By Sarah A. LoBisco, ND, IFMCP
Note: Part 1 of this article, published in December 2018, discusses issues of safety, essential oil quality, metabolism, and synergy when using essential oils orally. Part 2 looks at the clinical application of ingested essential oils for intestinal discomfort.
Preliminary Considerations
Before selecting a therapeutic modality of any kind, it is important to address the underlying cause and use a naturopathic and functional medicine approach to address it. I would be amiss to not briefly review some preliminary considerations for using essential oils.
For intestinal discomfort and symptoms, an integrative doctor will want to take a full history, perform a physical exam, and run the appropriate tests. Examples of laboratory assessments include imaging for detecting pathology and functional issues, assimilation and absorption markers (e.g., pancreatic elastase, products of protein breakdown, fecal fats), excess inflammatory indicators (e.g., calprotectin, eosinophil protein X (EPX), lactoferrin), a Celiac panel, SIBO breath test, markers for bacterial, viral, fungal, and parasitic overgrowth, and microbiota panels.
A “Five R” program for restoring and healing a diseased gastrointestinal tract is the preferred protocol in functional medicine, but the aspects are likely be implemented by most integrative practitioners. These Five R’s are the following:
1. Removing the cause and contributors (i.e., dietary, microbes, or environmental),
2. Replacing the nutrients that are needed for assimilation and digestion,
3. Repairing the damage to the gut,
4. Re-inoculating the good bacteria, and
5. Rebalancing lifestyle factors (sleep, stress, exercise) that can perpetuate a dysfunctional gut.(122-124)
Oral Use of Essential Oils for Intestinal Discomfort
Now, I will start the discussion on the “nuts and bolts” of internal administration of essential oils for gut discomfort. I will review the evidence in the research for the use of the most common essential oils for intestinal health and those that I personally use in my practice. I will also provide dosages, if available, that are recommended from scientific reviews and experts. Next, I will give a summary on essential oils’ antimicrobial effects and their impact on the microbiome. Finally, I will give a synopsis of how I would incorporate these essential oils in my practice.
Despite the controversary surrounding oral application of essential oils, many practitioners are already currently administrating two essential oils for gut comfort without concern. Many practitioners who run the previously mentioned lab markers have witnessed that certain essential oils are deemed “sensitive” to dysbiosis markers on various functional gastrointestinal health panels. For this reason, many functional and naturopathic medicine practitioners have experience administering the essential oils of oregano for its antimicrobial properties.124-127 and enteric coated peppermint oil for irritable bowels.128-132 Two additional essential oils I personally use in my practice are fennel and ginger. Please refer back to the previous section (Part 1) on “Internal Usage of Essential Oils: Controversy, Scare Tactics, and Bad Science” in which I highlighted the benefits of fennel oil for gut distress and its safe internal use.
There is also one proprietary blend I have found to be very clinically effective.
Peppermint Oil
Peppermint is perhaps the most researched and clinically evaluated essential oil used for intestinal discomfort. It has even been validated in several trials for its efficacy in IBS subjects.128-131
Peppermint’s mechanism of action on pain has been studied but is not conclusive. It may be related its impact on TRPM8, a transient receptor potential (TRP) cation channel. This receptor has been found to be activated by cold temperatures and menthol, a main constituent found in peppermint essential oil. It induces smooth muscle contractions inversely relational to stimulation (temperature) and initiation of Rho-kinase. This leads to smooth muscle contraction. Furthermore, there is some controversial evidence that menthol modulates intracellular calcium stores. In summary, peppermint oil may relieve intestinal discomfort through activation of TRPM, modulating calcium stores, and stimulation of menthol.129
There is a safety precaution reported in the literature that peppermint may delay gallbladder emptying. The evidence cited for this is based on one study of 12 healthy volunteers that was assessing gastrointestinal motality.128,130-131
In this experiment, the researchers compared the effects of a combination of 90 mg of peppermint oil in 50 mg of caraway oil to a proprietary formulation to two medications and a placebo that contained NaCl (salt). The participants were tested at baseline and after drinking apple juice at various time intervals. The authors simultaneously measured gastric and gall-bladder emptying ultrasonically and orocaecal transit time using the H2 breath test using lactulose.128 The authors concluded the following:
“Further investigations need to be conducted to study the effect of peppermint oil and caraway oil on a maximal contraction stimulus on the gall-bladder (e.g.after a fatty meal), to investigate the effect of a combination of both oils (as found in a number of herbal drugs) and to examine whether the pharmaco-dynamic effects can also be shown in patients suffering from motility disorders.128”
I take issue to making this safety flag for peppermint oil based on twelve healthy volunteers. Under normal conditions, fatty acids stimulate gallbladder contraction. The test drink was a non-fat juice, so how could the gallbladder be stimulated? Still, according to the Expanded Commission E, the following contraindications are reported: “Obstruction of bile ducts, gallbladder inflammation, severe liver damage. In case of gallstones, to be used only after consultation with a physician. Preparations containing peppermint oil should not be used on the face, particularly the nose, of infants and small children.”132
I believe that due to the impressive clinical trials that report the efficacy of peppermint for IBS, it may be a better conclusion that it is a modulator of digestive function rather than an inhibitor or stimulator of motility. Furthermore, with appropriate dosage, clinicians should not dismiss this essential oil for fear of harm.
Oregano Essential Oil
Whereas ingestion of peppermint oil has many clinical trials of efficacy for assisting with digestive distress, oregano oil does not. Yet, it is one of the go-to essential oils for most practitioners in treating gut discomfort related to microbial imbalances. Interestingly, clinical trials on efficacy regarding the popular use for intestinal dysbiosis is lacking.133,134 There is one lone study on inhibition of enteric parasites.125
Its isolated compound, carvacrol, was found in vivo to have protective effects against clostridium difficile associated dirrahea.135 In another in vivo model using pigs, oregano oil was found to improve intestinal permeability via modulating bacteria and immune status. Interestingly, the oregano oil used, as reported in the analysis found within the supplementary materials, did not contain the two components considered to be most active.136 Many manufactured oregano oil products are encapsulated and standardized to carvacrol and thymol.
Still, clinicians report benefits and improvements of markers of intestinal dysbiosis for their patients.
As far as safety, it is recommended to be diluted in a fatty oil due to its potentially corrosive properties.
Ginger Essential Oil
Ginger is another well-known herb for its digestive properties and alleviating discomfort. It has evidence of this from a few human trials and many in vitro and in vivo.137-142 In vitro and vivo, ginger oil has been shown to be microbe inhibiting and have inflammatory modulating properties. The constituents of ginger oil have also shown to be stomach protective,(139) possess antioxidant properties, and modulate inflammation.137-142
One study review of five trials had compelling evidence that the inhalation of a combination of peppermint oil and ginger oil could assist with nausea, though some methodical issues were reported. The authors stated, “Their results suggest that the inhaled vapor of peppermint or ginger essential oils not only reduced the incidence and severity of nausea and vomiting but also decreased antiemetic requirements and consequently improved patient satisfaction.”142
Cumin Essential Oil
Cumin essential oil is another essential oil traditionally used for digestive health. A small pilot trial with 57 subjects diagnosed with IBS using ROME II criteria assessed the efficacy of 2% cumin essential oil and had an impressive outcome. The essential oil was administered as 10 drops twice daily for four weeks. The authors concluded, “Abdominal pain, bloating, incomplete defecation, fecal urgency and presence of mucus discharge in stool were statistically significant decreased during and after treatment with Cumin extract. Stool consistency and defecation frequency were also both statistically significant improved in patients with constipation dominant pattern of IBS.”143
Proprietary Formation
I have had success using combinations of essential oils in proprietary formulations for intestinal health promotion and relief of irritation. One essential oil blend I routinely use contains the following single oils with evidence of digestive support: Artemisia dracunculus (tarragon) oil,144 Zingiber officinale (ginger) root oil,137-142 Mentha piperita (peppermint) oil,128-132 Juniperus osteosperma (juniper) oil,145 Foeniculum vulgare (fennel) oil,110-114 Cymbopogon flexuosus (lemongrass) oil,146-149 Pimpinella anisum (anise) seed oil,150 and Pogostemon cablin (patchouli) oil.
