image of essential oils with aloe vera plant and ceramic bowl for the post How Essential Oils Work: A Lesson in Science

How Essential Oils Work: A Lesson in Science

Please note that this article may contain affiliate links. As an Amazon Associate, I earn from qualifying purchases at no additional cost to you. You can read more at the bottom of this page or read my full disclosure on my Affiliate Disclosure Page

As dependence on prescription opioid medications, and even antibiotics, reaches an all-time and alarming high, many people who suffer from conditions like chronic pain and anxiety are seeking relief from safer, natural home remedies.  If this sounds like you, you may wonder how essential oils work.

Aromatherapy, or the use of essential oils, goes back thousands of years, when the ancient Egyptians first burned incense made from aromatic woods, herbs and spices.  We even have numerous references to essential oils in the Bible. Today, the essential oils industry has evolved into more than a $12 billion global business.

Essential oils have been studied and proven to help with a multitude of issues including difficulty sleeping, nausea, stress and anxiety, headaches, allergies, pain and gut health.

Despite the increasing popularity and widespread use of essential oils, they are not regulated by the FDA.  Additionally, not all essential oils and brands are created equally.  

image of essential oils with chemistry notes underneath with text overlay How Essential Oils Work: A Lesson in Science

This may have you wondering: How do essential oils work? How do you use them? Are there different types or forms of aromatherapy?

Just a heads up, we are going to dive pretty deep into the biology and chemistry of essential oils, but I promise that when you are done reading this post, you will no longer wonder how essential oils work.

Let’s start with some basics about essential oils.

What are Essential Oils?

Aromatherapy comes from the words “aroma”, which means fragrance or smell and “therapy” which means treatment. Aromatherapy is a natural way of healing a person’s body, mind, and soul.

Aromatherapy has been proven as an effective treatment for a number of conditions. Research shows that essential oils began gaining popularity in the late 20th century and continue to grow in usage in the 21st century, as well. 

Essential oils have increased in usage for therapeutics, cosmetics, fragrance and spirituality.

Essential oils are highly concentrated substances which are extracted from flowers, leaves, stalks, fruits and roots, and some are even distilled from resins.

Essential oils are a combination of saturated and unsaturated hydrocarbons, alcohol, aldehydes, esters, ethers, ketones, oxides, phenols and terpenes, in which each produces characteristic aromas. They are colorless, often pleasant smelling liquids with high refractive index. Essential oils are extremely potent and concentrated.

The chemical components evaporate from the plants and shield them from bacteria, diseases, funguses, pests and even protect the plant from temperature fluctuations.

Those chemical components are the reason why essential oils work.  Their chemical character is the reason that essential oils can be antibacterial, antiviral, anti-inflammatory and an immune booster with hormonal, glandular, emotional, circulatory, calming effects, memory and alertness enhancing, according to research studies.

How Essential Oils Work

To understand how essential oils work in the body, we need to look at HOW the oils are introduced to the body.  As mentioned above, there are three ways that essential oils can be used: aromatically, topically and internally. (Note: not all company’s essential oils are ingestible, only Young Living has FDA approval for dietary use).

We are going to look at how essential oils work through inhaling and topical use to understand how aromatherapy works.

Many people who suffer from conditions like chronic pain and anxiety seek relief with safer, natural home remedies.  If this is you, you may wonder how essential oils work. Click To Tweet

Two Main Routes of Absorption in Looking at How Essential Oils Work

Inhaling Essential Oils

When inhaling them, essential oils work in communication between your nose (your olfactory bulb) and your brain (the limbic system). Any time you smell something, particularly in natural fragrances like essential oils, you inhale volatile particles called “esters”. These chemicals are what gives food flavor and allows us to smell aromatic substances. The sense of smell, like taste, comes from specialized sensory cells found in a small patch of tissue inside the nose. 

In many cases essential oils will enter the body both via absorption through the skin and via inhalation; this can have a compounded positive effect.

The process of the communication between the nose and the body, goes like this:

The odor (esters) floats in the air reaching the nostrils and dissolving in the mucus (which is on the roof of each nostril). Underneath the mucus, in the olfactory epithelium, which is specialized receptor cells called olfactory receptor neurons, detect the odor. These neurons are capable of detecting thousands of different odors. 

Next, the olfactory receptor neurons transmit the information to the olfactory bulbs, which are located at the back of the nose. The olfactory bulbs have sensory receptors that are actually part of the brain which send messages directly to the most primitive brain centers where they influence emotions and memories (limbic system structures) and higher centers where they modify conscious thoughts (neo-cortex). Helping us to distinguish different scents, like grapefruit from cinnamon, for example.

