Essential Oil Quality, Standards, and Safety Part 3: Verifying Quality, Certificates of Analysis, Sourcing, and Purity from Plant Source to the Label

Finding “Quality Essential Oils”

Finding high-quality essential oils can be challenging due to varying opinions on preferred brands and the absence of governmental regulation on purity standards for aromatherapy. Recently, I started a series to help clarify this confusion for both new and experienced users.

Part I reviewed:

• The various factors that impact the selection of essential oil brands, including individual values, company reputation, price, community engagement, and marketing strategies.
• My goal to remain brand neutral and focus on the scientific aspects of essential oils to reach a broader audience, without the distraction of selling, marketing, or introducing biases.
• Research on essential oils aims to standardize compounds based on their biological properties, yet it offers limited details regarding their quality and purity.

Part 2 covered the standards and regulations of essential oils. Key points included:

• Essential oils’ power, purity, and quality can be affected by their production, manufacturing, and distribution.
• In the U.S., essential oils are not regulated for standards, quality, or purity but are monitored by the FDA (Food and Drug Association) for label accuracy and adverse events.
• Standards set by key global organizations (ISO and AFNOR) require essential oils to have specific percentages of active constituents.
• Standardized essential oils may be mixed with synthetic fragrances and chemicals, therefore not guaranteeing high quality or purity.
• High quality or pure essential oils may not meet consensus standards for specific compounds.

Now, in Part 3, I conclude this series on selecting quality essential oils by discussing the key characteristics I consider and my vetting process, including:

• My initial considerations for choosing quality essential oils
• Ensuring quality control from seed to label
• Verification testing
• Certificates of Analysis and their limitations
• The safe applications of essential oils

As always, all the research links, references, and previous video blogs will be available in this accompanying article and in the resource section.

Let’s get started!

 

My Initial Search for Quality Essential Oils

When I first began my essential oils journey, I was very skeptical. At the time I was a pharmacy technician, and I was very weary of my mom’s “unregulated hippie herbs” and “plant juices.”

Wanting to discover if what she was touting and the “internet hype” was founded, I became curious and started researching. One of my first discoveries was the book, “The First International Symposium on Integrated Medical Aromatherapy in Grasse, France (March 21-22, 1998).”

This book contained various presentations from who I now understand to be impressive and esteemed essential oil experts. These included Pierre Franchomme and Daniel Penoel, M.D. It also discussed various quality control measures, including using certificates of analysis. These were one way to provide evidence of important constituents found in specific essential oils.

Other highlights within this text included:

• The complexity of determining the quality of an oil vs. identifying its compounds using gas chromatography
• Volatile contaminants have been found in essential oils from poor manufacturing
• Benzene (a potential carcinogenic compound) and contact allergens were present in various fragrances
• The chemical composition of essential oils varies with seasons, cropping type, location, and climate
• How topsoil affects components of essential oils

I was then given an opportunity to visit a premier company’s essential oil supplier’s farm, which I’ve since recently returned to. Based on my book knowledge, I was impressed with their organic farming, production, and their passion for purity.

This provided me with confidence that these oils were of high quality, prompting me to incorporate them into my clinic and for personal use. Later, I discovered I still had more aspects to consider regarding essential oil purity. Thankfully, the same producer fulfilled these as well.

 

Ensuring Quality Control from Start to Finish

Since this time, I have consistently been updating my knowledge on essential oil quality to ensure I’m still using the purest oils, free from synthetics and additives.

This means that in addition to examining the final product, I also assess the oil production method by asking the manufacturers about the following:

What is their sourcing process and raw materials?- Is the oil sourced from seeds that are organic, grown on pristine soil, and what is the global location of plant material?

What are their cultivation practices?- What are they and are they sustainable?

How do they monitor distillation time, temperature, pressure, and specs for each oil?- An oil’s chemical makeup varies with distillation time, and this can alter biological properties. (R) Shortcuts can speed up distillation time but may lead to poor-quality oils, prompting manufacturers to add fillers and synthetics to mimic the true oil’s makeup.

What are their verification tests?-More on this below.

Are they carefully bottled and labeled using state-of-the-art equipment?- This ensures that an essential oil’s potency and purity remain intact and the terpenes do not oxidize.

 

Verification Testing for Essential Oil Quality and Sourcing

Due to the complexity of essential oils, it’s important to use more than one verification test to ensure the final product is high quality and pure.

Here are some vital examples of tests to verify and identify quality essential oils and their components:

• Gas chromatography (GC)- identifies constituents using a temperature-controlled capillary column which separates mixtures into individual components.
• Mass spectrometry (MS)- identifies the various chemical components based on the mass-to-charge ratio of ions. (14)
• Flash Point– identifies fluids based on the lowest temperature at which vapors of a fluid will ignite.
• Optical Rotation– a measure of purity and chirality based on the angle by which the plane of linear polarized light is rotated when passing through the sample. This helps determine if the substance is natural or synthetic. (15)
• Refractive Index– a dimensionless number that describes how light propagates through that medium.
• Specific Gravity– the ratio of the density of a substance to the density of a reference substance.
• Fourier transform infrared spectroscopy–creates a molecular fingerprint of the sample via the molecular absorption and transmission.
• Contamination testing including:
  • Heavy metals analysis (which aren’t usually distilled)
  • Microbial contamination

 

A Few Words on Certificates of Analysis- Gas Chromatography/Mass Spectrometry (GC/MS)

A certificate of analysis (CA) is a document that details a product’s specifications and quality testing results. In regards to an essential oil, CAs will often include Gas Chromatography/Mass Spectrometry (GC/MS) results of the various molecules present and deemed important for that specific oil.

