References (for Parts 1 and 2 .pdf) were not in our print edition.
Editor note: Part 1 of this article discusses issues of safety, essential oil quality, metabolism, and synergy when using essential oils orally. Part 2, published in our January issue, looks at the clinical application of ingested essential oils for intestinal discomfort.
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Last year, I had the privilege to write a two-part article series for Townsend Letter, "Sniffing Out Pain."1-2 In Part I, "Olfaction's Complex Connections of Emotions, Memory, and Pain Perception," I explained how the sense of smell can induce powerful affective experiences due to the intricate neuroanatomy of olfaction.3-4 Unlike other senses, smell has reciprocal axonal connections with the primary emotion areas: the amygdala, hippocampus, and orbitofrontal cortex (OFC). This means olfactory stimulation can bypass the primary olfactory cortex and directly activate the amygdala at the secondary olfactory cortex.3-4
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How the brain determines and translates odors is individualized and extremely complex. The exact mechanisms of this still have not been fully elucidated.1 As a result, an aroma can alter emotional response, perception, and pain sensation based on an individual's past experiences of it.1-4 In fact, there is even evidence of epigenetic behavioral imprinting and physiological transmissions of emotions triggered by an odor based on an offspring's mother's prenatal association with it.1
In Part II, "The Multimodal Actions of Essential Oils on Pain Perception and Pain Relief," I provided evidence that essential oils' pleasant aromas are combined with their powerful secondary metabolites to entice a simultaneous physiological and psychological relaxation response as they modify pain perception. They have been shown in clinical trials to alter pain acuity by modulating one's emotional response and nervous system tone. Furthermore, in vivo and clinical trials have reported specific actions of certain essential oils and their constituents on cellular receptors for nociception. Due to their biochemical profile, and the influence of manufacturing practices on the presence and integrity of these delicate constituents, it is imperative to use quality, therapeutic essential oils for these desired therapeutic outcomes.2
I have been requested to write a follow up to these articles on the "nitty gritty" of putting this knowledge of essential oils to clinical use. With any medical intervention, physicians in training must first build on basic principles and understand contradictions, precautions, and side effects to be competent in prescribing and avoid harm.
Due to the complexity and caveats that exist about essential oils, I have divided the present article into segments and have narrowed my focus to their internal application for intestinal pain. This is because ingestion is the most controversial and misunderstood topic within aromatherapy and gastrointestinal concerns are common in integrative medicine practices, even if not the chief complaint. This also has been the area I see rapid, consistent results in my GI clients over the past eleven years.
First, I provide an overview of essential oils, including modes of application; details on liver biotransformation, metabolism, and excretion throughout the body; medication interactions; and the controversies and inconsistencies regarding various subtopics in aromatherapy.
Next, I review all the considerations for oral administration of selected essential oils for intestinal discomfort. In this portion, I discuss what the research states about their mechanisms of actions (including their effects on the microbiome) and dosages reported in clinical trials, if available.
I have also included a table that can be used as a dilution guide and for conversions of measurements to accurately dose essential oils. It is applicable for all modes of administration. Finally, I provide insight on how I use them with my clients.
After understanding all the complexities of prescribing essential oils using this example, doctors can apply this knowledge and find information for selecting specific essential oils for other areas of pain relief within Part II of my first series.
The Art and Science of Aromatherapy- Considerations, Caveats, and Controversies
Precise dosages, applications, and safe use of essential oils are unfamiliar to many practitioners. To complicate matters, they are also controversial among aromatherapists trained in different schools of applications. This is due to differences in training and licensing requirements for aromatherapy certifications. 5-9
Currently, there is no international standardization for aromatherapists. The National Association for Holistic Aromatherapy and Alliance of International Aromatherapists are two well-known professional organizations.5-8
To compound matters of confusion, there have been several misleading headlines in the media on the actions of essential oils.10-13 These have often been based on extrapolations from in vitro or in vivo studies that assess only one or two constituents that are found within them. These same experiments also often dose at much higher levels than would be administered therapeutically of an essential oil.10-26
This has led many busy physicians and intelligent scientists to falsely equate the same mechanism of action of an essential oil's isolated compounds to the oil itself. Unfortunately, these assumptions have resulted in physicians believing that some essential oils are risky and unsafe for their patients.10-14 The most recent flashy lead story, "Will Essential Oils Like Lavender and Tea Tree Make Your Breasts Larger?" is an example of this hype.11
Below are evidence-based reasons why one should remove these biases and not make this error of comparison. Rather, one should consider the synergistic effects of an essential oil, which is comprised of hundreds of different compounds and their total effect in humans,15-26 not a single component's effect in petri dishes or rats.
- Petri dish studies have been inconclusive in outcomes16 and have questionable validity due to the use of plasticizers, which can interfere with the test results.15-16, 20-21
- Toxicology reports are often based on in vivo studies using isolated compounds and nonapplicable methods of administration for humans (e.g., gastric lavage). Furthermore, rodents' metabolism of various substances differs from people.17-19,23
- The property of synergism of essential oils modulates the actions of all the compounds present and may impact a human's metabolome in individualized ways.24-26
It is imperative that one understands these points when considering the use of essential oils to real world applications.