This has been very effective in my practice for relief of gastrointestinal discomfort and symptoms. Most report improvement within one month. This is likely due to the synergistic components of the essential oils.77-78
Dilution and Dosages: A Guide for Essential Oils
Now that I’ve reviewed the evidence that ingesting essential oils and that their use for intestinal discomfort is science-based, I will now discuss specific dosage guidelines. Although aromatherapists have different viewpoints on dilution amounts necessary for safe application, measurement for what constituents a single dose is a commonality.
In this section, I will provide a dosage guide compiled from the experience of experts and various merchandizers.**
Most essential oils come in 5 ml and 10 ml bottles. This equates to approximately 100 and 300 drops respectively. A general knowledge of equivalency from drops to measurements is necessary for the practitioner to understand, as most often dosage is based on drops rather than liquid measurements of essential oils. Please see Table 1 (below) for these conversions and dilutions of essential oils (EOs).117-121
What the Science Says: Internal Usage and Conversion Measurements for the Application of Essential Oils
With knowledge of which essential oils to use for abdominal pain and a tool for conversions for dosages for administration, I will now review what is in the literature for internal adminstration of these selected essential oils.
Peppermint Essential Oil
According to Examine, the dosage for peppermint essential oil “does not follow a particular dosage,”131 but is often standardized for menthol content. Quality and standards are once again validated as imperative for efficacy by this review. The authors summarize the research on this oil’s administration as follows:
“Oral supplementation of peppermint oil for the purpose of gastrointestinal health and motility involves consuming anywhere between 450-750 mg of the oil daily in 2-3 divided doses, and this is around 0.1-0.2 mL of the oil itself per dosage. The exact optimal dosage of peppermint is not known, and the numbers reflect menthol content somewhere between 33-50%.*
Usage of peppermint for the treatment of headaches involves having a solution of 10% peppermint oil and applying a relatively thin layer to the front of your head upon the start of a headache, with another application after 15 minutes and 30 minutes (for three applications in total).
Usage of peppermint for aromatherapy does not follow any particular dosing, and similar to other forms of aromatherapy it should be used as either an oil or in a distiller until a pleasant aroma permeates the vicinity.
Any form of peppermint oil should be effective although for persons who experience heartburn (acid reflux) and wish to supplement with peppermint oil for their intestines, then an enteric coated capsule would be useful (since the muscle relaxing effects may affect the esophagus if the capsule breaks prematurely).131”
The American Botanical Council’s Expanded German E Commission on peppermint further validates this reported dosage and administration.132 It states:
“Unless otherwise prescribed: 6–12 drops per day essential oil and Galenical preparations for internal and external application.
Internal:
Essential oil: Average single dose 0.2 ml.
Essential oil enterically coated form: Average daily dose 0.6 ml (for IBS).
Inhalant: Add 3–4 drops of essential oil to hot water; deeply inhale the steam vapor.
External:
Essential oil: Some drops rubbed in the affected skin areas (may be diluted with lukewarm water or vegetable oil).
Liniment: Oily preparation containing 5–20% essential oil in base of paraffin or vegetable oil applied locally by friction method.
Ointment or unguent: Semi-solid preparation containing 5–20% essential oil in base of petroleum jelly or lanolin spread on linen for local application.
Nasal ointment: Semi-solid preparation containing 1–5% essential oil.
Tincture: Aqueous-alcoholic preparation containing 5–10% essential oil for local application.”
The German E Commission has more specific quality and internal standards for essential oils than found in the United States. It reports on the constituents and their percentages that must be contained for a bottle of peppermint essential oil to be considered pharmaceutical grade, beyond menthol:
European pharmacopeial grade peppermint oil is the volatile oil distilled with steam from the fresh aerial parts of the flowering plant. Its relative density must be between 0.900 and 0.916, refractive index between 1.457 and 1.467, optical rotation between –10 and –30, among other quantitative standards. Identity must be confirmed by thin-layer chromatography (TLC), organoleptic evaluation, and quantitative analysis of internal composition by gas chromatography. It must contain 1.0–5.0% limonene, 3.5–14.0% cineole, 14.0–32.0% menthone, 1.0–9.0% menthofuran, 1.5–10.0% isomenthone, 2.8–10.0% menthylacetate, 30.0–55.0% menthol, maximum 4.0% pulegone, and maximum 1.0% carvone (Ph.Eur.3, 1997).French pharmacopeial grade peppermint oil must contain not less than 44% menthol, from 4.5–10% esters calculated as menthyl acetate, and from 15–32% carbonyl compounds calculated as menthone. TLC is used for identification, quantification of compounds, and verification of the absence of visible bands corresponding to carvone, pulegone, and isomenthone (Bruneton, 1995; Ph.Fr.X, 1990).132”
An example of how to use Table 1 for converting the .1-.2 ml indicated dosage to drops of essential oils is as follows:
· .2 ml of peppermint oil equates to approximately .067 oz (1 oz =30 ml).
· There are 600 drops of essential oil in one ounce.
· .067 oz of 600 drops totals approximately one drop two to three times a day. This equates to six to 12 drops per day.
Fennel Essential Oil
The American Botanical Council’s Expanded German E Commission reports on the dosage and administration for fennel essential oil110 as follows:
“Unless otherwise prescribed: 0.1-0.6 ml essential oil or equivalent Galenical preparations for internal use.
Essential oil: 0.1-0.6 ml.
Fennel honey or fennel syrup with 0.5 g fennel oil/kg [=0.5:1000 (w/w)]:
Adult: 10-20 g.
Children 4-10 years: 6-10 g.
Children 1-4 years: 3-6 g.
Duration of administration: Unless otherwise advised by a physician or pharmacist, one should not consume fennel oil for an extended period (several weeks).110”
Other sources do not contain direct references to dosage.
Oregano Essential Oil
Examine states the following regarding dosage for oregano oil:
“The only study on using oil of oregano for oral supplementation used a dose of 600 mg. To make tea, steep 15 g of oregano leaves in 250 mL of water.
The tea is traditionally used to aid digestion, while the oil has antibacterial properties that may boost the immune system.
Both the tea and oil is usually supplemented once a day.”
Since the study cited is based on an emulsified oil, not an essential oil, this information is misleading.133 Using Table 1:
· 1 drop = 30 mg.
· The dosage reported would be 600 mg/30 mg, which would equate to 20 drops of pure essential oil. This is not an ideal dose.133,134
I did find one human trial of 104 subjects that used oregano oil in a formulation. The study found the efficacy of herbal treatment to be equivalent to Rifaximin for treatment of SIBO. For the intervention, one of the two formulations randomized contained .1 ml of oregano oil. This would be equivalent to approximately .5-1 drop of oregano oil.151
Ginger Essential Oil
Neither of the monographs for ginger in Examine152 and the American Botanical Council’s Expanded German E Commission153 state a dosage for the internal usage of essential oil of ginger, as they do the herb. Natural Medicines Database authors report on nasocutaneous administration and inhalation of ginger oil as follows:
“Chemotherapy-induced nausea and vomiting: An aromatherapy necklace containing two drops of ginger essential oil has been used for 2 minutes three times daily for 5 days starting with chemotherapy.
Postoperative nausea and vomiting: A 5% solution of ginger essential oil, administered nasocutaneously, has been used preoperatively. Aromatherapy with ginger alone, or in combination with spearmint, peppermint, and cardamom, has been inhaled through the nose and exhaled through the mouth three times postoperatively.154”
The conversion of drops of essential oil in a 5% solution of ginger oil would be as follows:
· 1 oz. = 600 drops
· 6 drops of EO per oz. of carrier oil = 1% dilution (1% of 600 drops)
· 30 drops of EO per oz. of carrier oil= 5% dilution (5% of 600 drops)
Essential Oils and the Microbiome
Since healing the intestinal tract via the “Five R” program includes removing the cause (e.g., microbes) and re-inoculating the good bacteria, it is important to pause and discuss how essential oils, which are often deemed “antimicrobial,” impact the microbiome. From my research and experience, I believe that high quality essential oils likely balance microbe activity. Specifically, there is supporting evidence that as they eliminate overgrowth, they also spare commensal organisms and protect our tissues.
I will now provide a brief review of the scientific literature regarding this topic. First, I will give a quick summary on their antimicrobial actions and use with antibiotics. Then, I will provide the compelling vivo and in vitro trials. This, in combination with years of clinical experience and experts’ opinions, provides support for assisting with positively balancing the intestinal microbiome.
