How to Choose High-Quality Essential Oils?

With essential oils growing in popularity, it’s easier than ever to buy them. But much harder to know if you’re getting a truly high-quality product. For those starting their aromatherapy journey, understanding quality is key to using essential oils safely and effectively.

At Essence of Thyme College of Holistic Studies, we believe that education is the foundation of confident, ethical practice. Here are five essential tips, grounded in professional-level aromatherapy knowledge, to help you assess essential oil quality like a pro.

1. Check the Label for Key Information

A good essential oil label should be transparent and informative. Unfortunately, many commercial oils are labelled in vague or misleading ways, which can confuse even the most well-intentioned beginners.

Here’s what a high-quality label should include:

• The Latin botanical name (e.g., Lavandula angustifolia) is a universal naming system that identifies a plant species, which is essential in a world where common names like “sage” may refer to very different plants. Learn more about essential oil terminology here.
• The part of the plant used (e.g., flower, leaf, bark, resin) which is the source of an essential oil will differ in chemistry, aroma, and safety. For example, cinnamon bark and cinnamon leaf oils come from the same plant (Cinnamomum zeylanicum), but their properties differ. Read more in this article.
• The method of extraction (e.g., steam distilled, expressed) determines both the composition and safety of an oil. For example, expressed bergamot contains bergapten, which can cause phototoxic reactions. Some suppliers offer bergamot FCF (furanocoumarin-free), which is safer for skin use.
• The country or region of origin can affect the oil’s chemistry through soil, altitude, and climate. For instance, high-altitude true lavender (Lavandula angustifolia) often contains more relaxing esters. Regional context also supports sustainability, especially when traditional, small-scale distillers are involved.
• A batch number or distillation date allows traceability and reveals the oil’s freshness and seasonal profile. Just like wine, factors like rainfall and harvest timing affect quality. Responsible suppliers rotate stock and provide batch-specific details for transparency and safety.

You should also be able to determine whether the oil is wildcrafted, organically grown, or certified organic. This speaks not only to quality but also to ethics and sustainability.

Avoid products labelled simply as “lavender oil” or “100% pure essential oil” without further details. These are often fragrance oils, which may contain synthetic ingredients, diluents, or adulterants. Even if a bottle says “natural,” that doesn’t guarantee purity or quality. 

Tip: If you’re shopping online and the product description or label photo doesn’t include this information, that’s a red flag. Quality suppliers want you to be informed.

2. Know the Source: Organic, Wildcrafted, or Certified

Where and how a plant is grown has a direct impact on the quality, safety, and sustainability of the essential oil . As an aromatherapy student or practitioner, understanding sourcing terminology empowers you to choose oils that align with your values, and deliver true therapeutic benefit.

The three common sourcing types to look for:

• Certified Organic – These oils are derived from plants grown without the use of synthetic pesticides, herbicides, or fertilizers. Certified farms follow strict agricultural practices and undergo regular inspections to ensure compliance. These oils tend to be more expensive, but many aromatherapists believe they carry greater energetic vitality and a reduced risk of pesticide residue.
• Wildcrafted – These oils are sourced directly from plants growing in their natural, wild habitat, where they’ve likely never been exposed to agricultural chemicals. Wildcrafted oils are often deeply aromatic and complex, but their use also demands conscious conservation. Not all wild harvesting is sustainable and regenerative, so it’s important to ask how and where the plant material was collected.
• Non-Certified Organic – These oils come from plants that were grown using organic methods, but without formal certification. Certification can be costly, especially for small-scale or traditional farmers. Non-certified organic oils are often excellent in quality, especially when sourced from trusted distillers who use ethical growing and harvesting practices.

At Essence of Thyme College of Holistic Studies, we teach our students to look beyond just the label and consider the story behind the oil, its soil, climate, cultivation and harvesting practices. Choosing oils with care supports not just your health, but also ecosystems, farmers, and future generations.

“The conservation of aromatic plants is critical to the future of aromatherapy. Responsible sourcing ensures not only quality, but long-term access to these precious botanicals.”

— Dr. Kelly Ablard, Essence of Thyme College’s Co-Principal, conservation biologist and aromatherapy educator.

3. Understand Adulteration and Why It Matters

One of the biggest quality concerns in aromatherapy today is adulteration, which is the practice of altering an essential oil by adding, removing, or substituting components to increase volume, reduce cost, or standardize aroma. While this may benefit the supplier’s bottom line, it can seriously compromise the safety, effectiveness, and integrity of the oil.

Adulterated oils may contain:

• Cheaper essential oils mixed in to “stretch” volume
• Synthetic aroma chemicals added to mimic scent
• Carrier oils or alcohol added to dilute the product
• Nature-identical compounds that smell similar but lack therapeutic complexity
• Or in some cases, the oil may be entirely synthetic and falsely labelled as “natural”

This kind of tampering isn’t always easy to detect with the naked eye, or even by smell, especially for beginners. However, over time, trained aromatherapists develop the ability to evaluate oils using organoleptic testing, which includes assessing the oil’s aroma, appearance, and texture.

What can you do as a beginner?

