What Are Essential Oils?

A variety of plants cover the Earth in different shapes, sizes, colors, and scents. Many of these plants contain compounds that typically can’t be seen with the naked eye—they hide within the roots, flowers, seeds, bark, or other areas of the plant. These compounds are known as essential oils.

They are highly concentrated, making them extremely potent. Also referred to as volatile aromatic compounds, essential oils give a plant its aroma, protect it from harsh environmental conditions and insects, and even play a part in plant pollination.

The Science Behind Essential Oils

When you hear the word “volatile,” you may think it holds a negative connotation; however, in the case of essential oils, volatility refers to a substance’s ability to change its state quickly. The chemical makeup of volatile aromatic compounds in essential oils allow them to disperse quickly through the air. This is why you can instantly smell the potent aroma of an essential oil from the moment you open the bottle—even from a distance.

How do Essential Oils Work?

As volatile aromatic compounds move quickly through the air, you will experience the scent when the compounds interact directly with sensors in the brain. With over 3,000 types of volatile aromatic compounds discovered so far, it is important to note that these compounds greatly determine the benefit, aroma, and nature of each essential oil. Because of unique chemical makeup, each essential oil will vary from species to species, and even from plant to plant. The delicate ratio of aromatic constituents found in any given essential oil are what make it unique and give it specific benefits. 

Essential Oil Use Throughout History

While some view essential oils as a new trend, the use of plant extracts and plant-based products is deeply rooted in traditions of the past. Ancient civilizations used plants for things like aromatherapy, personal care, health care practices, religious ceremonies, beauty treatments, and food preparation.

How Were Essential Oils Used Anciently?

Essential oil use is not a fad, but rather a long-time tradition started centuries ago in civilizations all over the world.

Essential Oils in History
  • Egypt: The use of plant-based products has been recorded as far back as 3000 BCE with the Egyptians, who used plant extracts for a myriad of purposes. They used them for beauty treatments, food preparations, burial rituals, and in religious ceremonies. Precious plant compounds such as peppercorns, cinnamon bark, frankincense, and myrrh fed the thriving trade routes that snaked through the arid deserts of the region.

    The reverence that this ancient culture had for plants is evident in the botanical depictions found in hieroglyphics and other Egyptian art. Modern archaeological techniques have also allowed researchers to identify residues of aromatic gums and resins in mummified bodies and at burial sites. When analyzing the mummy of Ramses V, an ancient Egyptian ruler, the aromatic compounds of juniper, camphor, and myrrh were discovered, confirming their usage in these sacred burial rituals.
  • Greece: Around 2000 BCE, the first civilizations in Europe were emerging in Greece, and with their development came an interest in perfumery and other plant-based treatments. The learned Greeks soon found themselves in Egypt to study medicine. Men like Homer (lived around 850 BCE), Hippocrates (460–370 BCE), Herodotus (484–425 BCE), and Plutarch (46–120 AD) took the traditions of the Egyptians and began to learn more about aromatics and plants. Their research permeated throughout Greek culture, influencing the practices of the time.

    The Greeks also worked on increasing the sophistication of extraction methods. There is written documentation of solvent extractions that used wine and fat mediums to pull the volatile compounds from plants.

  • Rome: In ancient Rome, aromatics were equally important in culture and health. The Romans were known for their scented baths, perfumery, and massages using plant extracts. The scientific literature discovered from this time period shows that plant extracts and aromatic compounds were widely used for their health benefits.

    Pliny the Elder (23–79 AD), Dioscorides (40–90 AD), and Galen (130–200 AD), well-known Roman scientists and physicians, all mentioned plant oils in their written works. Galen, an especially talented surgeon who relied extensively upon the teachings and methods of the Greek physician Hippocrates, used plant extracts during his work on the medical team at the Coliseum. There he performed surgeries on injured gladiators. Although many of his written works were tragically destroyed in a fire, his research influenced medicinal practices throughout Europe.

  • Iran: In medieval Persia (now known as Iran), many were similarly harnessing the power of plants. The people in this region regularly used and traded resins and spices that were prized for perfumery as well as maintaining health.

