All About Essential Oils


History, Misconceptions, and Proper Use

With the current rise in natural/green/clean/holistic/organic (pick your favorite adjective 👈) beauty, there is a lively discussion happening in these circles around the use and safety of essential oils in skin care products. Before making up your mind on essential oils, it’s important to understand some of the basics - and some of the intricacies - of these volatile (that evaporate quickly) aromatic fluids and why having all the information at hand before making a decision is, ahem, essential. 😉

‘God of his infinite goodnesse and bounty hath by the medium of plants, bestowed almost all food, clothing and medicine upon man.’

Gerarde’s Herbal (1636)

Plants have been a part of human medicine since probably the beginning of civilization. The early hunter/gatherers must have noticed how the leaves of certain plants made food taste better, aided digestion, created pleasant smoke, or alleviated pain. During the Neolithic period (about 6,000 to 9,000 years ago), man discovered that certain crops like olive, sesame, and flax contained fatty oils, so it is safe to assume that if people were using herbs and plants in baking, cooking, and medicine, then they probably had already been making scented oils through infusion methods.

Although the history is spotty, it’s presumed that the first of the major historic civilizations to use an alembic still (the device used to make essential oils, as well as various alcohols, through distillation) was the ancient Egyptians at around 2,000 BC, although this is far from confirmed. They certainly had a strong affinity towards essences and perfumery, often times entombing their rulers with pots of scented oils inside the pyramids, and believing that the efficacy of aromatic oils was attributed to them being originally formulated by the gods.

The Romans, however, were more lavish in the way in which they used perfume than the Egyptians. They would encase their perfumery in bottles or containers made of onyx, alabaster (marble), glass, and even ivory. It is also assumed that some of the less famous civilizations from the Middle East, Turkey, India, China, etc. also used the aromatic powers of plants in either therapeutic or cosmetic ways.

The history of human medicine began with plants, and they continue to be used so today. Most people have at least a peripheral knowledge of the fact that plants were, or are, considered as medicinal. But too few have taken the time to understand why they are medicinal. This is likely due to the recent rise of “Western Medicine” over the last century and its preference of the concentrated synthetic isolates of plants in the forms of pills rather than whole-plant remedies.

This is relevant when pertaining to essential oils because knowledge of essential oils and whole plants is suspected to be limited as they are not part of the typical curriculum in most medical schools. This is unfortunate as it means that there are fewer studies and data around essential oil composition and effects than, say, pharmacological ones which leaves the door open for, perhaps, less-scientific speculation.

That being said, there are some that have taken the torch to lead the way in understanding essential oils, the godfather of which today is widely considered to be Robert Tisserand. Although he has many books published on the subject, his Essential Oil Safety textbook from 2014 is extensively viewed as the go-to on essential oils for many cosmetic formulators, aromatherapists, and “alternative” healers. In this massive undertaking, Tisserand profiles a huge variety of essential oils, merging data from numerous studies in order to give all the necessary information pertaining to essential oils for inhalation, ingestion, or topical application.

But what exactly are essential oils? Not technically “oils”, more highly concentrated extracts, essential oils represent the essence or spirit of a plant, evaporating into the air if not contained. They are volatile, aromatic fluids held in specialized glands or cells within the plant’s tissue. They are used by plants both for pollination and protection: they attract beneficial pollinators as well as protect themselves from different animals and insects, even disease. There is also a theory that they evolved over time to be attractive to humans to help with their propagation!

In most plants, the essential oils are present in tiny droplets in almost every part of the plant: flowers, roots, leaves, seeds, barks, woods, resins, grasses, and on the rinds of fruits. While they are in, or on, the plant, these essences are constantly changing their chemical compositions. They actually move to different areas of the plant depending on the seasons, even the time of day. This is why the best, highest-quality essential oils can be rather expensive since the quality of the oil depends on the time of day the plant material was picked, the time of the year, the weather conditions at the time of picking, the expression of the earth or condition of the soil, wind, water, rain, altitude, latitude, light and shade (the terroir), and even the method of cultivation.