The Antimicrobial Properties of Essential Oils
The antimicrobial activity of essential oils on pathogenic bacteria is diverse. In a review on the effects, the authors differentiate the actions of essential oils (EOs) to their isolates. The authors state:
“The mechanism of action of EOs depends on their chemical composition, and their antimicrobial activity is not attributable to a unique mechanism but is instead a cascade of reactions involving the entire bacterial cell; together, these properties are referred to as the “essential oils versatility”. In general, EOs act to inhibit the growth of bacterial cells and also inhibit the production of toxic bacterial metabolites. Most EOs have a more powerful effect on Gram-positive bacteria than Gram-negative species, and this effect is most likely due to differences in the cell membrane compositions.155”
A proposed mechanism of essential oils on microbe destruction consists of their toxic effects on membrane structure. These include “degradation of the cell wall, damaging the cytoplasmic membrane, cytoplasm coagulation, damaging membrane proteins, increased permeability leading to leakage of cell contents, reducing proton motive force, reducing intracellular ATP pool via decreased ATP synthesis and augmented hydrolysis that is separate from the increased membrane permeability and reducing membrane potential via increased membrane permeability.”155
Essential oils have also been reported to interfere with quorum sensing (bacteria’s regulation of gene expression related to changes in cell-population density) and decrease bacterial virulence factors.155
They may also be helpful in combination with antibiotics to prevent resistance. In a 2014 article titled, “Essential Oils, A New Horizon in Combating Bacterial Antibiotic Resistance,” the authors explain that essential oils’ versatile properties make them a novel approach for a “drug compound.” This is because essential oils have more than one therapeutic effect due to their many biological impacts. This contrasts with a drug’s mechanism which is skewed to act on one pathway in the body, not accounting for effects on the body’s other functions. The article states:
“Various essential oils have been reviewed to possess different biological properties such as anti-inflammatory, sedative, digestive, antimicrobial, antiviral, antioxidant as well as cytotoxic activities. These findings highlight an exciting scientific interest whereby essential oils warrant special attention because they represent a distinctive group of possible novel drug compounds due to their chemical and structural variance that makes them functionally versatile.156”
Essential Oils Impact on Intestinal Microbes In Vitro
An in vitro study with eight essential oils, the authors sought to determine if essential oils selectively inhibited several microbes that cause intestinal dysbiosis while sparing 12 species of intestinal bacteria. The authors reported:157
“The most promising essential oils for the treatment of intestinal dysbiosis are Carum carvi, Lavandula angustifolia, Trachyspermum copticum, and Citrus aurantium var. amara. The herbs from which these oils are derived have long been used in the treatment of gastrointestinal symptoms and the in vitro results of this study suggest that their ingestion will have little detrimental impact on beneficial members of the GIT microflora. More research is needed, however, to investigate tolerability and safety concerns, and verify the selective action of these agents.157”
In a study with swine cecal digesta, the authors tested the antimicrobial effects of 66 essential oils and their impact on swine gut. The authors stated:
“The antimicrobial activity of essential oils/compounds was measured by determining the inhibition of bacterial growth. Among 66 essential oils/compounds that exhibited ≥80% inhibition towards Salmonellatyphimurium DT104 and Escherichia coli O157:H7, nine were further studied. Most of the oils/compounds demonstrated high efficacy against S. typhimurium DT104, E. coli O157:H7, and E. coli with K88 pili with little inhibition towards lactobacilli and bifidobacteria. They were also tolerant to the low pH. When mixed with pig cecal digesta, these oils/compounds retained their efficacy against E. coli O157:H7. In addition, they significantly inhibited E. coli and coliform bacteria in the digesta, but had little effect on the total number of lactobacilli and anaerobic bacteria.158”
Essential Oils Impact on Intestinal Flora In Vivo
In a 2010 in vivo study, it was demonstrated that ocotea essential oil inhibited inflammatory mediators from microbial byproducts while simultaneously protecting the gastric mucosa of rodents.159
In another study with rabbits, thyme oil increased antioxidant status (i.e., GPx activity) and decreased oxidative harm (i.e., lowered malondialdehyde) in the small intestine. It also positively influenced intestinal integrity, aka preventing “leaky gut,” as measured by transepithelial electrical resistance (TEER). Furthermore, there was a tendency “for thyme oil to stimulate the abundance of some microbes beneficial in the rabbit gut.” The abstract states:160
“In both groups, the bacterial counts were generally lower in the caecum than in the faecal samples. In conclusion, dietary supplementation with 0.5 g/kg DM thyme oil may improve intestinal integrity, and it may have an antioxidant effect. A tendency was also found for thyme oil to stimulate the abundance of some microbes beneficial in the rabbit gut. (Effect of thyme oil on small intestine integrity and antioxidant status, phagocytic activity and gastrointestinal microbiota in rabbits.160”
A study in chickens demonstrated that five culinary herbs and their essential oils (thyme, oregano, marjoram, rosemary, and yarrow) had negligible effects on gut microflora and beneficially impacted these broiler chicks’ digestion. In the experiment, body mass and feed consumption were measured on a weekly basis. Counts of lactic acid bacteria, coliforms, anaerobes, and Clostridum perfingens were assessed at 25 days. Finally, digestibilities were measured via nitrogen (N), dry matter (DM) and organic matter, and sialic acid concentration. The researchers concluded:161
“Generally, dietary thyme oil or yarrow herb inclusion had the most positive effects on chick performance, while oregano herb and yarrow oil were the poorest supplements. Only thyme and yarrow in these diets had a different effect when used as a herb or oil on weight gain and BM.4 Dietary treatment had no effect on the intestinal microflora populations, apparent metabolisable energy (AME) or the calculated coefficients of digestibility. Sialic acid concentration was greatest in the birds given dietary thyme oil, compared with all other treatments except those birds receiving marjoram oil, rosemary herb and the controls. However, less sialic acid was excreted in those birds given diets with oregano or rosemary oils, or oregano herb, than in the controls.5 Plant extracts in diets may therefore affect chick performance, gut health and endogenous secretions, although the chemical composition of the extract appears to be important in obtaining the optimal effects. (The effect of herbs and their associated essential oils on performance, dietary digestibility and gut microflora in chickens from 7 to 28 days of age).161”
My Clinical Experience:
How I Use Essential Oils Internally for Intestinal Discomfort
I find oral administration of essential oils the most effective method of application for clients that are seeking relief from symptoms of irritable bowel syndrome, functional gastrointestinal disorders, bloating and abdominal extension, food poisoning (due to antimicrobial effects noted above), discomfort, gas, dysbiosis, and changes in stool frequency.
I instruct my clients to administer one to two drops of the selected essential oil from a quality supplier. The drops are placed in a vegetable capsule (enteric coated) using pipette droppers. Next, they are asked to fill the remainder of the cap with coconut oil or a non-dairy milk substitute. This is important for sensitive patients, as it will provide coating for the stomach.
Essential oils are alternated every two months or until symptoms have resolved and lab markers are back within normal ranges. I also recommend that my clients take 1-2 days off per week depending on tolerance. If one experiences burping, GI discomfort, or notices loose stools, I will decrease the dose.
I often supplement any gut protocol with a relaxing essential oil to restore the nervous system. The most well-known and most researched essential oil for this is lavender.162-167
Lavender has a good reputation for alleviating anxiety Europe. Germany has authorized a preparation of lavender oil, Silexan, for treatment of restlessness during anxious mood.162-167 It is branded as LASEA and is standardized for 20-45% linalool and 25-46% linalyl acetate.162 Two trials have indicated that Silexan has been effective in mood related issues without unwanted sedative effects.165,166 According to Examine, “It is prescribed (or at least used) for Generalized Anxiety disorder in Germany without apparent benzodiazepene actions.”163
In a comprehensive review, the nervous system effects of lavender were analyzed in animal and human clinical trials. The authors reported that lavender was shown to have in vivo effects of modulating inflammatory pathways in the brain and on the neurotransmitters dopamine, GABA and serotonin. Human studies with functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) also indicated brain imaging evidence for relaxation effects. These calming effects were also shown to have an impact on sleep, pain, and positive mood.167
These psychoneurological effects will impact gastrointestinal function related to the gut-brain connection, stress, and resultant discomfort and pain.168
As far as dosage, both Examine and the American Botanical Council’s Herbal Expanded Commission E Commissions report that the internal dosage of lavender oil is between 80-160 mg of essential oil.162,163 Using the conversions in the table:
· 30 mg = approximately 1 drop of oil
· 80-160 mg would be approximately 3-6 drops of lavender oil
I have often also used this oil internally at these dosages for clients who appear to have hyperactive sympathetic activity, which is most of my IBS and pain clients.