Once the oils are in the system, they regulate themselves and work in a friendly manner at the site of malfunction or at the affected area. This type of therapy utilizes various permutations and combinations to get relief from numerous ailments like depression, indigestion, headache, insomnia, muscular pain, respiratory problems, skin ailments, swollen joints, urine associated complications etc.

image of the brain and a closeup look at the limbic system for the postHow Essential Oils Work: A Lesson in Science

The limbic system: the brain of emotions

The olfactory bulb is one component of our limbic system. The information captured by the sense of smell goes directly from the olfactory bulb to other structures of the limbic system. The limbic system is a network of connected structures near the middle of the brain linked within the central nervous system. These structures work together to affect a wide range of behaviors including emotions, motivation, and memory. This system deals with instinctive or automatic behaviors, and has little to do with conscious thought or will. The limbic system also deals with translating sensory data from the neo-cortex (the thinking brain) into motivational forces for behavior.

The limbic system is centrally involved in the mediation between a person’s recognition of an event, their perception of it as stressful, and the resulting physiological reaction to it, mediated via the endocrine system. Stimuli are processed conceptually in the cortex, and passed to the limbic system where they are evaluated and a motivational response is formulated. This process forges a new memory, called what-when-where memory. Our memories are multi-sensory, for instance, when you think about how a chocolate chip cookie smells, it will remind you of your grandmother. These scents produce an emotional reaction, which in turn produces a physical reaction.

There is a lot of research supporting the use of essential oils for a variety of health benefits and more being studied regularly. Whether you need an energy boost to start your day, help with falling or staying asleep or support for stress and anxiety, essential oils are a powerful, safe and natural way to improve your quality of life.

Benefits of inhalation

1.      Rapid absorption into the bloodstream.

2.      Direct effect on an infection within the respiratory system.

3.      Direct effect on congestion within the respiratory system.

4.      Direct effect on the central nervous system.

Safety considerations

1.      Not all oils can be used for inhalation. For example, oils high in phenols, aldehydes (citral in particular) and some monoterpenes can be irritating. This depends on the individual and may require some experimenting.

2.      Some oils may be contraindicated with asthma and serious allergies.

3.      Be careful with the dosage, as too much oil inhaled can cause headaches, dizziness, and can irritate the membranes of the nose and lungs.

Skin Absorption with Essential Oils

Essential oils enter our bodies either through absorption through the skin, or inhalation via the nose. They are able to affect the body through several systems and pathways and create an effect much more quickly than taking a pill, which must travel to the stomach and begin to be digested before any effect can be seen.

The skin is the body’s largest organ and anything we apply to our skin is absorbed into our bloodstream. When essential oils are applied to the skin they are absorbed and travel around the body via the bloodstream. In this way they are able to deliver a range of benefits to the body’s systems and organs. Absorption is increased by massage, as this increases the circulation in that area of the body. Heat can have a similar effect, allowing better absorption of the molecules in the oil.

Skin is referred to as “cutaneous tissue” or “dermis” or “dermal tissue” in medical terminology. You may see these terms used in other Aromatherapy literature. Since skin covers the entire body, you will most likely be applying essential oils to it. Applying essential oils to the skin affects the skin directly, and is another method of introducing the oils into the bloodstream.

Even though the skin is waterproof, it is a dynamic organ that can absorb topical substances. Lately, pharmaceutical companies have been taking advantage of the absorbing ability of the skin by creating medicated skin patches. Examples include the nicotine patch, nitroglycerin, hormone patches and more. It’s always safe to assume that anything applied to the skin can cross into the deeper tissues and into the bloodstream.

The outer layer of skin is actually made up of dead skin cells and keratin. Keratin is a tough wax-like substance. The skin has many layers, each with a special name. The outermost layer of skin is called the “stratum corneum.” The stratum corneum creates a very strong barrier. Have you noticed any leakage from your skin lately? Probably not, thanks to all the layers protecting you, especially the stratum corneum.

In the previous experiment comparing the inside of your mouth to the skin on your forearm, you learned that skin is thicker and less sensitive than mucous membranes. The difference in thickness and sensitivity means that a wider variety of oils can be used on the skin than on the mucous membranes.

The skin has different depths and sensitivities depending on where on the body it is located. For instance, the skin on the palms of your hands and soles of your feet is thicker than your forearm and ankle skin. Palms and the soles of feet have an extra layer of skin.

image of three bottles of essential oil on table with pine branch for the post How Essential Oils Work: A Lesson in Science

How do essential oils penetrate the skin?

The skin has four layers (five on the palms and the soles of feet), as well as keratin, which acts like “skin glue.” In order for something to move through this tough barrier, it must be very small. Additionally, it must be attracted to lipids (fats), since the skin has many lipid components. Consider the term, “essential oil,” which we commonly use. Although essential oils are not made of lipids, they are lipophilic meaning they are attracted to lipids and are fat-soluble.

