Essential Oil Adulteration
Estimates indicate that approximately 80% of the essential oils that are commercially available have undergone some form of adulteration according to Robert Pappas, PhD and Prabodh Satyal, PhD.1
Adam Christensen, of Essential Validation Services has reported that France exports twice as much Lavender Essential Oil, India exports twice as much Peppermint Essential Oil and China exports a whopping ten times as much Tea Tree Essential oil as they produce every year.2
How Can More Essential Oil Be Exported Than is Actually Produced?
With steep competition and the limited supply of quality botanical material, it can be extremely tempting for distillers and producers to adulterate essential oils to increase the desirability or the yield of their essential oils.
I'll provide a more precise definition of adulteration below, but for this moment, think of adulteration as a way for unethical distillers and sellers to attempt to deceitfully pass off modified essential oils as being pure.
Why Does It Matter if an Essential Oil is Adulterated?
If an essential oil has been adulterated, it may still smell very much like a pure essential oil, but the composition has been modified, and the oil may not provide the therapeutic outcome that you are expecting.
Depending on how an essential oil was adulterated, the essential oil may also pose safety or toxicity concerns. I elaborate on this later within this article.
Sadly, the widespread incentive and lack of culpability for intentional adulteration and careless contamination requires that consumers be especially careful when shopping for essential oils.
Familiarizing yourself with the different concepts and ways that essential oils are adulterated can be helpful in knowing what to watch for when selecting brands and shopping for essential oils. This can help you save a lot of money and discouragement.
Let's get started by taking a look at two important terms:
Essential Oil Adulteration vs. Contamination
Within the general scope of aromatherapy, we tend to speak more often of adulteration, but contamination is also a significant concern.
There is a gray area between the two concepts. Depending on who you talk to, the distinction between these terms can differ. However, adulteration and contamination can both corrupt an essential oil. They do so in varying ways, and the intentions behind the person(s) committing the adulteration vs. contamination can differ.
Both adulteration and contamination can occur out of carelessness or ignorance of those harvesting and distilling the plant material or selling the essential oil. This can occur without conscious intent to deceive the buyer.
Many cases of adulteration, however, are done intentionally with the intent to defraud the buyer.
This guide focuses primarily upon adulteration as this tends to be the most intentionally insidious method of corrupting essential oils. Where applicable, I do discuss common ways that essential oils can become contaminated.
Let's move on by taking a deeper look at the typical definition of both concepts:
Definitions of Adulteration and Contamination
Later on within this guide, I'll dive into some of the different ways that essential oils are adulterated or become contaminated.
Are All Forms of Adulteration Considered Bad?
Using the above definition of adulteration, then yes, all forms of adulteration are bad as this act corrupts the resulting substance or makes it inferior. To me, an implied part of the definition is that the changes made to the substance are intended to primarily benefit the adulterator, not the purchaser of the essential oil.
However, some intentional modifications to essential oils are intended to directly benefit the purchaser and are fully disclosed by reputable producers and sellers. This does modify the pure essential oil, but it does not corrupt the oil at the expense of the purchaser and thus doesn't perfectly fit my interpretation of the definition of adulteration.
Cold pressed Bergamot Essential Oil that has been rectified to remove the Bergapten, is a good example.
Bergapten is a furocoumarin naturally present in cold pressed Bergamot Essential Oil. Bergapten is highly phototoxic. When using Bergamot Essential Oil that has not had the Bergapten removed, Tisserand and Young recommend a dermal maximum use of 0.4% to avoid phototoxicity. That is less than half a percent.
Otherwise, application of any leave-on product that exceeds this miniscule amount of Bergamot Oil runs the risk of causing severe phototoxic reactions such as burning, blistering and skin pigmentation changes.
Therefore, it can be much safer to purchase Bergamot Essential Oil that has the Bergapten removed, sometimes known as furocoumarin-free (FCF) Bergamot. It's always important to make absolutely sure to know what type of Bergamot Essential Oil you are using, especially for topical applications.
Types of Adulteration
Wrong Plant Species Included in the Distillation of the Essential Oil
It is estimated that there are approximately 350,000-390,000 plant species known.3, 4 Just imagine how many plants look similar to each other and how easy it can be for two species to be accidentally confused for one another. Some may also intentionally attempt to pass one species off as another.