Conclusion:
Summarizing the Art and Science of Selecting the “Correct” Essential Oil
Essential oils can effectively remove the obstacles in the way of healing via their multimodal effects while simultaneously and synergistically working with the body to bring it to balance. This is due to their biochemical constituents affecting physiology combined with the instantaneous psychological effect of their aroma.1-2
Not only are essential oils synergistic within themselves and with other modalities, they are also the same regarding their action with the human body. One human study provided evidence that the metabolomics and biochemical pathways of individuals were modulated differently by the same essential oil intervention.
In the clinical trial, researchers sought to determine the metabolic changes in thirty-one females with mild anxiety symptoms after exposure to aroma inhalation for 10 days. In several participants, no effect was found in the measurements studied, yet there were minimal disturbances and many benefits reported by all the responsive subjects. This demonstrates the mechanisms of essential oils “innate wisdom” to bring about balance to the human body. The authors concluded:169
“A significant alteration of metabolic profile in subjects responsive to essential oil was found, which is characterized by the increased levels of arginine, homocysteine, and betaine, as well as decreased levels of alcohols, carbohydrates, and organic acids in urine. Notably, the metabolites from tricarboxylic acid (TCA) cycle and gut microbial metabolism were significantly altered. This study demonstrates that the metabolomics approach can capture the subtle metabolic changes resulting from exposure to essential oils, which may lead to an improved mechanistic understanding of aromatherapy.169”
I have now provided evidence that essential oils can address underlying causes of dysfunction while simultaneously alleviating contributors, triggers, and mediators. I have shown this through the example of using them internally for intestinal discomfort. By reviewing what I have learned and my clinical experience for the past seventeen years, my hope is that now clinicians can decipher how to proceed with more informed, safe, and confident decisions on dosage and proper use of this powerful, ancient, innately intelligent, healing modality.
Sarah LoBisco, ND, is a graduate of the University of Bridgeport’s College of Naturopathic Medicine (UBCNM). She is licensed in Vermont as a naturopathic doctor and holds a bachelor of psychology degree from State University of New York at Geneseo. Dr. LoBisco is a speaker on integrative health, has several publications, and has earned her certification in functional medicine. Dr. LoBisco currently incorporates her training as a naturopathic doctor and functional medicine practitioner through writing, researching, private practice, and her independent contracting work for companies regarding supplements, nutraceuticals, essential oils, and medical foods. Dr. LoBisco also enjoys continuing to educate and empower her readers through her blogs and social media.
Her recent blog can be found at www.dr-lobisco.com.
References
1. LoBisco S. Sniffing Out Pain. Part 1: Olfaction’s Complex Connections of Emotions, Memory, and Pain Perception. Townsend Letter[online]. November 2016.
2. LoBisco S. Sniffing Out Pain: Part 2: The Multimodal Actions of Essential Oils on Pain Perception and Pain Relief. Townsend Letter [online]. December 2016.
3. Krusemark EA, Novak LR, Gitelman DR, Li W. When the Sense of Smell Meets Emotion: Anxiety-State-Dependent Olfactory Processing and Neural Circuitry Adaptation. Journal of Neuroscience. September 25, 2013; 33(39):15324-15332.
4. Matsunaga M, et al. Psychological and physiological responses to odor-evoked autobiographic memory. Neuro Endocrinol Lett. 2011;32(6):774-80.
5. National Cancer Institute – PDQ Cancer Information Summaries. Aromatherapy and Essential Oils (PDQ®) Health Professional Version. Last Update: October 16, 2012.
6. National Association for Holistic Aromatherapy. Exploring Aromatherapy: Regulations and Licensing. Available at: http://naha.org/explore-aromatherapy/regulations/. Accessed April 5, 2018.
7. National Association for Holistic Aromatherapy. Exploring Aromatherapy: Methods of Application. Available at: http://naha.org/explorearomatherapy/about-aromatherapy/methods-of-application/. Accessed April 5, 2018.
8. Alliance of International Aromatherapists. Aromatherapy. Alliance of International Aromatherapists. Available at: http://www.alliancearomatherapists.org/history-basics. Accessed April 7, 2018.
9. Robert Tisserand interviewed on ingestion, dilution and other safety issues. Robert Tisserand Web site. Available at: http://roberttisserand.com/2015/08/robert-tisserand-interviewed-on-ingestion-dilution-and-other-safety-issues/. Accessed July 2, 2018.
10. Miller K. Lavender and Tea Tree Essential Oils May Cause Male Breast Growth: Yes, you should be worried. Women’s Health Web site. Available at: https://www.womenshealthmag.com/health/a19480687/lavender-tea-tree-essential-oils-male-breast-growth/. Accessed March 28, 2018.
11. Lee B. Will Essential Oils Like Lavender and Tea Tree Make Your Breasts Larger. Forbes Web site. Available at: https://www.forbes.com/sites/brucelee/2018/03/18/will-essential-oils-like-lavender-and-tea-tree-make-your-breasts-larger/#3e238f323fc2. Accessed March 28, 2018.
12. Endocrine Society. Chemicals in lavender and tea tree oil appear to be hormone disruptors: Current Press Releases March 17, 2018. Endocrine Society Web site. Available at: https://www.endocrine.org/news-room/2018/chemicals-in-lavender-and-tea-tree-oil-appear-to-be-hormone-disruptors. Accessed March 28, 2018.
13. Endocrine Society. Chemicals in lavender and tea tree oil appear to be hormone disruptors. ScienceDaily. Available at: https://www.sciencedaily.com/releases/2018/03/180318144856.htm. Accessed March 28, 2018.
14. Henley DV, et al. Prebubertal gynecomastia linked to lavender and tea tree oils. New England Journal of Medicine. 2007; 365(5): 479-485.
15. Tisserand R. Lavender oil is not estrogenic. Robert Tisserand Web site. Available at: http://roberttisserand.com/2013/02/lavender-oil-is-not-estrogenic/. Accessed March 28, 2018.
16. LoBisco S. Why Lavender Essential Oil Won’t Cause Your Boys’ Breasts to Develop [Web page]. Living Well at Saratoga.com Web site. Available at: https://www.saratoga.com/living-well/2016/01/why-lavender-essential-oil-wont-cause-your-boys-breasts-to-develop/. Accessed March 23, 2018.
17. LoBisco, S. The Safety of Sage Essential Oil Part I: Camphor, Thujone, “Toxicity” Oh My! Healing, Health, and Wellness for the Body, Mind, and Spirit with Dr. Sarah. May 1, 2018. Available at: https://www.saratoga.com/healing-health-wellness/2018/05/the-safety-of-sage-essential-oil-part-i-camphor-thujone-toxicity-oh-my/. Accessed July 1, 2018.
18. LoBisco, S. Sage Oil Safety Vindicated. BreakFree Medicine Website. May 4, 2018. Available at: http://dr-lobisco.com/sage-oil-safety-vindicated/. Accessed August 1, 2018.
19. Gori L, et al. Can Estragole in Fennel Seed Decoctions Really Be Considered a Danger for Human Health? A Fennel Safety Update. Evidence-based Complementary and Alternative Medicine : eCAM. 2012;2012:860542. doi:10.1155/2012/860542.
20. Timm M, et al. Considerations regarding use of solvents in in vitro cell based assays. Cytotechnology. 2013;65(5):887-894. doi:10.1007/s10616-012-9530-6.
21. Di Bella G, et al. Production process contamination of citrus essential oils by plastic materials [abstract]. J Agric Food Chem [online]. 2001 Aug;49(8):3705-8.
22. Hamidpour M, et al. Chemistry, Pharmacology, and Medicinal Property of Sage (Salvia) to Prevent and Cure Illnesses such as Obesity, Diabetes, Depression, Dementia, Lupus, Autism, Heart Disease, and Cancer. Journal of Traditional and Complementary Medicine. 2014;4(2):82-88.