    Avicenna (980–1037 AD), a Persian doctor, wrote extensively on health and wellness and is credited as the father of aromatherapy as we now know it. He also left a lasting mark in the field of chemistry for his experimentation with distillation. He attempted various distillation methods using flowers and was eventually able to isolate the scent of the rose as well as produce rose water.

  • India: The term “Ayurveda” combines the Sanskrit words ayur (life) and veda (science or knowledge). The Ayurvedic tradition was developed in India over the course of 5,000 years and is one of the oldest systems in the world. In fact, many of the Ayurvedic practices precede written text and were passed down by word of mouth. Today, the majority of the people in India follow the Ayurvedic tradition exclusively or combine it with Western practices.

    The Ayurvedic practice stresses the use of the Earth’s elements to find balance in the body, and, in turn, good health. Ayurvedic physicians recommend individualized treatment plans that include the use of herbal mixtures. The original works describing this system and their protocols are still commonly used today. Although the methods vary widely, the Ayurvedic use of plant and aromatic compounds is currently taught in over 100 accredited universities in India. Emerging research is now being performed to validate many protocols rooted in this tradition.

  • China: Between 500 and 1300 AD, China was a leading world power with advances in science and technology that superseded any other civilization of the time. Traditional Chinese practices continue to be used to this day and still rely on the use of various plant materials for health and wellness. Legend takes us back to a man named Shennong, an emperor and teacher. Although legend tells us that Shennong understood the effects of plants due to having a transparent body that allowed him to ingest many different herbs and directly “see” how they affected his body, he also left behind texts describing his research on hundreds of different types of plants. Protocols based on his experiences and research have been passed down through generations to this day, and still exert influence on modern health care.

    Although the scientific advances made by China were long isolated from the rest of the world, eventually a stable trade route opened up between Europe and Asia. Perfumes, herbs, and spices were commonly traded along this route. Europe quickly became an epicenter of perfumery with scents from sandalwood, chamomile, sage, thyme, lemon, and clove regularly used during personal care regimens.

  • France: A major historical shift began in the 19th century when new developments in chemistry increased the sophistication and understanding of distillation methods. These advances led René Gattefossé (1881–1950), a French chemist and perfumist, to begin a more rigorous study of essential oils in research and practice. In fact, Gattefossé is credited as the first to coin the phrase “aromatherapy.” Medical doctors in France (and other areas around Europe) dispensed essential oils in their practice and to this day receive some training in medical school regarding their safety.

    The modern view of aromatherapy is evolving at a rapid pace as more research is being done on essential oils and their constituents. As technology continues to advance, extraction methods are improving and the many benefits of plant derivatives are becoming better understood. Traditional methods have certainly provided an excellent historical framework; however, much research is still needed to fully understand the massive potential of essential oils in managing wellness.

How are Essential Oils Made?

It is important to note that not all essential oils are created equal. The purity of an oil can change depending on geographic location, distillation methods, weather, and other factors.

Additionally, no matter how well a plant is selected, cared for, and harvested, the quality of an essential oil can either be preserved or destroyed during the distillation process. Because of the attention to detail and precision necessary in distillation, it becomes less of a process and more of an art form. Distillers must be precise and pay careful attention to:

  • Harvesting methods
  • Temperatures
  • Time of distillation
  • Amount of pressure used

How Does a Plant Become an Essential Oil?

The exact process for producing an essential oil will vary depending on what type of plant the oil comes from. However, the basic idea is that plants go through a specific distillation process using special machinery in order to separate the essential oil from its plant parts.

The essential oil hides within different parts of the plant, often in microscopic amounts. During the distillation process, the machinery will separate the essential oil from its original plant part. For example, when citrus oils are produced, machinery is used to separate the essential oil from the rind of the fruit.

doTERRA distillation

Essential Oils Today

While essential oils and plant extracts have been used for centuries, essential oils still hold relevant applications today. With advancing technology, improved quality, potency, and safety, essential oils are now more accessible and easy to use in everyday life.

