Many people have heard of essential oils either as a recipe ingredient or as a herbal preparation. Essential oils are easy to get a hold of and easy to use. They have a variety of applications from self-care to uses in the home to uses in cooking and baking. Recently there has been a rise in popularity of these oils. This popularity focuses in part on the therapeutic uses. When we start to dig into what EO are made of and how they work on the body, it becomes an interesting mix of chemistry, body function and unanswered questions.
What Are Essential Oils?
Essential oils (EO) come from plants and are responsible for their aroma. When you smell a rose or peppermint leaves, you are detecting the EO. A plant uses these oils to help with its survival. For example, they can use them to attract bees and other pollinators or as protection against pests. The chemical composition of a plant’s EO can vary over the course of the plant’s life as it responds to the environment around it. Plants of the same species that are grown in different areas can also vary from each other in the composition of the EO.
How Commercial EO are Made
The first thing to know is that it can take a lot of plant material to make commercial EO. Rose is an extreme example where it can take 30 – 50 flowers to make one drop of EO. That’s why it’s so expensive. There are a few different ways to get the EO out of the plant.
Distillation – The plant material is exposed to steam causing the oils to release from the material. As the steam rises, it enters narrow tubing that causes condensation. The liquid that drips from the tubing (a combination of water and EO) is collected. The water and EO separate so that the oil can be taken off. This video gives you the general idea. Some other types of distillation are turbo, vacuum and hydro-diffusion.
Cold expression – The plant material is manipulated (e.g. punctured, shredded) and/or pressed in order to release the oils. A centrifuge may also be used.
Solvent extraction – Used for more delicate plants that don’t handle heat well. The plant material is soaked in the solvent (i.e. ethanol, hexane, methanol, petroleum ether, toluene) and agitated. The solvent is removed and a further process removes any wax. The end result is called an absolute. There is typically a low concentration (5-10 parts per million) of the solvent left in the absolute.
Carbon dioxide (CO2) extraction – This is a newer form of extraction. CO2 is put under high pressure where it turns into a liquid. This liquid works through the plant material extracting the EO. With the release of pressure, the CO2 returns to a gas and is removed.
The resulting EO from any of these processes are highly concentrated. This is an important point to remember when using them for any purpose. Because of the process used, only the “lighter” molecules of the plants are in the final product. EO and whole herbs will not have the same compounds (secondary metabolites). EO are part of the herb while whole herbs have all of the compounds of the herb. For this reason, when looking for the therapeutic effects of an herbal EO, you may not be able to rely on the description of therapeutic effects of a whole herb.
Another important point to remember is that EO and herb-infused oils are not the same thing. EO are the oils straight from the plant. Herb-infused oils are made by soaking herbs in a nut or vegetable oil (e.g. almond oil, olive oil). In this case oil is used as a solvent and as the base of the final product. It has a limited ability in what it extracts from the plant when compared to the processes used for making commercially EO. There are also products, such as massage oil, that may have EO added to them. If you want EO, make sure that it says 100% EO on the label.
How EO Work on the Body
This is where the “unanswered questions” comes in from the beginning of this post. The two common ways that EO are used for therapeutic purposes are by breathing them in and by applying them to the skin. Taking EO internally for therapeutic effects is very controversial. Because the oils are highly concentrated, ingesting a small amount can reach a toxic level in the body.
Aromatherapy, as defined by the National Association of Holistic Aromatherapy, is:
“…the art and science of utilizing naturally extracted aromatic essences from plants to balance, harmonize and promote the health of body, mind and spirit.”
For this purpose, EO are somehow diffused into the air. It can be with a diffuser, through a massage or even by breathing in the aroma from an open bottle. To understand how the aroma of EO work on the body, it’s best to get an idea of how we are able to smell. Odor molecules are breathed into the nose and make their way to the olfactory epithelium. These molecules become stuck there and bind to receptor cells as the molecules dissolve. The receptor cells are activated and send messages directly to the brain. Depending on the odor, different messages are sent. Once the message reaches the brain, different glands (thalamus, pituitary), the limbic system and the central nervous system become involved. Or at least that’s one theory. Research is ongoing in this area.