23. Manoguerra AS, et al. American Association of Poison Control Centers. Camphor Poisoning: an evidence-based practice guideline for outof-hospital management[abstract]. Clin Toxicol (Phila) [online]. 2006;44(4):357-70.
24. Canadian Centre for Occupational Health and Safety. OSH Answer Facts Sheets: Synergism [Web page]. Canadian Center for Occupational Health and Safety Web site. Available at: https://www.ccohs.ca/oshanswers/chemicals/synergism.html. Accessed March 29, 2018.
25. Zhang Y, et al. Assessing the Metabolic Effects of Aromatherapy in Human Volunteers. Evidence-Based Complementary and Alternative Medicine. 2013; 2013: Article ID 356381. doi:10.1155/2013/356381
26. Ali B, et al. Essential oils used in aromatherapy: A systemic review. Asian Pacific Journal of Tropical Biomedicine. 2015;5(8): 601-611.
27. Etman M, et al. Emulsions and rectal formulations containing myrrh essential oil for better patient compliance. Drug Discov Ther. 2011 ;5(3):150-156.
28. Dundar E, et al. The effects of intra-rectal and intra-peritoneal application of Origanum onites L. essential oil on 2,4,6- trinitrobenzenesulfonic acid-induced colitis in the rat. Exp Toxicol Pathol. 2008 Apr;59(6):399-408.
29. National Association for Holistic Aromatherapy. Exploring Aromatherapy: Safety Information. NAHA Web site. Available at: https://naha.org/explore-aromatherapy/safety/. Accessed July 25, 2018.
30. U.S. Food & Drug Administration. Pharmaceutical Quality/Manufacturing Standards (CGMP). FDA Website. Updated October 16, 2017. Available at: https://www.fda.gov/drugs/guidancecomplianceregulatoryinformation/guidances/ucm064971.htm. Accessed April 1, 2018.
31. U.S. Food & Drug Administration. Office of Pharmaceutical Quality. FDA Website. Updated March 28, 2018. Available at: https://www.fda.gov/AboutFDA/CentersOffices/OfficeofMedicalProductsandTobacco/CDER/ucm418347.htm. Accessed April 2, 2018.
32. Makary MA, Danie M. Medical error—the third leading cause of death in the US. BMJ. 2016; 353 doi: https://doi.org/10.1136/bmj.i2139.
33. WebMD. Drug Side Effects Explained. WebMD Website. Available at: https://www.webmd.com/a-to-z-guides/drug-side-effectsexplained#1. Accessed April 18, 2018.
34. Food and Drug Administration. CFR – Code of Federal Regulations Title 21. FDA Web site. Available at: https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=182.2. Accessed May 2, 2018.
35. Food and Drug Administration. How FDA Evaluates Regulated Products: Drugs. FDA Web site. Available at: http://www.fda.gov/AboutFDA/Transparency/Basics/ucm269834.htm. Accessed March 6, 2018.
36. International Standardization Organization. ISO/TC 54 – Essential oils. ISO Web site. Available at: http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_tc_browse.htm?commid=48956. Accessed December 2, 2017.
37. Mori M, et al. Quality Evaluation of Essential Oils. YAKUGAKU ZASSHI. 2002; 122(3): 253-261. Article in Japanese. Available at: https://www.jstage.jst.go.jp/article/yakushi/122/3/122_3_253/_pdf/-char/ja
38. International Organization for Standardization. About ISO. ISO Web site. Available at: https://www.iso.org/about-us.html. Accessed July 26, 2018.
39. Association of French Normalization Organization. Standards- All Published Standards. AFNOR Web site. Available at: http://www.afnor.org/en/profiles/activity area/industry/normes/normes/%28limit%29/25/%28page%29/2 =. Accessed December 2, 2017.
40. Association of French Normalization Organization. ISO 9001 Certification – Quality. AFNOR Web site. Available at: http://www.afnor.org/en/certification/smq001#p17578. Accessed March 15, 2018.
41. Association of French Normalization Organization. Normes. AFNOR Web site. Available at: http://www.boutique.afnor.org/recherche/resultats/categorie/normes/ics/huiles-essentielles71.100.60%20?utm_source=portail&utm_medium=referral&utm_campaign=editions. Accessed March 15, 2018.
42. Stewart, D. The Chemistry of Essential Oils Made Simple: God’s Love Manifest in Molecules. Marble Hill, MO. 2005. Care Publications.
43. Tisserand R, Young R. Essential Oil Safety – E-Book: A Guide for Health Care Professionals. Churchill Livingston Elsevier. 2014. Available online at: https://books.google.com/books?id=DbEKAQAAQBAJ&printsec=frontcover#v=onepage&q&f=false
44. Shutes, J. The Quality of Essential Oils. The School for Aromatic Studies. Website. Available at: https://aromaticstudies.com/the-quality-of-essential-oils/. Accessed July 14, 2018.
45. Sampaio BL, Edrada-Ebel R, Da Costa FB. Effect of the environment on the secondary metabolic profile of Tithonia diversifolia: a model for environmental metabolomics of plants. Scientific Reports. 2016;6:29265. doi:10.1038/srep29265.
46. Figueiredo AC, et al. Factors affecting secondary metabolite production in plants: Volatile components and essential oils. Flavour and Fragrance Journal. 2008; 20(4): 213-226.
47. K. Husnu Can Baser, Gerhard Buchbauer ed. Handbook of Essential Oils: Science, Technology, and Applications, Second Edition. CRC Press: Taylor and Francis Group. Boca Ranton, FL. 2016.
48. Young Living Essential Oils (YLEO). Young Living Seed to Seal: Standards Far Above the Standards. YLEO Website. Available at: https://www.youngliving.com/en_US/discover/seed-to-seal. Accessed July 28, 2018.
49. Medication Administration: Why It’s Important to Take Drugs the Right Way. Healthline. Available at: https://www.healthline.com/health/administration-of-medication. Accessed April 1, 2018.
50. Federico F. The Five Rights of Medication Administration. Institute for Healthcare Improvement. Available at: http://www.ihi.org/resources/Pages/ImprovementStories/FiveRightsofMedicationAdministration.aspx. Accessed April 3, 2018.
51. Grissinger M. The Five Rights: A Destination Without a Map. Pharmacy and Therapeutics. 2010;35(10):542.
52. Fernandez E, et al. Factors and Mechanisms for Pharmacokinetic Differences between Pediatric Population and Adults. Pharmaceutics. 2011;3(1):53-72. doi:10.3390/pharmaceutics3010053.
53. Dorne JL. Impact of inter-individual differences in drug metabolism and pharmacokinetics on safety evaluation [abstract]. Fundam Clin Pharmacol [online]. 2004 Dec;18(6):609-20.
54. Klotz U. Pharmacokinetics and drug metabolism in the elderly. Drug Metab Rev. 2009;41(2):67-76.
55. Ward E. Addressing nutritional gaps with multivitamin and mineral supplements. Nutrition Journal. 2014;13:72.
56. Richardson RA, Davidson H. Nutritional demands in acute and chronic illness. Proc Nutr Soc. 2003 Nov;62(4):777-81.
57. Mohn ES, et al. Evidence of Drug–Nutrient Interactions with Chronic Use of Commonly Prescribed Medications: An Update. Pharmaceutics. 2018; 10(1), 36; doi:10.3390/pharmaceutics10010036.
58. Ni Y, et al. NutriChem 2.0: exploring the effect of plant-based foods on human health and drug efficacy. Database: The Journal of Biological Databases and Curation. 2017;2017:bax044. doi:10.1093/database/bax044.
59. Pauli A, Schilcher H. Specific Selection of Essential Oil Compounds for Treatment of Children’s Infection Diseases. Pharmaceuticals. 2004;1(1):1-30.
60. D Mas. Chapter 1: Introduction to Chamomile. Chamomile. In: Medicinal, Biochemical, and Agricultural Aspects. Boca Raton, FL. CRC Press; 2015: 1-48. Available online at: http://abc.herbalgram.org/site/DocServer/CRCPRESSChamomile-Section_1.5978-1-4665-7759- 6.pdf?docID=6362. Accessed July 28, 2018.
