In this experiment, I tested thirteen different essential oil blends which are marketed as being protective 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.
For methods, please check the "About Me" section.
Observations & Results.
In a layout arbitrarily chosen by myself in an attempt to order them from least effective to most effective based on initial observations, here are the results after 48 hours incubation:
Below, blends were grouped based on the size of the zone of inhibition around the oil (measuring the radius from where the essential oil blend was placed on the petri dish). Blends in Group One had a zone of inhibition that was less than 0.5cm. Blends in Group Two had a zone of inhibition that was equal to 0.5cm. Group Three blends had a much larger zone of inhibition, greater than 0.5cm:
Table 1. Scores assigned to groups based on the size of the zone of inhibition.
Below is a larger image of Aura Cacia's "Medieval Mix". This blend, as well as Plant Therapy's KidSafe blend, had a zone of inhibition that did not extend beyond the spread of the oil in the dish (less than 0.5cm).
Below: Plant Therapy KidSafe blend, "Germ Destroyer". The spread of the oil is visible in this image, and bacterial growth occurred just beyond the outer edge of the oil.
Blends were then grouped according to the spatial distribution of bacterial growth. Blends in Group One were defined as having uniform bacterial growth beyond the zone of inhibition. Blends in Group Two had high density spatial distribution. Group Three - medium density. Group Four - low density. And Group Five - sparse.
Table 2. Scores assigned to groups based on the spatial distribution of bacterial growth.
Another distinguishing characteristic between the plates was the amount of large colonies that grew. The image below displays how they were grouped. Group One was defined as having over three large colonies. Blends in Group Two grew 2-3 large colonies. Group Three - one large colony. Group Four - no large colonies.
Table 3. Scores assigned to groups based on the amount of large colonies present in each dish.
One last quality that was considered was the total amount of bacterial growth that occurred in each dish. An image for this was not taken. Scores were assigned as below:
Table 4. Assigned scores for number or amount of colonies/bacterial growth.
The table below displays the assigned scores for each blend according to each distinguishing characteristic observed or measured. Qualities determined to be less effective were given larger marks against efficacy, and therefore higher scores. Scores for each blend were totaled and rank was given based on overall efficacy of the blend. Nature's Gift ranks at the top as most effective and Veriditas Botanicals ranks at the bottom as least effective.
Table 5. A comparison of the essential oils in each blend.
The results of this experiment warranted a much more complex analysis than the previous lemongrass experiments. There were several distinguishing characteristics of the type, spread, and amount of bacterial growth present in each dish. Though some brands clearly performed better than others, there were some that proved difficult to place. For example, Young Living performed well when spatial distribution and total bacterial growth were considered, but ultimately, the size of the zone of inhibition around the oil was smaller than those with higher ranking.
In an attempt to even out the scoring and weight the scores amongst the distinguishing characteristics observed and measured, scores were given from 0-7. You might notice that the zone of inhibition scores were given slightly more weight than the others. This is because I considered this measurement to be of more importance, due to the fact that the zone of inhibition is typically the standard measure used in bacteriological testing.
The justification behind factoring in the spatial distribution of the bacterial growth was to account for the aromatic activity of the blends. It appears that some blends were more effective through aromatic influence than through having a more localized zone of inhibition effect (compare Young Living or Plant Therapy's KidSafe blend which has better scores in spatial distribution, to Fabulous Frannie or Healing Solutions' Health Shield Blend). Since essential oils are valuable for their aromatic action, this is an important quality to consider.
One potential source of error in this experiment is that I only had twelve identical droppers instead of thirteen. I chose to use a different dropper for the Plant Therapy KidSafe blend since Plant Therapy was already being tested. It's doubtful that this had an effect on the experiment however, because the size of the mouth of the dropper is nearly identical to the other twelve.
Another major factor that influences the results of this experiment are that the scores and rankings are based on my observations and measurements, and are ultimately based on my personal judgment. Not everyone will agree on how to score or rank the efficacy of these blends. As an aside, it's more difficult to see clearly in the images each petri dish and the bacterial growth it contains, and therefore some images presented do not accurately reflect what can be observed in person.
Nature's Gift, Butterfly Express, and Plant Therapy are the clear winners amongst the protective blends tested. The main reason for this is likely because each of these departs somewhat from the typical Thieves-like blend. Nature's Gift contains ten different essential oils as opposed to the usual five, and it appears that the additional oils have been chosen wisely. Upon first observation, it might be suggested that Butterfly express performed well because it contains oregano essential oil, which is a known powerful antibacterial. Yet the Native American Nutritionals blend also contains oregano, as well as all of the essential oils listed in the Butterfly Express blend - except for lemon myrtle. Both Butterfly Express and Nature's Gift contain lemon myrtle, which according to the Nature's Gift website, "is a much more effective germ killer than the more familiar Tea Tree". None of the others contain lemon myrtle and therefore it's likely that this oil helped both of these blends claim top spots in the ranking order.
Plant Therapy comes in third (or tied with Young Living) even though its formulation wasn't much different than the typical protective blend. The unique difference from other 5-oil protective blends is that it contains cinnamon cassia instead of cinnamon bark. Both Nature's Gift and Plant Therapy blends contain cassia. Considering the fact that this is the one essential oil that sets Plant Therapy's blend apart from Young Living, Edens Garden, Healing Solutions, Fabulous Frannie, and Veriditas Botanicals, cassia may be the major factor involved in the success of this blend.
Ultimately, it appears that all of the blends tested were able to inhibit the growth of bacteria in the incubator for up to 48 hours. However, Aura Cacia's Medieval Mix and Plant Therapy's KidSafe blend would only be effective topically at 48 hours, but most protective blends are not advised to be used topically because of the skin irritating and sensitizing properties of certain oils. It's nice to note that the rest of the blends were still acting aromatically and inhibiting the growth of bacteria at 48 hours.
Extra Fungus/Mold Experiment.
If you've read through this post, you get to see the additional experiment I performed with these blends, on some mold I discovered growing on my organic strawberries. I almost threw them out, but then took the opportunity to put these protective blends to the test for their anti-fungal activity. The only problem was that I was one petri dish short. So there's no control to compare the blends to. Oops.
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