Unfortunately, it’s becoming harder these days to get an essential oil’s CA from some companies due to propriety claims and popularity. If you are able to obtain them, you will notice that they can vary greatly from vendor to vendor and from product to product.

I have discovered that GC/MS of essential oils have several caveats to consider, including:

• Standards do note equal quality: Not all essential oil manufacturers deem the same active constituents as important in their products. This means if a standardized constituent is present, it doesn’t ensure the source is pure. Furthermore, if the constituent is absent, it doesn’t mean the oil is not pure.
• Some essential oils are 100% sourced from a company’s own farms, trusted suppliers, or esteemed producers of them. These companies should disclose if testing was in-house and/or third party verified.
• Not all producers are honest regarding their results, sources, verification, or production. You have to do more digging than just viewing the website claims.
• Acceptable values for the composition of components that are found on GC/MS of essential oils usually contain a range to account for natural variations. This is helpful for several reasons:
  • Essential oils that reside in the plant are constantly changing their chemical composition. Temperature, time of year, and environmental shifts will affect the secondary metabolites produced and which compounds are more prominent. (1, 2, 3, 4, 5, 6) This helps the plant to adapt to its ever-changing internal and external conditions.
  • Variations, therefore, are a clue that the company is not trying to “spike the oil” with synthetics in order to have consistency. Rather, they are honoring how the constituents within essential oils change, according to the plants’ needs.

In summary, GC/MS CAs are not the guarantee of purity or quality some believe them to be, as they report on the constituents that are present, but not oil purity.

 

Safe Application Tips for Essential Oils

Now that we know how to find good quality oils, here’s some quick safety tips for how to use them.

• Essential oils can be applied topically, diluted with a carrier oil, and avoiding sensitive areas. Please see this chart and start with the lowest dilution ratio when applying oils to the skin. Use up to 2% for topical applications and you can increase dilution ratio to 5% or higher for acute issues, under supervision.
• You can also directly inhale essential oils from the bottle and diffuse them for their mind-body benefits.
• Some oils can be taken internally as needed. Please do not exceed 6 drops a day and only use internal ingestion of pure oils and under the care of an expert.

 

Summary on Verifying Quality and Purity of Essential Oils

We’ve covered a lot in our quest for quality essential oils. Here’s a summary of what we’ve learned in this section:

• Choosing high-quality essential oils requires research and asking manufacturers the right questions.
• To find pure oils, you must consider sourcing raw materials, verification, and quality assurance testing.
• A CA using GC/MS doesn’t guarantee an essential oils’ purity, as oils could contain synthetic constituents. (Standardization vs. quality and purity)
• Once you obtain pure essential oils, please make sure you are using them safely and mindfully.

I hope this information was helpful.

By working together to achieve high standards, accessibility, sustainability, safety, and better education of essential oils, all oilers can unite to be a powerful force for healing.

I look forward to hearing your comments and feedback.

Thank you so much for taking the time to learn how to nurture your mind, body, heart, and soul.

Sending you many blessings.

 

Interested in Learning More About Essential Oils?

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• Learn about the Parasympathetic Blend.
• My branded essential oils website
• Essential Oils DIY Recipe Group (Facebook)
• Take the Wyld Notes quiz to find your personalized, all-natural, non-toxic signature scent here. Click here for your 10% coupon code.

 

Resources

• Not All Essential Oils Are Equal (The English Aromatherapist)
• The Quality of Essential Oils (The School of Aromatic Medicine)
• Guide to Verifying Essential Oil Quality (AromaWeb)
• In Defense of Essential Oils: Synergy, Nature’s Wisdom, & Misleading Studies (My peer-reviewed article on NDNR)
• Why Do Consumers Prefer One Brand Over Another? The Economics and Sociology of Brand Competitiveness (Journal of Retailing and Consumer Services, May 2023.)
• Exploring the Complexities and Caveats of Safe Internal Use of Essential Oils for Pain: Highlighting Intestinal Discomfort, Part 1. (My peer-reviewed article originally published on Townsend Letter. Quality and Essential Oils Science)
• GetOiling Site (My branded essential oils website)
• The Many Benefits of Lavender Oil (My video article with scientific references, an example of essential oils studies)
• Essential Oils DIY Recipe Group
• A Personalized Diet Using a Naturopathic Medicine Approach to Nourishing the Body with Food (My article with references, biochemical individuality)
• Aromatherapy and Essential Oils: Holistic Strategies in Complementary and Alternative Medicine for Integral Wellbeing. (Plants (Basel). 2025 Jan 29;14(3):400.)