This helps explain why some essential oils from a particular region are treasured above others, where the weather conditions are at the most ideal and the people working with the plants understand the best way to make them (which is why at Maison/Made we rely on Biodynamic purveyors of EO’s who consider all these factors when producing them). Bulgarian rose is a great example of this, as you will notice that EO’s of Bulgarian rose typically commands a much higher price point. This also makes it easy to see why adulteration (the dilution of an essential oil with cheaper oils or isolated constituents to maximize profits) is unfortunately quite common in the higher-priced essences, and all the more reason to buy your EO’s from a reputable and trusted source.

Because of their fragile nature, the storage and degradation of the oil is incredibly important as well. Unfavorable conditions are categorized into 3 main factors: heat, oxygen, and light. Like any organic matter, EO’s degrade over time, so if packaged or stored incorrectly, EO’s will degrade fast, lose their aromatic quality and therapeutic value, something you definitely don’t want in your skincare product or diffuser. This means that EO’s should be stored quickly after processing, or purchasing, in a dark, cool location and should be closed properly to not be exposed to air. You also want to avoid any plastic as they often contain phtalates (and other compounds) which the essential oils can extract from the plastic, meaning that glass bottles are the ideal.

Specific degradation depends on the plant, but for most EO’s a good rule of thumb is 12 months after purchase or first opening, particularly for citrus EO’s. Most other EO’s are typically good for 2-3 years, and absolutes and concretes can last even longer at up to 5 years. Also, if your bottle is 90% empty for 3 months or more, it is recommended to dispose of as well. Be careful though, they can be flammable, so make sure to dispose of them appropriately. Some EO’s, however, can actually age well like sandalwood, patchouli, and vetiver, so much so that there is market for vintage EO’s like these.

To get the oils from the plant material, there are 4 main methods of extraction: distillation, expression, solvent extraction, and CO2 extraction. The vast majority of EO’s are made through steam distillation, where, using an alembic still, steam passes through the fresh plant material and the volatile plant components are vaporized and then cooled, producing a mixture of water and “oil,” hydrosols and essential oils, respectively.

The expression method of extraction is primarily used for citrus oils where, say, lemon peels are pressed to extract the oil in the rinds. This is probably the least common method as it only applies to a small amount of essential oils.

Solvent extraction is a process by which the plant material is “washed” in a solvent, like ethanol, until the oil is dissolved in the solvent, which is then separated by being distilled at a precise temperature, thereby condensing the EO but not the solvent, although trace amounts can still remain. The oils produced with this method of extraction are not technically essential oils, they are called absolutes or concretes which have a higher concentration of other constituents making the aroma typically stronger than in steam distilled EO’s. This makes them quite common in perfumery, and less common in skincare products.

CO2 extraction is the 4th method of extraction whereby pressurized carbon dioxide “pulls” the phytochemicals from the plant material, supposedly without any residue, which can be the case with solvent extraction. This is the more recent method and therefore much research has not yet been done.

Essential oils are made of an estimated 50,000 to 100,000 different compounds (chemical constituents that make up essential oils, giving them their aroma, therapeutic action and potential contraindications), where a single EO can contain anywhere from 5 to approximately 400, so it is easy to see why this subject can be quite complex. That being said, they are generally comprised of alcohols, phenols, esters, ketones, aldehydes, and terpenes. Without diving too deep into the science, monoterpenoids and sesquiterpenoids hydrocarbons (made of hydrogen and carbon) typically make the bulk of an EO composition, and they are also the starting building blocks for the other aforementioned components.

The sourcing of essential oils is also a consideration as there are some EO’s that come from wild plants or precious woods. Rosewood, spikenard, and agarwood (aka “oud”) are all trees that are in danger from exploitation as the trees are cut down (and oftentimes not replaced) to make the essential oils. At Maison/Made, I do not formulate with any essential oils that threaten the survival of these plants, or the animals and insects that rely on their existence. In regards to regulation, IFRA (the International Fragrance Association) regulates the safety of fragrances used in cosmetics products worldwide, and in the EU the European Commission has a database of ingredients by their INCI name, called CosIng, where it provides information on ingredients, and official regulation guidelines in what’s called the Cosmetic Regulation No 1223/2009. In Europe it’s required to list the allergens that some EO’s contain, whereas in the US it isn’t and they are often lumped together under the term “Fragrance” or “Flavor”... Two of the most common allergens you’ve probably seen are limonene and linalool, both terpenoids, and both with low toxicity.