Although essential oils were often used as a part of cultural practices and traditions of the past, we now have increasing scientific evidence and research to show the effectiveness and safe nature of essential oils in our day and age. 

Essential Oils for Health Benefits

In ancient times, people used essential oils and plant parts to improve their health and well-being because essential oils can be used to:

  • Soothe occasional skin irritations
  • Promote healthy digestion
  • Support good oral health
  • Create feelings of clear airways
  • Maintain good health

Essential oils offer a variety of benefits, and each individual experiences essential oil use in their own way. Fortunately, the diversity of essential oils makes them a helpful way to maintain health, even for those who have specific health concerns, seek diverse health benefits, or experience sensitivity.

Using essential oils for health benefits has become popular because it allows the user to tailor the experience to their specific wants and needs, rather than settling for a generic solution.

Essential Oil Health

The Emotional Benefits of Essential Oils

With unique chemical structures, each essential oil holds a variety of benefits for the user.

Some essential oils hold:

  • Soothing
  • Toning
  • Grounding properties

While others are known as

  • Energizing
  • Uplifting
  • Warming
  • Renewing.
As our bodies go through an array of emotions and physical states throughout a single day, essential oils can help us manage and maintain well-being. 

The chemical design of an essential oil gives it specific benefits.

Some essential oils are helpful for cleansing or purifying, while others provide a soothing sensation to the skin. The aroma of essential oils can also create a chemical reaction in the brain, eliciting emotions and internal responses. Our sense of smell can produce powerful, mental, physiologic, and emotional responses.

Essential Oil Quality

Certified Pure Therapeutic Grade Quality Testing

The purity of an essential oil is its most important characteristic. An essential oil that isn’t pure means you run the risk of putting germs, heavy metals, or adulterants onto or into your body, which can provoke irritation, adverse effects, or even sickness. Without an accepted standard for essential oil quality, doTERRA created its own testing process, calling it CPTG Certified Pure Therapeutic Grade.

The CPTG process certifies that there are no added fillers, synthetic ingredients, or harmful contaminants in their essential oils that would reduce their efficacy. doTERRA even goes a step further, putting all their products and the packaging through a battery of tests to ensure a long and effective shelf-life. This protocol ensures potency, purity, and consistency batch to batch.

Before the CPTG Process Begins

Proper methods of growing, harvesting, and distilling are also crucial to maintaining purity. Poor production practices and the development of synthetic essential oil variations suggest that it is impossible to accurately identify a pure essential oil without scientific analysis. Appropriate analysis of the constituents within an essential oil is one of the most challenging and detailed aspects of quality assurance.

Knowing which of the many different species of a given plant will provide the most profound therapeutic health benefits is the first step in producing the highest quality essential oil. Relying on the expertise of botanists, chemists and wellness practitioners, botanical materials are carefully selected for their natural concentrations of active aromatic compounds.

Nurturing plants in the most favorable environment and carefully harvesting and transporting plant material for processing ensures an optimal yield of pure and potent essential oils. Spanning the continents of the globe, doTERRA’s exclusive network of growers and harvesters are experts at cultivating plants specific to the essential oil industry.

The CPTG Process

The CPTG testing begins immediately after distillation with each oil being reviewed for its chemical composition. A second round of testing is carried out at our production facility to ensure that what was distilled and tested is the same essential oil as was received. A third review of the chemistry of the oil is conducted in a three-phase procedure as the oils are packaged into the bottles we use as consumers. Each of these tests confirms that the essential oil is free of contaminants and unexpected alterations during production.

The CPTG Certified Pure Therapeutic Grade quality protocol includes the following tests:

  • Organoleptic testing
  • Microbial testing
  • Gas chromatography
  • Mass spectrometry
  • Fourier Transform Infrared spectroscopy (FTIR)
  • Chirality testing
  • Isotopic analysis
  • Heavy metal testing

Historically, gas chromatography was sufficient to identify individual components in an essential oil. However, as more sophisticated methods for developing synthetic essential oil products formed, further validation methods were needed. Over time, additional testing methods such as mass spectroscopy, chiral analysis, FTIR Scan, carbon isotope analysis and others have been developed to more accurately identify each individual essential oil constituent.