61. Matricaria chamomilla (German chamomile). Monograph. Altern Med Rev. 2008 Mar;13(1):58-62. Available at: http://archive.foundationalmedicinereview.com/publications/13/1/58.pdf. Accessed August 1, 2018.
62. Srivastava JK, Shankar E, Gupta S. Chamomile: A herbal medicine of the past with bright future. Molecular medicine reports. 2010;3(6):895-901. doi:10.3892/mmr.2010.377.
63. Natural Medicines. German Chamomile Monograph. Available at: https://naturalmedicines.therapeuticresearch.com/databases/food,-herbssupplements/professional.aspx?productid=951#interactionsWithDrugs. Accessed August 1, 2018.
64. Schneider P, Stuppner H, Ganzera M. Inhibitory effects of the essential oil of chamomile (Matricaria recutita L.) and its major constituents on human cytochrome P450 enzymes. Life Sciences. 2006 Feb; 78(8):856-61.
65. Fan H. Authenticity analysis of citrus essential oils by HPLC -MS on oxygenated heterocyclic components. Journal of Food and Drug Analysis. 2012; 23(1):30-39.
66. Sun J. D-Limonene: Safety and Clinical Applications. Alternative Medicine Review. 2007; 12(3). Available at: http://www.altmedrev.com/archive/publications/12/3/259.pdf. Accessed July 1, 2018.
67. Dugrand-Judek A, et al. The Distribution of Coumarins and Furanocoumarins in Citrus Species Closely Matches Citrus Phylogeny and Reflects the Organization of Biosynthetic Pathways. Chen C, ed. PLoS ONE. 2015;10(11):e0142757. doi:10.1371/journal.pone.0142757.
68. Bailey DG, Dresser J, Arnold MO. Grapefruit-medication interactions: Forbidden fruit or avoidable consequences? CMAJ. November 2- UV 6, 2012.
69. Williamson, EA. Inhibition of Cytochrome P450 2E1, Cytochrome P450 3A6 and Cytochrome P450 2A6 by Citrus Essential Oils. [Thesis] The University of North Carolina at Greensboro (UNCG ) Advisor: Gregory M. Raner. 2010; 66 pgs. Available at: https://libres.uncg.edu/ir/uncg/f/Williamson_uncg_0154M_10494.pdf. Accessed May 30, 2018.
70. IARC. D-limonone. IARC Monographs. Volume 73. Available at: https://monographs.iarc.fr/ENG/Monographs/vol73/mono73-16.pdf. Accessed August 1, 2018.
71. Examine. Limonene. Examine.com. Available at: https://examine.com/supplements/limonene/. Accessed August 8, 2018.
72. Miyazawa M, Shindo M, Shimada T. Sex differences in the metabolism of (+)- and (-)-limonene enantiomers to carveol and perillyl alcohol derivatives by cytochrome p450 enzymes in rat liver microsomes [abstract]. Chem Res Toxicol [online]. 2002 Jan;15(1):15-20.
73. Lupien S, et al. Cytochrome P450 limonene hydroxylases of Mentha species [abstract]. Drug Metabol Drug Interact [online]. 1995;12(3- 4):245-60.
74. Cytochrome P450 (E.C. 1.14.-.-). British Journal of Pharmacology. 2009;158(Suppl 1):S215-S217. doi:10.1111/j.1476- 5381.2009.005068.x.
75. Miyazawa M, Shindo M, Shimada T. Metabolism of (+)- and (−)-Limonenes to Respective Carveols and Perillyl Alcohols by CYP2C9 and CYP2C19 in Human Liver Microsomes. Drug Metabolism and Disposition.May 2002; 30(5): 602-607.
76. Natural Medicines. Limonene Monograph. Available at: https://naturalmedicines.therapeuticresearch.com/databases/food,-herbssupplements/professional.aspx?productid=1105#interactionsWithDrugs. Accessed July 3, 2018.
77. New York Institute for Aromatic Studies. Synergism in essential oils and aromatherapy. Available at: https://aromaticstudies.com/synergism-in-essential-oils-and-aromatherapy/. Accessed March 3, 2018.
78. Yap PSX, Yiap BC, Ping HC, Lim SHE. Essential Oils, A New Horizon in Combating Bacterial Antibiotic Resistance. The Open Microbiology Journal. 2014;8:6-14. doi:10.2174/1874285801408010006.
79. Examine. Lavender. Examine. Com. Available at: https://examine.com/supplements/lavender/. Accessed August 1, 2018.
80. Examine. Peppermint. Examine.com. Available at: https://examine.com/supplements/peppermint/. Accessed August 1, 2018.
81. Dresser GK, Wacher V, Wong S, Wong HT, Bailey DG..Evaluation of peppermint oil and ascorbyl palmitate as inhibitors of cytochrome P4503A4 activity in vitro and in vivo [abstract]. Clin Pharmacol Ther [online]. 2002. Sep;72(3):247-55.
82. Elmore, L. Effects of Essential Oils on the Liver. Lindsey Elmore web site. May 19, 2018. Available at: https://lindseyelmore.com/effects-of-essential-oils-on-the-liver/. Accessed May 28, 2018.
83. LoBisco S. Are Essential Oils Safe for Children (and Adults)? November 25, 2015. Available at: https://dr-lobisco.com/are-essential-oils-safe/. Accessed July 2, 2018.
84. Shin N-Y, et al. Protein Targets of Reactive Electrophiles in Human Liver Microsomes. Chemical research in toxicology. 2007;20(6):859-867. doi:10.1021/tx700031r.
85. Ketterer B, Coles B, Meyer DJ. The role of glutathione in detoxication. Environmental Health Perspectives. 1983;49:59-69.
86. He NG, et al. The role of glutathione S-transferases as a defense against reactive electrophiles in the blood vessel wall [abstract]. Toxicol Appl Pharmacol [online]. 1998 Sep;152(1):83-9. Available at: https://www.ncbi.nlm.nih.gov/pubmed/9772203. Accessed March 21, 2018.
87. Ketterer B. Glutathione S-transferases and prevention of cellular free radical damage [abstract]. Free Radic Res [online]. 1998 Jun;28(6):647-58.
88. Nakamura Y, et al. A phase II detoxification enzyme inducer from lemongrass: identification of citral and involvement of electrophilic reaction in the enzyme induction [abstract]. Biochem Biophys Res Commun [online]. 2003 Mar 14;302(3):593-600. Available at: https://www.ncbi.nlm.nih.gov/m/pubmed/12615076/. Accessed April 17, 2018.
89. Thusoo S, et al. Antioxidant Activity of Essential Oil and Extracts of Valeriana jatamansi Roots. BioMed Research International. 2014;2014:614187. doi:10.1155/2014/614187.
90. Gonçalves RS, et al. Antioxidant properties of essential oils from Mentha species evidenced by electrochemical methods. Revista Brasileira de Plantas Medicinais. 2009; 11(4), 372-382.
91. Misharina TA, et al. [Effects of low doses of essential oil on the antioxidant state of the erythrocytes, liver, and the brains of mice] [online]. Prikl Biokhim Mikrobiol [online]. [Article in Russian]. 2014 Jan-Feb;50(1):101-7. Available at: https://www.ncbi.nlm.nih.gov/pubmed/25272759. Accessed April 2, 2018.
92. El-Hosseiny LS, Alqurashy NN, Sheweita SA. Oxidative Stress Alleviation by Sage Essential Oil in Co-amoxiclav induced Hepatotoxicity in Rats. International Journal of Biomedical Science: IJBS. 2016;12(2):71-78.
93. Sultan MT, Butt MS, Karim R, et al. Nigella sativa fixed and essential oil modulates glutathione redox enzymes in potassium bromate induced oxidative stress. BMC Complementary and Alternative Medicine. 2015;15:330. doi:10.1186/s12906-015-0853-7.
94. Sheweita SA, El-Hosseiny LS, Nashashibi MA. Protective Effects of Essential Oils as Natural Antioxidants against Hepatotoxicity Induced by Cyclophosphamide in Mice. Lehmler H-J, ed. PLoS ONE. 2016;11(11):e0165667. doi:10.1371/journal.pone.0165667.