Quick note here, namely that there is no such thing as “no toxicity” or “non-toxic” essential oils because everything can be toxic: toxicity is a matter of dosage, and even simple, seemingly innocuous things like water and oxygen can be toxic at high doses.

However with EO’s there is an important concept related to this, phototoxicity. Phototoxicity happens when chemical constituents bind themselves to the DNA of the skin and then react to UV rays (in sunlight or tanning beds, for example), thereby damaging the tissue and killing the cells. In the applied area this results in what most resembles a sunburn: red, sensitive skin. The EO’s that pose this potential issue (which you will NOT see in our formulations) are primarily expression extracted citrus EO’s like lime, lemon, bitter orange, and grapefruit, as well as steam distilled EO’s of bergamot, fig leaf, lemon verbena, and cumin.

As for the benefits to the skin, when formulating I look at the full profile of each essential oil I am considering, not just for their individual composition, but also for how they interact with each other. Some EO properties become enhanced when mixed together, providing, for example, better skin penetration or increased antioxidant powers. Because EO’s are concentrated, oftentimes fragile materials, formulators need to know as much as we can about the cultivation, production, and storage of the oils to be sure that the ones we use in our products are not only of high quality that can perform the positive actions on the skin that we’re looking for, but that also are in the correct proportions in terms of the dermal limits of the skin, so as to not pose any potential problems for our customers.

One of the most talked about examples, at least lately, is that of methyleugenol, an ether found in a variety of EO’s, but the reason that it comes up a lot in skincare is because it is found in the EO of damascus rose and tea tree. A mild skin irritant, methyleugenol can be genotoxic and carcinogenic. But remember, it all depends on the dosage, and the European Commission mandatory directive is a limit of 0.0002%. Therefore, as long as the formulation adheres to this directive, it has been tested to not pose any adverse reactions. We don’t use it in our Extrait de Maison serum, so no need to worry about it for our product, but something to keep in mind when looking at other skincare products on the market, particularly in the US.

Two big reasons why EO’s are included in skincare products is because they can deliver some potent antioxidant properties that are not present in carrier vegetable oils (remember, they are the essences of live plants with many constituents not present in the pressed seed oils) and, because of their nature, also help in the penetration of beneficial molecules that other substances can’t match. Many of the monoterpenes and sesquiterpenes I mentioned before provide antiseptic, anti-inflammatory, antibacterial, decongestant, and/or circulation-stimulating effects, and since they usually make up the largest percentage of a given EO, they can certainly provide an added boost to a product if formulated correctly. These terpenoid compounds have also been studied for their penetration enhancing effects, where they partition into the stratum corneum (the outermost layer of the skin) and interact with tissue components to reduce the barrier properties of the skin, without damaging the underlying cells.

The bottom line is that if you are looking for natural skincare products and you see essential oils in the ingredient list, don’t be afraid! They can do a lot of good things for the skin, and are not always there simply for the fragrance. I hope that at least now you have a better understanding of why they are included in a well-balanced formula, and if you have any questions as to particular EO’s, please feel free to leave a comment below and I will get back to you!




- Tisserand, R. & Young, R. (2014) - Essential Oil Safety. Second Edition. Churchill Livingstone Elsevier.

- Bensouilah, J. & Buck, P. (2006) - Aromadermatology: Aromatherapy in the treatment and care of common skin conditions. Abingdon, OX. Radcliffe Publishing Ltd.

- Schnaubelt, K. (2011) - The Healing Intelligence of Essential Oils. The Science of Advanced Aromatherapy. Rochester, VA. Healing Arts Press.

- Rose, J. (1999) - 375 Essential Oils and Hydrosols. Berkeley, CA. North Atlantic Books.

- Wildwood, C. (1993) - Creative Aromatherapy. San Francisco, CA. Harper Collins.

- PubMed Health: Development of essential oils as skin permeation enhancers: penetration enhancement effect and mechanism of action. [accessed 2019 August 28]

- PubMed Health: Essential oils and their constituents as skin penetration enhancer for transdermal drug delivery: a review. [accessed 2019 August 31]

- National University of Food Technologies: Chemical composition of essential oil from Rosa Damascena mill. [accessed 2019 September 5]

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-The Herbal Academy: The Truth About Phototoxic Essential Oils & How To Use Them Safely. [accessed 2019 September 5]