Organoleptic Testing

Organoleptic testing involves the use of the human senses— sight, smell, taste, and touch. To expert distillers, the senses are used as the first line of quality testing to provide immediate clues to the acceptability of a product. Oil that has an unusual smell, uneven consistency, or strange color instantly tells the distiller that something is wrong. Often times, this testing is used as a preliminary quality control step before any other tests are conducted.

Microbial Testing

Microbial testing involves analyzing a batch of essential oils for the presence of bio-hazardous microorganisms such as fungi, bacteria, viruses, and mold. The process involves drawing a sample and then adding that sample to a sterile growth medium in an enclosed dish or plate. The sample is incubated for a period of time and then observed for microbial growth. This test is performed on product entering the manufacturing facility and on finished products prior to distribution to ensure that the product has not been contaminated during the filling process.


Gas Chromatography and Mass Spectrometry Analysis (GC/MS)

In Gas Chromatography, an essential oil is vaporized and passed through a long column to separate the oil into its individual components. Each component will travel through the column at a different speed, depending on its molecular weight and chemical properties, and is measured as it exits the column.Using this testing method, quality control analysts can determine which compounds are present in a test sample.

Mass Spectrometry is used together with Gas Chromatography to further determine the composition of an essential oil. In Mass Spectrometry, the constituents previously separated by GC are ionized and sent through a series of magnetic fields. Using molecular weight and charge, the amount of each constituent can be identified, providing additional insights into the potency of the essential oil.


Fourier Transform Infrared Spectroscopy

Fourier Transform Infrared Spectroscopy (FTIR) is conducted to ensure the potency and consistent quality of a batch of essential oil. This testing method identifies the structural components of essential oil compounds. In an FTIR scan, infrared light of different frequencies is shined through a sample of essential oil and the amount of light absorbed by the sample is measured. The quality of the sample is determined by comparing the results from an FTIR reading to a historical database with absorption patterns of high quality samples.


Chirality Testing

Chirality, a word derived from the Greek word “hand,” is a term used to describe the 3D orientation of a molecule. Just as you have two hands, chiral molecules exist in two forms, distinguished as either the right or the left hand. You may visualize this principle by looking at your hands; when placed side by side, they are mirror images of each other. However, when placed on top of each other, no matter how you turn them, you cannot get them to line up exactly. In molecules, each “hand” has different chemical properties, which affects their physiologic interactions in the body. One hand is produced predominantly in nature. However, in a laboratory environment, the ratio of right- to left-handed molecules is always 50/50 due to their structural similarities. The ratio of right- to left-handed constituents can be determined through a special type of Gas Chromatography. Although not commonly performed on a batch-to-batch basis, this testing method is used to ensure that no synthetic elements are present.

Isotopic analyisis.jpg

Isotopic Analysis

Matter is made up of tiny chemical building blocks called elements. Although dozens of elements exist, each one is distinct due to the protons it contains. Sometimes, an element can exist in more than one stable form if it has more or less neutrons. When this occurs, the elements are called isotopes. The element carbon exists in two stable isotopes, carbon-12 (6 protons and 6 neutrons) and carbon-13 (6 protons and 7 neutrons). Because essential oils are organic compounds, they are composed primarily of carbon atoms and will have a certain ratio of carbon-12 to carbon-13 isotopes. This ratio varies based on location around the world.

Using a special type of Mass Spectroscopy, it is possibleto determine which isotopes are present in an essential oil constituent and at what amounts. If sourced from the same location, every constituent in an essential oil should have the same ratio of isotopes. If a particular constituent has an isotopic profile different than that of the other constituents, then the quality control analyst will know that the oil contains an adulteration.

Heavy Metal Testing

Heavy Metal testing shows the amount of heavy metal content in the essential oil. When properly distilled, essential oils should not contain heavy metals. ICP-MS testing uses a high-energy medium called Inductively Coupled Plasma (ICP) to ionize the sample. The sample is then run through a mass spectroscope, which separates the sample into its elemental parts and provides a reading about which elements are present and at what quantities.