For topical application, let’s start with understanding what makes up the skin. The skin has three layers: the epidermis, the dermis and the hypodermis. The epidermis is responsible for keeping foreign materials from entering the body. The dermis contains the hair follicles, sebaceous glands, sweat glands, nerves, veins and arteries. The idea is that the EO molecules can bypass the epidermis by being absorbed through the hair follicles and glands and then find their way into the bloodstream and lymphatic system. From there they can travel throughout the body until they are filtered out by the liver and kidneys. EO are also used for their antibacterial, anti-fungal, anti-inflammatory, and antiseptic properties in dealing with issues on the skin. Research is ongoing in this area too.
How EO are Used
When using essential oils, it is important to dilute them before applying them to the body. Typically this is done with what is called a carrier oil. A carrier oil is usually a nut or vegetable oil. The type of oil used can depend on how slippery it is, how quickly it is absorbed into the body, what the shelf life is, its smell, etc. Sometimes the term “neat” is used when giving directions on how to apply the oil. “Neat” means to apply it directly to the skin with no carrier oil. There are very, very few EO where this should be recommended. EO are very concentrated and can be irritating to the skin; some more than others depending on the herb used.
It’s a good idea to do a skin patch test when using an oil for the first time. Better to have a small irritated patch on the inside of your arm than a flaming red rash all over your face or legs. If you are allergic to specific plants, you may also be allergic to their oils. Proceed cautiously when trying EO.
There is a standard formula for mixing EO with a carrier oil. This can also be done with lotion or cream.
- 1% – five to six drops of oil to 1 oz. of carrier oil. This is considered a mild mixture
- 2% – ten to twelve drops of oil to 1 oz. of carrier oil. This is considered a standard mixture.
- 3% – fifteen to eighteen drops of oil to 1 oz. of carrier oil. This is used short term for special instances such as acute injuries or specific illnesses.
Different EO can be used when making a single mixture and is a very typical practice. When creating your own, be sure to keep track of how many drops you’ve added and of which oil. Also make a note of when you mixed it. Put this information on a label on the container to make it easier to remember. It’s a good idea to mark when you purchased any EO and carrier oils too. This is a good place to mention the “more is not better” rule. Using more than is recommended can lead to adverse effects. If you feel dizzy, develop a headache or otherwise don’t feel well after interacting with EO, your body is trying to tell you something. Pay attention.
EO are like other herbal preparations. Light, heat and oxygen can cause their active compounds to deteriorate. They and any preparations made with them should be stored in a colored glass container in a dark location to help block out light. Always make sure the cap of the container is closed completely when not in use and store it in a cool place. EO can last anywhere from one to four years. Herbal preparations made with EO can last anywhere from a couple of months to a year depending on the preparation.
There are plenty of recipes on the internet for using EO to make home cleaning products and for using them in cooking and baking. Remember that the oils are highly concentrated so the amounts used will be small. Again, more is not better – stick to recipes from reliable sources.
So What’s A Consumer to Do?
Did I mention that these oils are very concentrated and that more is not better when using them? The great thing about EO is that they’re versatile and easy to use. That means they’re easy to abuse, too. Make sure you dilute the oils appropriately before using them on your body, pay attention to directions when using them in diffusers, and follow any recipes you use. If you feel you have had an adverse reaction, stop using them. If the symptoms don’t resolve, see your health care practitioner.
If you’ve shopped for EO, you may have noticed that some oils, like rose and jasmine, are pricey. This can be because:
- it takes a very large amount of plant material to make the oil,
- the plant material is hard to find (i.e. endangered, bad crop year, not widely grown),
- there is a large demand,
- or a mixture of these.
When looking up prices, pay attention to whether the price is for ½ oz or a full oz. so you are comparing like amounts. Look around to different suppliers to get a feel for what the current going rate is for a specific oil. If you see an oil offered for an atypical low price, be suspicious and read the label carefully. If an oil you want is out of your price range, there may be another oil that has similar properties that is less expensive.
If you’re just starting out, buy small quantities of EO and carrier oils. Pay attention to how much you’re using how often and adjust future purchases accordingly. There’s no point in getting a big bottle of carrier oil and risk having it go rancid because you don’t use it enough. You may also find that you don’t really like a certain EO/carrier oil or you have a negative reaction.
Next article – Essential Oils, Part II: Regulations
Links to Learn More
What are Essential Oils – Lots of detail – National Association for Holistic Aromatherapy
How Are Essential Oils Extracted? – Lots of detail – National Association for Holistic Aromatherapy
Aromatherapy – University of Maryland Medical Center