Some plant species look similar to others but have different therapeutic properties, applications and safety precautions. They also can have very different market prices. There is sometimes a risk that those overseeing cultivation or those wild harvesting botanical material may accidentally mistake one species for a similar looking species. The entire crop or harvest could potentially contain the mistaken species, or could be a mix of multiple species.
As I'll discuss further down in this guide, several species of lavender are grown and distilled for their essential oil, and the different lavender species can sometimes be mistaken for one another.
Using Parts of the Plant That Aren't Disclosed
Sadly for consumers, there is an incentive by some distillers to include more abundant parts of a plant in a distillation to achieve a higher yield without disclosing this to the customer.
The specific part(s) of a plant that are distilled play a direct role in the aroma, efficacy and safety considerations of the finished essential oil. This is why it is important to not only pay attention to the botanical name of the plant that an essential oil is made from, but it's also important to pay attention to the part(s) of that plant that was used in the distillation.
For example, if an essential oil is labeled as Neroli (Orange Blossoms), but an excessive amount of twigs and branches were included in the distillation, this can impact the market value, composition and aroma of the resulting oil. The resulting oil may be what is considered a very beautiful neroli/petitgrain co-distillation, but it should not be labeled as a true Neroli Oil and it should not command the same high price.
Petitgrain Oil is the common name given to essential oil that is steam distilled from the leaves and twigs of the bitter orange tree (the tree that also gives us Neroli Oil), and it is far less expensive than Neroli Oil. I find Petitgrain to be a hidden gem and use it often, but a pure Neroli Essential Oil should not include leaves and twigs in its distillation. I should clarify that some twigs and leaves can get into the distillation of Neroli Essential Oil, but I have smelled some Neroli Essential Oils that clearly smell more like a co-distillation of the blossoms (Neroli) and twigs/leaves (Petitgrain) and that are probably not true Neroli essential oils.
Mislabeled or Misrepresented Botanical Name of Essential Oil
Let's take a look at the most common Lavandula essential oils that are readily available:
- Lavender also sometimes known as True Lavender: Lavandula angustifolia / Lavandula officinalis
- Lavandin: Lavandula intermedia / Lavandula hybrida
- Spike Lavender: Lavandula latifolia
Lavandin (Lavandula intermedia / Lavandula hybrida) is a hybrid of True Lavender (Lavandula angustifolia / Lavandula officinalis) and Spike Lavender (Lavandula latifolia).
Lavandin Essential Oil has a higher yield than True Lavender Essential Oil and generally commands a cheaper price. (Having said that, I have purchased beautiful artisan Lavandin Essential Oils that are worth more than poorly distilled True Lavender Essential Oils, so my comments are intended as a general reference).
Sometimes, Lavandin is combined with True Lavender in order to obtain a higher price. Sometimes similar species are collected, harvested and co-distilled and customers are told the essential oil is of a single botanical.
Fragrance Oils Mislabeled as Essential Oils
Fragrance Oils are not the same thing as Essential Oils. However, there have been cases where unscrupulous or clueless sellers have mislabeled and sold Fragrance Oils as Essential Oils.
Adding Lesser Expensive Substances or Constituents to Essential Oils to Improve the Aroma or to Increase the Yield
Essential Oils are naturally comprised of many aromatic molecules that we often refer to interchangeably as essential oil constituents. Many essential oils contain over 100 different types of aromatic molecules. However, each essential oil contains certain key constituents that are noteworthy from an aromatic and/or therapeutic standpoint.
Without getting too technical, some aromatic constituents can be cheaply synthesized in a lab or by using fractionation to separate them out of lesser expensive essential oils. Lavender Essential Oil, for example, can be adulterated by adding linalol or linalyl acetate to increase the volume and improve the perceived desirability of the resulting oil. This issue is one of the most insidious forms of adulteration and happens often within the essential oil industry.
Constituents and substances that are typically added to adulterate essential oils include the following5,6,7,8:
- Carrier Oil
- Synthetics (i.e. Phthalates)
- Natural Isolates (i.e. Terpenes)
- Synthetic Compounds (i.e. Synthetic Linalol, Linalyl Acetate)
- High Boiling Glycols
Essential Oils at Highest Risk for Adulteration
Any essential oil has the possibility of being adulterated, but these are the circumstances that increase the likelihood of adulteration9:
- Essential oils that originate from plants that generate the lowest essential oil yields
- Essential oils that command the highest market prices
- Essential oils that originate from plants that are classified as Vulnerable, Endangered or Critically Endangered by the International Union for Conservation of Nature (IUCN).