Reliable Sources on Essential Oil Research


Since 1950, over 120,000 scientific research articles have been published on essential oils and their chemical constituents. But only recently have scientists realized the potential applications of essential oils to healthcare. Consequently, the last two decades have witnessed an explosion in essential oil research. Three quarters of all of the studies ever published on essential oils were published after the year 2000.

Despite this explosion of scientific research, essential oils have not yet become integrated into clinical healthcare. This is partly because much of the research, while promising, is still experimental, and essential oils for now are considered alternative and complementary solutions. Also, the essential oil industry is limited in how it explains the benefits of essential oils since they are not registered as drugs.

Because of these limitations, many essential oil users and healthcare practitioners have shown increasing interest in doing personal research to help them understand the properties of essential oils. Unfortunately, there are many sources on the web containing information that is either misleading, false, or at best ill-supported by scientific findings. At doTERRA, we encourage the use of scientific research to validate the proper use of essential oils. We have put together a list of reliable sources that you can use to educate yourself on the biological activity of essential oils.

  1. Aromatic Plant Research Center (APRC)
    APRC is a state of the art laboratory that is proud to guarantee the purity of essential oils. It is a free database devoted to essential oil research and publications. APRC aspires to reimagine the essential oil industry by conducting state-of-the-art quality testing, performing groundbreaking research, producing cutting edge publications, and creating unparalleled educational materials on essential oils.
  2. PubMed
    PubMed is a free search tool that you can use to browse the MEDLINE database, an enormous compilation of research maintained by the US National Library of Medicine (NLM) and the National Institute of Health (NIH). PubMed is the library of choice for most physicians and scientists looking to find research on any topic in healthcare. Two drawbacks to using PubMed are that some research articles aren’t included in the MEDLINE database, and often searches for essential oil research can be cluttered by unrelated research studies. Many of the studies in this database are only accessible with a paid subscription to the publishing company.
  3. Google Scholar
    Google Scholar is also a free search tool, and you can use it to find any research article on the internet. Many of the studies that appear in a Google Scholar search are only accessible with a paid subscription to the publishing company. Like PubMed, one potential drawback is the cluttering your results with articles not pertinent to your search.
  4. AromaticScience
    AromaticScience is a free database devoted specifically to essential oil research publications. The library includes a search functionality, article abstracts, and links to the full text. Often the full text is only accessible with a paid subscription to the publisher. Newly published essential oil research studies are posted to AromaticScience on a daily basis.


    Essential Oils 
    Natural aromatic compounds extracted from seeds, bark, stems, roots, flowers, and other parts of plants. Essential oils contain natural and unique properties that can have powerful benefits on your health and overall wellness.

    CPTG (Certified Pure Therapeutic Grade)
    doTERRA quality protocol in which each batch of oil undergoes a multi-phase chemical composition inspection.

    Carrier Oil
    A lipid-based substance used to dilute essential oils. doTERRA Fractionated Coconut Oil is an excellent carrier oil option because of its long shelf-life and light, non-greasy texture.

    The process of extracting essential oil from plant material.

    Cold Press Distillation/Expression 
    Most commonly used method for obtaining citrus oils. This process uses a mechanical press to squeeze essential oils from plant parts.

    Steam Distillation 
    The most common distillation method. This process uses low-heat pressurized steam to circulate through plant parts and extract oils.


    Essential oils that can be used aromatically. Diffusion is one of the most popular ways to enjoy the aromatic benefits of essential oils.

    Essential oils that can be used topically, which means you can apply them directly on the skin or mix them with carrier oils or other personal care products.

    Essential oils that can be used internally. You can add oils to beverages, take them in doTERRA Veggie Caps, take doTERRA essential oils supplements, or use them in your favorite recipes.


    A category of essential oils that should be mixed with a carrier oil. The carrier oil will help “carry” the essential oils onto the skin.

    A category of essential oils that can be applied topically without dilution because of their extremely mild chemistry.

    A category of essential oils that should be diluted for young or sensitive skin.


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