of bacteria.
Read Part Two, where it was discussed that lemon essential oil may be a factor in the success of Plant Therapy's blend.
One essential oil that may not have contributed to the success of these blends, is tea tree. Top performer, Nature's Gift, and the lesser effective blend by Aura Cacia, both contain tea tree (See Table 1.).
In conclusion, the two blends by Plant Therapy and Nature's Gift performed well in this experiment, in addition to the previous two. It's interesting to note that although the methods for this experiment were improved to make sure that the amount of each oil in each dish was consistent and precise amongst the 13 tested, that the results were similar to those in previous experiments. 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, OR when needing to clean the bathrooms... it seems that these two blends might be better choices. But ultimately, most of these blends appear to be good options, depending on your preferences.
Thanks for reading! Please let me know your thoughts on this experiment on my Essential Oil Testing Facebook page.