• Ask for transparency. Reputable suppliers should be willing to share Gas Chromatography–Mass Spectrometry (GC-MS) test results, which reveal the oil’s chemical composition. These reports help confirm authenticity, especially when interpreted by someone trained in essential oil chemistry.
• However, small-scale or artisan producers may not be able to test every batch due to cost. In such cases, look for other signs of integrity: clear sourcing information, ethical harvest practices, honest communication, and a consistent track record of quality. A transparent supplier can still be trustworthy, even without constant lab testing.
• Be especially cautious with rare or costly oils like rose, frankincense, sandalwood, neroli, or melissa (lemon balm). These are often targets for adulteration due to high demand and limited availability.

• Use your senses wisely. Pay attention to how an oil smells, feels, and behaves. If it has an overly sharp or artificial scent, feels greasy, or looks cloudy (when it shouldn't), it may be adulterated. With time, you’ll develop your own sensory intuition, which is an invaluable skill in aromatherapy.

Important: At home tests like the blotting paper or water-glass test may seem appealing, but they are unreliable and can give false positives, especially for oils that are naturally colored, viscous, or slow to evaporate.

Ultimately, learning to recognize adulteration is part of becoming a skilled aromatherapist. That’s why we teach our students not just to use essential oils, but to understand them on a deeper level, through science, practice, and sensory experience.

4. Watch Out for Oxidation

Even the highest-quality essential oil can lose its value, and even become hazardous, if it’s not stored correctly. One of the most common issues is oxidation, a process in which oxygen reacts with the oil’s chemical compounds, changing its composition over time.

Oxidation is especially common in oils that are rich in monoterpenes, such as expressed  citrus peel oils (e.g., lemon, orange, and grapefruit) and conifer oils (e.g., pine and fir). As these oils degrade, they lose their therapeutic properties and may become skin irritants or sensitizers, even if they were originally safe to use.

Heat and light also accelerate oxidation, making proper storage essential for preserving both safety and effectiveness.

Smart storage tips:

• Keep oils in dark glass bottles to protect them from light
• Store them in a cool, dry place, away from heat sources
• Tightly seal bottles after each use to limit oxygen exposure
• Consider refrigerating oils prone to quick oxidation—like expressed citrus peel oils—to extend shelf life

Example from research: Expressed lemon peel oil stored at 25 °C (77 °F) with the cap removed daily showed a drop in d-limonene from 67.1% to 30.7% in just 12 months—alongside an increase in irritant compounds (Sawamura et al., 2004). This highlights just how quickly essential oils can degrade under poor storage conditions.

5. Beware of “Therapeutic Grade” Claims

If you’ve spent any time browsing essential oils online or in stores, you’ve probably seen phrases such as “therapeutic grade” or “certified grade” used to suggest superior quality. However, it's important to understand that this term is not regulated by any governing body, and it’s purely a marketing phrase. There is no official organization that certifies essential oils as “therapeutic grade.”

While it might sound reassuring, the phrase doesn't guarantee purity, ethical management, or authenticity. What truly matters is how the essential oil-bearing plant was grown, harvested, distilled, and handled, and whether the supplier is transparent about testing, sourcing, and sustainability.

At Essence of Thyme College of Holistic Studies, we teach students to look past flashy marketing claims and instead build a foundation of knowledge based on botany, chemistry, sustainability, and real-world application.

“Aromatherapy is not just about using oils—it’s about understanding them. Education gives you the confidence to choose wisely and use oils effectively.”

— Colleen Thompson, Co-Principal and Founder of Essence of Thyme College

Ready to Go Deeper?

Choosing quality essential oils doesn’t have to feel overwhelming. With the right guidance, you can move beyond marketing hype and confidently select oils that are safe, effective, and ethically sourced. At Essence of Thyme College of Holistic Studies, we believe that education is empowerment, and that understanding your oils is just as important as using them.

Whether you're exploring aromatherapy for personal wellness or considering a professional path, we’re here to support you every step of the way. Explore our Professional Level Aromatherapy Certification to take your knowledge to the next level, or download our free Essential Oil Safety Guide below to start your journey with confidence.

Download your Essential Oils Safety Guide!

No matter where you're starting from, you're welcome here. And we’re excited to help you grow from curious beginner to confident practitioner, rooted in knowledge, grounded in ethics, and inspired by the beauty of the plants themselves.

References

Sawamura, M., Son, U.-S., Choi, H.-S., Kim, M.-S. L., Phi, N. T. L., Fears, M., & Kumagai, C. (2004). Compositional changes in commercial lemon essential oil for aromatherapy. International Journal of Aromatherapy, 14(1), 27–36. https://doi.org/10.1016/j.ijat.2004.02.001 

Article by: Essence of Thyme College of Holistic Studies

About Essence of Thyme College of Holistic Studies

Essence of Thyme College of Holistic Studies offers 300- and 630-hour professional aromatherapy certification programs that help you grow a successful, fulfilling career by specializing and creating your market niche. Professional Level Certification prepares graduates to become aromatherapy consultants, launch product lines or retail businesses, or provide services as an adjunct to existing holistic health specializations. Master Level Certification and electives are ideal for certified aromatherapists seeking higher education or a path to clinical aromatherapy practice.

All Essence of Thyme programs focus on aromatherapy product development and advanced formulation, evidence-based research, spa and business management, international industry regulatory guidelines, and sustainability and conservation of essential oil and carrier oil-bearing plants.

Our comprehensive, evidence-based programs meet or exceed the criteria set forth by 5 international professional aromatherapy associations. Learn more about our aromatherapy certification programs.