Factors Related to Safe Use of Essential Oils
The three most common and routine routes of administration include the following:
- Inhalation, including direct inhalation, palm inhalation, diffusion, steam inhalation, and spritzers;
- Topical application, including massage, body oil, lotions, creams, baths, and use in dressings; and
- Ingestion (oral).5,7-9
Other applications, rectal and intravenous, have been reported in the literature. These are not often used or recommended by most schools of aromatherapy.27-28
Whichever method used, safety is always the first consideration. This is based on several factors. According to the National Association for Holistic Aromatherapy (NAHA), these are quality, quantity, chemical composition of the oil, integrity of the skin, and age of the individual.29
I believe that the safe application method and dosage of essential oils should also be based on the user's knowledge, experience, preference, and comfort level. It is also important to consider the essential oil being prescribed and the synergistic, epigenetic, and biotransformation properties of both the essential oil and the individual. Therefore, my additions to the list of safety factors include (1) understanding essential oil mechanisms of actions and their metabolism and (2) medication and lifestyle factors (epigenetics) that influence essential oils' effects.
Integrity of the skin and age of the individual are self-explanatory and should already be familiar with the practitioner. Although a full review of all these other factors is beyond the scope of the article, I will briefly touch upon them.
Quality and Standards
In discussing quality and standards of essential oils, it is important to denote the difference between them and risk association. For example, although the FDA regulates prescription drugs' standards and quality, even correct dosage can lead to medical errors, side effects, and various toxicities.30-35
For essential oils, the agencies of ISO (International Organization for Standardization) and the Association Française de Normalisation (AFNOR) are recognized by most aromatherapists for regulation, setting standards, and certifications. As with their standards across the market, those for essential oils are based on consensus and this means they have caveats and biases.38-41
ISO standards exist for approximately 50 essential oils.39,41 As noted on the ISO website: "ISO is an independent, non-governmental international organization with a membership of 161 national standards bodies. Through its members, it brings together experts to share knowledge and develop voluntary, consensus-based, market relevant International Standards that support innovation and provide solutions to global challenges."38
AFNOR is a member of ISO and develops their international standardization activities, information provision, certification, and training through a network of members of its own association.39-41 AFNOR also does not claim to seek to ensure quality in their recommendations.*
In an email exchange between myself and a chemist from a well-known essential oil company, it was explained to me that the ISO standards for essential oils were created, in most cases, because an AFNOR standard existed. He stated that if an ISO/AFNOR standard is met, it will probably be a high-quality oil; however, this is not always the case.*
These standards of essential oils are related to the relative percentage of certain constituents found within the essential oils that are deemed to be the most relevant for its effects. The values are usually determined from an analysis using a Gas Chromatology/Mass Spectrometry (GC/MS).36-44 This method does not distinguish between natural or synthetic constituents; therefore, it cannot determine if there has been "spiking" of these substances with manipulated compounds or adulterants to reach accepted standardized levels.42-44
The Caveats to Consider When Using GC/MS and Certificates of Analyses (CAs) to Verify Quality
Essential oil marketers may claim superiority of their essential oils based on GC/MC analysis and their verifications of analysis (CAs) that match ISO/AFNOR standards. Not being aware of the factors regarding GC/MS with essential oils, practitioners may make the false assumption that a CA for an essential oil provides a similar assurance of quality as their favorite brand of nutraceuticals.
Below is a summary of considerations regarding CAs of essential oils that highlights why relying on them to determine quality is incomplete.
- Not all essential oil manufacturers agree on the standardized percentage of active constituents to achieve therapeutic benefits. Therefore, a physician must be aware of the effects they wish to deem from the selected essential oil and its chemotype. These various populations within the same species produce differing plant secondary metabolites with distinct effects.2
Oftentimes the genus and species will be labeled on the bottle and its "active" compounds are revealed in the product description. Otherwise, the chemotype is labeled as "ct" followed by the predominant constituent.
- As previously discussed, if a constituent is present on the CA, it does not ensure that it hasn't been adulterated or synthetically spiked to achieve the standardized level.
Other companies with different constituents present on a CA could still be producing high quality essential oils. I will review some verification testing that companies may use to determine quality in the next section.**
- Plants will produce different percentages of compounds based on external pressures, their environment, the season, temperature, and climate. This means that there will be natural variations of components within the same chemotypes of essential oils. These cyclical changes in amounts of constituents on CAs does not necessarily indicate manipulation and adulteration of essential components.45-47 Conversely, they are often a welcome pattern.
- Unavailability of CAs of competitor brands of essential oils does not necessarily mean that they are "hiding something." Rather, they may be "protecting something." Legalities regarding propriety blends and differing quality standards of several popular essential oil companies is making it more difficult to obtain some CAs.
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