95. Amorati R, Foti MC, Valgimigli L. Antioxidant activity of essential oils [abstract]. J Agric Food Chem [online]. 2013 Nov 20;61(46):10835-47. doi: 10.1021/jf403496k.
96. Atsumi T, Tonosaki K. Smelling lavender and rosemary increases free radical scavenging activity and decreases cortisol level in saliva. Psychiatry Res. 2007 Feb 28;150(1):89-96.
97. Elmore L. 50 Answers to Common Questions About Essential Oils. Growing Healthy Homes. Bartlesville, OK. 2017.
98. Weinshilboum, RM. Phenol sulfotransferase in humans: properties, regulation, and function [abstract]. Fed Proc [online]. 1986 Jul;45(8):2223-8.
99. Sundaram RS, et al. Human intestinal phenol sulfotransferase: assay conditions, activity levels and partial purification of the thermolabile form. Drug Metab Dispos. 1989 May-Jun;17(3):255-64.
100. Court MH. Feline drug metabolism and disposition: pharmacokinetic evidence for species differences and molecular mechanisms. Veterinary Clinics of North America: Small Animal Practice. 2013; 43(5), 1–20.
101. Djilani A, Dicko A. The Therapeutic Benefits of Essential Oils, Nutrition, Well-Being and Health. Dr. Jaouad Bouayed ed. 2012; 160.
102. Jacobson L. Essential oils which inhibit blood clotting. Using Essential Oils Safely. April 23, 2015. Available at: https://www.usingeossafely.com/essential-oils-which-inhibit-blood-clotting/. Accessed July 1, 2018.
103. Webb NJ, Pitt WR. Eucalyptus oil poisoning in childhood: 41 cases in south-east Queensland. J Paediatr Child Health. 1993 Oct;29(5):368-71.
104. Jacobs MR, Hornfeldt CS. Melaleuca oil poisoning. J Toxicol Clin Toxicol. 1994;32(4):461-4.
105. Olleveant NA, Humphris G, Roe B. How big is a drop? A volumetric assay of essential oils [abstract]. J Clin Nurs [online]. 1999 May;8(3):299-304.
106. Lis-Balchin M. Essential oils and ‘aromatherapy’: their modern role in healing [abstract]. J R Soc Health [online]. 1997 Oct;117(5):324- 9.
107. Lis-Balchin M. Possible health and safety problems in the use of novel plant essential oils and extracts in aromatherapy [abstract]. J R Soc Promot Health [online]. 1999 Dec;119(4):240-3. Available at: https://www.ncbi.nlm.nih.gov/pubmed/10673845. Accessed August 1, 2018.
108. Halcón LL. Aromatherapy: therapeutic applications of plant essential oils [abstract]. Minn Med [online]. 2002 Nov;85(11):42-6. Available at: https://www.ncbi.nlm.nih.gov/pubmed/12498066. Accessed August 18, 2018.
109. Maddocks-Jennings W, Wilkinson JM. Aromatherapy practice in nursing: literature review. J Adv Nurs. 2004 Oct;48(1):93-103.
110. American Botanical Council. Herbal Medicine: Expanded Commission E. Fennel Oil. Available at: http://cms.herbalgram.org/expandedE/Fenneloil.html. Accessed April 2, 2018.
111. Foeniculum vulgare: A comprehensive review of its traditional use, phytochemistry, pharmacology, and safety. Arabian Journal of Chemistry. November 2016. Available at: http://www.sciencedirect.com/science/article/pii/S1878535212000792
112. Fennel. Natural Standard Database. Available at: https://naturalmedicines.therapeuticresearch.com/databases/food,-herbssupplements/professional.aspx?productid=311. Accessed July 16, 2018.
113. Examine. Fennel Oil. Examine.com. Available at: https://examine.com/supplements/fennel-essential-oil/#summary1-1. Accessed April 18, 2018.
114. Alexandrovich I, et al. The effect of fennel (Foeniculum Vulgare) seed oil emulsion in infantile colic: a randomized, placebo-controlled study. Altern Ther Health Med. 2003 Jul-Aug;9(4):58-61.
115. Mark Blumenthal: Quality and Efficacy of Herbal Medicines: Interview by Craig Gustafson. Integrative Medicine. 2015; 14:4. Available at: http://www.imjournal.com/openaccess/quality_and_efficacy_of_herbal_medicines.pdf
116. Blumenthal M, Busse WR, Goldberg A, Gruenwald J, Hall T, Riggins CW, et al; eds. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicine. 685 pages. Austin, TX: American Botanical Council; 1998. ISBN 096555550X.
117. Mountain Rose Herbs. Essential Oils and Dilution & Conversions Guides. Mountain Rose Herbs [Website]. Available at: https://blog.mountainroseherbs.com/dilutions-conversions. Accessed July 28, 2018.
118. Shutes J. Exploring Aromatherapy: Methods of Application. National Association for Holistic Aromatherapy. Available at: https://naha.org/explore-aromatherapy/about-aromatherapy/methods-of-application. Accessed July 28, 2018.
119. Jacobson L. Diluting Essential Oils Safely – safe dilution guidelines for all ages. Using Essential Oils Safely [Website]. April 2, 2015. Available at: http://www.usingeossafely.com/diluting-essential-oils-safely-safe-dilution-guidelines-for-all-ages/. Accessed July 28, 2018.
120. Rocky Mountain Oils. Essential Oil Dilution. Rocky Mountain Oils [Website]. Available at: https://www.rockymountainoils.com/dilution-rate/. Accessed July 28, 2018.
121. Zielinski E. Aromatherapy Essential Oils 101 – Guide to Safe and Effective Use. Dr. Eriz Z Web site. Available at: https://drericz.com/aromatherapy-essential-oils/. Accessed July 28, 2018.
122. Carnahan, J. Restoring Digestive Health with the 5-R Program. Dr. Jill. May 2011. Available at: https://www.jillcarnahan.com/2011/05/03/restoring-digestive-health/. Accessed May 1, 2018.
123. Bland J. The Gut Mucosal Firewall and Functional Medicine. Integrative Medicine: A Clinician’s Journal. 2016;15(4):19-22.
124. Metagenics Institute. 5R GI Restoration Program Guide. Gastrointestinal Health. Metagenics. 2013. Available at: http://www.oakwayhealthcenter.com/store/GUIDES_GI_Sustain_Guide.pdf. Accessed May 1, 2018.
125. Force M, Sparks WS, Ronzio RA. Inhibition of enteric parasites by emulsified oil of oregano in vivo [abstract]. Phytother Res [online]. 2000 May;14(3):213-4.
126. Schillaci D, et al. Origanum vulgare subsp. hirtum essential oil prevented biofilm formation and showed antibacterial activity against planktonic and sessile bacterial cells. J Food Prot. 2013 October; 76(10):1747-52.
127. Becerril R, Nerín C, Gómez-Lus R. Evaluation of bacterial resistance to essential oils and antibiotics after exposure to oregano and cinnamon essential oils. Foodborne Pathog Dis. 2012;9(8):699-705. doi: 10.1089/fpd.2011.1097.
128. Goerg KJ, Spilker TH. Effect of peppermint oil and caraway oil on gastrointestinal motility in healthy volunteers: a pharmacodynamic study using simultaneous determination of gastric and gall-bladder emptying and orocaecal transit time. Aliment Pharmacol Ther. 2003; 17: 445–451.
129. Ferrari N, ed. Health benefits of peppermint. Harvard Medical School HealthBeat. July 30, 2007.
130. Shams R, Oldfield E, Copare J, Johnson DA. Peppermint oil: clinical uses in the treatment of gastrointestinal diseases. JSM Gastroenterol Hepatol. 2015. Available at: http://www.jscimedcentral.com/Gastroenterology/gastroenterology-3-1036.pdf. Accessed July 20, 2016.
131. Examine. Summary of Peppermint. Examine. Com. Available at: https://examine.com/supplements/peppermint/. Accessed July 7, 2018.
132. American Botanical Council. Herbal Medicine: Expanded Commission E. Peppermint Oil. Available at: http://cms.herbalgram.org/expandedE/Peppermintoil.html#Administration. Accessed July 6, 2018.
133. Examine. Origanum vulgare. Examine.com. Available at: https://examine.com/supplements/origanum-vulgare/. Accessed July 15, 2018.