Even Sweet Orange Essential Oil, which tends to be one of the most inexpensive of essential oils, has been found to be adulterated.
Types of Contamination
Packaging Essential Oils in Dirty Bottles or Drums that Previously Stored Something Else
If a distiller or supplier reuses their containers without properly cleaning and sanitizing them, any remaining substance or residue left inside the container can contaminate the new oil put into the container10.
Mixing Batches of Essential Oils
Some suppliers mix lots of essential oils distilled from the same or similar botanical material for varying reasons. Sometimes this happens unintentionally, but it can often be intentional11.
Storage In Inferior Packaging Materials
Undiluted essential oils are highly concentrated and can break down some forms of containers. Chemicals from the unapproved containers can leech into the essential oil, contaminating it.
Selling Poorly Stored or Aging Essential Oils
Essential oils that have been stored in hot conditions or with exposure to sunlight can experience degradation much faster than oils stored in optimal conditions. Additionally, essential oils oxidize over time. As oils age and oxidize, the composition, aroma, therapeutic benefit and safety of an essential oil generally diminishes even in optimal storage conditions.12
Other Forms of Essential Oil Modification By Distillers and Suppliers
Some classify standardization and rectification as forms of adulteration. However, these methods are generally disclosed to the buyer.
I am mentioning standardization and rectification within this article to help address any potential underlying questions that may arise. However, these processes don't necessarily fall under the umbrella of deceptive adulteration if the intent is to benefit the buyer and if the modifications are clearly disclosed to the buyer.
Maria Lis-Balchin explains Standardization this way:
"The ISO (International Organization for Standardization) is responsible for setting the standard composition for each essential oil, which has to be adhered to. The ISO may therefore indirectly be responsible for some of the blending, if not adulteration of essential oils in order to keep within their guidelines. Bearing in mind the natural variability of harvests, blending of essential oils from different harvests often occurs, as with wines. There is also the opportunity for the more unscrupulous producers to add some synthetic components or fractions from different plant oils."13
A few essential oils are intentionally rectified to eliminate undesirable or toxic components. Reputable sellers should confirm when an essential oil has been rectified. Robert Tisserand concisely explains the process of rectification as follows:
Rectification involves fractional distillation in order to remove unwanted constituents. The essential oil is put through a second process using a tall, narrow column.14
How is Essential Oil Adulteration and Contamination Detected?
In some instances, the color, texture and aroma of an essential oil can be an indicator that an essential oil may be adulterated. Assessing an essential oil's physical characteristics is known as organoleptic testing.
However, the majority of adulterated essential oils are done in a way that makes it very difficult, even for professionals, to be able to determine that they are adulterated or contaminated by observing only their color, texture and aroma.
Gas Chromatography and Mass Spectrometry (GC/MS)
The most reliable present-day method for testing essential oils is conducted by Gas Chromatography and Mass Spectrometry (GC/MS). GC/MS testing is an excellent tool for assessing the composition and integrity of most essential oils. However, some expert adulterations can still be missed by GC/MS testing, particularly if the testing is done by technicians that lack adequate expertise in testing essential oils.15
Other Testing Methods
Refractive Index, Specific Gravity and Optical Rotation are other tests that can also help detect some forms of essential oil adulteration and contamination. They are typically done in tandem with GC/MS testing.
Is the Quality and Purity of Essential Oil Truly Important?
Absolutely. It is important for ensuring that you achieve the expected outcome that you seek from the essential oil, but it also ensures that you are supporting ethical and responsible distillers and suppliers.