134. Natural Medicines. Oregano Monograph. Available at: https://naturalmedicines.therapeuticresearch.com/databases/food,-herbssupplements/professional.aspx?productid=644#dosing. Accessed July 7, 2018.
135. Mooyottu S, et al. Protective Effect of Carvacrol against Gut Dysbiosis and Clostridium difficile Associated Disease in a Mouse Model. Frontiers in Microbiology. 2017;8:625. doi:10.3389/fmicb.2017.00625.
136. Zou Y, et al. Oregano Essential Oil Improves Intestinal Morphology and Expression of Tight Junction Proteins Associated with Modulation of Selected Intestinal Bacteria and Immune Status in a Pig Model. BioMed Research International. 2016;2016:5436738. doi:10.1155/2016/5436738.
137. Wu KL, et al. Effects of ginger on gastric emptying and motility in healthy humans. Eur J Gastroenterol Hepatol. 2008 May;20(5):436- 40. doi: 10.1097/MEG.0b013e3282f4b224.
138. Sasidharan I, Nirmala Menon A. Comparative chemical composition and antimicrobial activity fresh & dry ginger oils (zigiber officinale roscoe) International Journal of Current Pharmaceutical Research. 2010;2:40–43.
139. Bode AM, Dong Z. The Amazing and Mighty Ginger. In: Benzie IFF, Wachtel-Galor S, editors. Herbal Medicine: Biomolecular and Clinical Aspects. 2nd edition. Boca Raton (FL): CRC Press/Taylor & Francis; 2011. Chapter 7. Available from: http://www.ncbi.nlm.nih.gov/books/NBK92775/
140. Liju VB, Jeena K, Kuttan R. Gastroprotective activity of essential oils from turmeric and ginger. J Basic Clin Physiol Pharmacol. 2015 Jan;26(1):95-103. doi: 10.1515/jbcpp-2013-0165.
141. Höferl M, et al. Composition and Comprehensive Antioxidant Activity of Ginger (Zingiber officinale) Essential Oil from Ecuador. Nat Prod Commun. 2015 Jun;10(6):1085-90.
142. Lua PL, Zakaria NS. A brief review of current scientific evidence involving aromatherapy use for nausea and vomiting [abstract]. J Altern Complement Med [online]. 2012 Jun;18(6):534-40. doi: 10.1089/acm.2010.0862.
143. Agah S, Taleb AM, Moeini R, Gorji N, Nikbakht H. Cumin Extract for Symptom Control in Patients with Irritable Bowel Syndrome: A Case Series. Middle East Journal of Digestive Diseases. 2013;5(4):217-222.
144. Eisenman SW, et al. Qualitative variation of anti-diabetic compounds in different tarragon (Artemisia dracunculus) cytotypes. Fitoterapia. 2011;82(7):1062-1074. doi:10.1016/j.fitote.2011.07.003.
145. Effects of garlic and juniper berry essential oils on ruminal fermentation and on the site and extent of digestion in lactating cows. J Dairy Sci. 2007 Dec;90(12):5671-81.
146. Sac Fernandes C, De Souza H, De Oliveria G, Costa J, Kerntopf M, Campos A. Investigation of the Mechanisms Underlying the Gastroprotective Effect of Cymbopogon Citratus Essential Oil. Journal of Young Pharmacists: JYP. 2012;4(1):28-32. doi:10.4103/0975- 1483.93578.
147. Wanapat M, et al. Manipulation of rumen ecology by dietary lemongrass (Cymbopogon citratus Stapf.) powder supplementation. J Anim Sci. 2008 Dec;86(12):3497-503. doi: 10.2527/jas.2008-0885.
148. Boukhatem MN, et al. Lemongrass (Cymbopogon citratus) essential oil as a potent anti-inflammatory and antifungal drugs. The Libyan Journal of Medicine. 2014;9:10.3402/ljm.v9.25431. doi:10.3402/ljm.v9.25431.
149. Boukhatem MN, et al. Lemongrass (Cymbopogon citratus) essential oil as a potent anti-inflammatory and antifungal drugs. The Libyan Journal of Medicine. 2014;9:10.3402/ljm.v9.25431. doi:10.3402/ljm.v9.25431.
150. Shojaii A, Abdollahi Fard M. Review of Pharmacological Properties and Chemical Constituents of Pimpinella anisum. ISRN Pharmaceutics. 2012;2012:510795. doi:10.5402/2012/510795.
151. Chedid V, Dhalla S, Clarke JO, et al. Herbal Therapy Is Equivalent to Rifaximin for the Treatment of Small Intestinal Bacterial Overgrowth. Global Advances in Health and Medicine. 2014;3(3):16-24. doi:10.7453/gahmj.2014.019.
152. Examine. Ginger Professional Monograph. Examine.com. Available at: https://examine.com/supplements/ginger/. Accessed April 7, 2018.
153. American Botanical Council. Herbal Medicine: Expanded Commission E. Ginger Root. Available at: http://cms.herbalgram.org/expandedE/Gingerroot.html#Administration. Accessed March 29, 2011.
154. Natural Medicines. Ginger. Available at: https://naturalmedicines.therapeuticresearch.com/databases/food,-herbssupplements/professional.aspx?productid=961#dosing. Accessed March 29, 201.
155. Nazzaro F, Fratianni F, De Martino L, Coppola R, De Feo V. Effect of Essential Oils on Pathogenic Bacteria. Pharmaceuticals. 2013;6(12):1451-1474. doi:10.3390/ph6121451.
156. Yap PSX, Yiap BC, Ping HC, Lim SHE. Essential Oils, A New Horizon in Combating Bacterial Antibiotic Resistance. The Open Microbiology Journal. 2014;8:6-14. doi:10.2174/1874285801408010006.
157. Hawrelak JA, Cattley T, Myers SP. Essential oils in the treatment of intestinal dysbiosis: A preliminary in vitro study. Altern Med Rev. 2009 Dec;14(4):380-4.
158. Si W, et al. Antimicrobial activity of essential oils and structurally related synthetic food additives towards selected pathogenic and beneficial gut bacteria. Journal of Applied Microbiology. December 2015.
159. Ballabeni V, et al. Ocotea quixos Lam. essential oil: in vitro and in vivo investigation on its anti-inflammatory properties [abstract]. Fitoterapia [online]. 2010 Jun;81(4):289-95.
160. Placha I, et al. Effect of thyme oil on small intestine integrity and antioxidant status, phagocytic activity and gastrointestinal microbiota in rabbits. Acta Vet Hung. 2013 Jun;61(2):197-208)
161. Cross DE, et al. The effect of herbs and their associated essential oils on performance, dietary digestibility and gut microflora in chickens from 7 to 28 days of age. Br Poult Sci. 2007 Aug;48(4):496-506.
162. American Botanical Council. Herbal Medicine: Expanded Commission E. Lavender flower. Available at: http://cms.herbalgram.org/expandedE/Lavenderflower.html. Accessed August 1, 2018.
163. Examine. Lavender. Examine.com. Available at: https://examine.com/supplements/lavender/. Accessed August 3, 2018.
164. Natural Medicines. Lavender Mongraph. Available at: https://naturalmedicines.therapeuticresearch.com/databases/food,-herbssupplements/professional.aspx?productid=838#dosing. Accessed August 2, 2018.
165. Uehleke B, et al. Phase II trial on the effects of Silexan in patients with neurasthenia, post-traumatic stress disorder or somatization disorder. Phytomedicine. 2012 Jun 15;19(8-9):665-71. doi: 10.1016/j.phymed.2012.02.020.
166. Kasper S, et al. Silexan, an orally administered Lavandula oil preparation, is effective in the treatment of ‘subsyndromal’ anxiety disorder: a randomized, double-blind, placebo controlled trial. Int Clin Psychopharmacol. 2010 Sep;25(5):277-87.
167. Koulivand PH, Khaleghi Ghadiri M, Gorji A. Lavender and the nervous system. Evidence-based Complementary and Alternative Medicine: eCAM. 2013;2013:681304.
168. Mayer LA. The neurobiology of stress and gastrointestinal disease. Gut.2000;47:861-869.
169. Zhang Y, et al. Assessing the Metabolic Effects of Aromatherapy in Human Volunteers. Evidence-Based Complementary and Alternative Medicine. 2013: 2013, Article ID 356381, 9 pages.