I like how the Australian Tea Tree Industry Association (ATTIA) explained the concerns. Their concerns are specific to Tea Tree Essential Oil, but many of these same concerns are applicable to other essential oils:
"These adulterated or synthetic products masquerade as TTO [Tea Tree Essential Oil] and have no scientific evidence to support their safety and effectiveness. Furthermore, they are not supported by the thousands of years of use by the Australian Aboriginal indigenous population. Synthetically produced oils may be placing consumers at risk. At the very least, it may turn many consumers away from using tea tree oil entirely. The fraudulent use of adulterated and "nature identical" oil is unethical and potentially deprives users of the right to use an essential oil proven to work safely and effectively. Growers are disadvantaged by the practice as the cost of bringing these adulterated or synthetic products to market is significantly less than the cost an Australian farmer can sustainably produce genuine pure Australian TTO."16
For more information, see the Why Is the Quality and Purity of an Essential Oil Important? article that is a part of AromaWeb's Guide to Verifying Essential Oil Quality.
What Does All This Mean for Consumers?
As mentioned above, the widespread incentive and lack of culpability for intentional adulteration and careless contamination requires that consumers be especially careful when shopping for essential oils.
Even if an essential oil smells wonderful to you, that doesn't necessarily mean that the essential oil will provide the therapeutic outcome that you are expecting.
Steps to Minimize the Risk of Purchasing Adulterated Essential Oils
- As tempting as it is, be very careful to not purchase essential oils based on price alone. Cheap essential oils aren't always a better value.
- Refer to AromaWeb's What to Look for and What to Watch Out for When Shopping for Essential Oils article for a list of 20 valuable tips that can help you compare essential oil brands and sellers.
- More and more reputable essential oil brands are having their essential oil independently GC/MS tested and are including the test results on their websites.
- GC/MS testing can cost suppliers around $150-$200 US per analysis. Keep in mind that this isn't cheap for essential oil suppliers, and can be reflected in a slightly higher cost for essential oils sourced from companies that provide independent testing results.
- The most reliable GC tests are those that have maintained a careful chain of custody and that are done independently, meaning that the brand sent their oil to a third party testing company such as Essential Validation Services in the United States or Phytochemia in Canada for analysis. Pay attention to the reports and use them to help you making your purchasing decisions.
- Many of AromaWeb's advertisers make their GC/MS reports available directly on their websites or provide them upon request. Although AromaWeb cannot endorse any company or the purity of every single essential oil they sell, AromaWeb's advertisers are a wonderful starting point when shopping for essential oils.
1Robert Pappas, PhD and Prabodh Satyal, PhD, Adulteration Analysis in Essential Oils, 2016. (The International Journal of Professional Holistic Aromatherapy, Volume 5, Issue 2), 33.
2Adam Christensen, Conference Presentation: The Chemistry of Essential Oil Adulteration: How, Why, and What You Need to Know. May, 2018, Atlanta, GA. Handcrafted Soap and Cosmetics Guild Conference, Presentation PDF, 1.
3World Flora Online Website. Accessed: September 7, 2020.
4Plants and Policy: Tacklin Global Challenges, Royal Botanic Gardens Kew. Accessed: September 7, 2020.
5Erich Schmidt and Jurgen Wanner, Essential Oil Adulteration. Handbook of Essential Oils (Second Edition. New York, NY: CRC Press, 2016, 717-720.
6Christensen, Presentation PDF, 5-6.
7Robert Tisserand and Rodney Young, Essential Oil Safety (Second Edition. United Kingdom: Churchill Livingstone Elsevier, 2014), 7-10.
8Salvatore Battaglia, The Complete Guide to Aromatherapy Third Edition Volume 1 - Foundations & Materia Medica (Brisbane Australia: Black Pepper Creative, 2018), 78-81.
9Tisserand and Young, Essential Oil Safety, 9.
10Christensen, Presentation PDF, 2.
12Erich Schmidt and Jurgen Wanner, Essential Oil Adulteration, 716.
13Maria Lis-Balchin, Aromatherapy Science: A Guide for Healthcare Professionals (United Kingdom: Pharmaceutical Press, 2006), 39.
14Blog Post: "Is There Such a Thing as Re-distilled Peppermint Oil?" (Robert Tisserand, 2014). Accessed: September 7, 2020.
15Rodolfo Juliani, PhD and Rutgers Faculty. Workshop: Guide to Quality Control of Essential Oils from the Field and Forest to the Bottle. Alliance of International Aromatherapists Conference, New Brunswick, NJ, 2017.
16Quality and Adulteration, Australian Tea Tree Industry Association (ATTIA). Accessed: September 7, 2020. [The original link no longer works, so I've provided a link to the article via Archive.org.]