Essential oils are made up of hundreds of individual chemical components. Their ability to penetrate the skin depends on their size, volatility, and their solubility in lipids and/or water. Generally, a smaller molecule will pass through more easily and quickly than a larger molecule – but even the large, non-volatile molecules will penetrate over a 24 hour period.

Lipid soluble components will gain access via lipid-rich cell membranes, while water-soluble components will gain access via sweat ducts.

Each layer of skin is made up of many individual cells. These cells stick together tightly, but tiny lipid-soluble (able to dissolve in oil or fat) molecules can work around these bounds. Also, hair follicles and sweat glands extend through several layers of skin, so some molecules can slide down a hair follicle. On the other side of your skin—the side facing into the rest of your body—is a network of capillaries. Once essential oil components make it through the layers of skin, they are taken up by the blood and travel throughout the body.

The ability of essential oils to penetrate the skin depends on the permeability of the skin. “Permeability” means “able to be penetrated.” The more permeable the skin, the quicker the oils cross the layers and enter the bloodstream.

Most Permeable:   

  • Genitals *
  • Head
  • Trunk
  • Limbs

Least Permeable:  

Palms and soles

* Genitals are not the best place for essential oils unless you are dealing with an infection—and then you must proceed carefully with well-diluted, skin-safe oils!

It is important to keep the dynamics of skin depth, sensitivity, and relative permeability in mind when considering the use of essential oils. This will aid you in making safe blends and applying them to specific areas for specific reasons. As a certified aromatherapist, I work with clients every day and help them make choices right for them and for their wellness.

Absorption rates of skin versus mucous membranes: Think in terms of thickness. The skin is thicker than mucous membranes, and the skin has a layer of keratin. Absorption of essential oil components into the bloodstream occurs more quickly through mucous membranes than through the skin.

Benefits of skin application

  1. It can be healing for the skin itself, while simultaneously addressing other concerns.
  2. Excellent for local inflammation or tissue healing from an injury.
  3. It can have strong analgesic (painkilling) effects.
  4. It allows for slow, continuous absorption over a period of time, especially if applied during a therapeutic massage.
  5. It can be applied directly over the area of concern.
  6. Easy to use on a daily basis, and easy to carry around with you.
  7. Essential oils are easily absorbed by the skin thanks to low molecular weight and due to being lipid-soluble.
  8. Areas with thin skin, lots of hair, and mucous membranes absorb more readily. Palms and the soles of feet absorb the least amounts of oil.

Safety considerations

  1. Irritation of the skin, particularly with oils containing phenols, aldehydes, monoterpenes.
  2. Care needs to be used when applying over areas that have been in regular contact with perfumes and synthetic cosmetics.

Types of Aromatherapy

Cosmetic aromatherapy

This therapy utilizes certain essential oils for skin, body, face and hair cosmetic products. These products are used for their various effects as cleansing, moisturizing, drying and toning. A healthy skin can be obtained by use of essential oils in facial products. On a personal level, cosmetic aromatherapy of full-body or foot bath will be a simple and an effective way to have an experience. Similarly, few drops of appropriate oil give a rejuvenating and revitalizing experience.

Massage aromatherapy

The use of grapeseed, almond, or jojoba oil, pure vegetable oil or other carrier or massage oils during massage has been shown to have wonderful effects. This is also known as the healing touch of massage therapy.

Medical aromatherapy

The founder of modern aromatherapy Rene-Maurice Gattefosse has used essential oils to massage patients during surgery, thus utilizing the medical aromatherapy knowledge of the effect of essential oils on promoting and treating clinically diagnosed medical ailments.

Olfactory aromatherapy

Inhalation of essential oils has given rise to olfactory aromatherapy, where simple inhalation has resulted in enhanced emotional wellness, calmness, relaxation or rejuvenation of the human body. The release of stress is welded with pleasurable scents which unlock odor memories. Essential oils are complemented to medical treatment and can never be taken as a replacement for it.


In psycho-aromatherapy, certain states of moods and emotions can be obtained by these oils giving the pleasure of relaxation, invigoration or a pleasant memory. The inhalation of the oils in this therapy is direct through the infusion in the room of a patient. Psycho-aromatherapy and aromacology, both deal with the study and effects of aroma be it natural or synthetic. Psycho-aromatherapy has limited itself with study of natural essential oils.


From Greek roots: animal-medicine-knowledge. Based on the fact that animals have an innate ability to know what they need for health.  Allowing animals to choose which oils are best for them.  Using oils on animals.

What to Look for When Buying Essential Oils

When shopping for essential oils, note that not all brands are created equal. Many mass-marked oils (i.e. sold in grocery stores or big-box retailers) include a combination of lesser and/or synthetic oils. The FDA does not regulate essential oils.  A brand only needs to include 5% of pure oils to label the bottle 100% pure, when, in fact, you may be getting only a fraction of oil, possibly a 2nd or 3rd batch and the rest synthetics, chemicals or fillers.

It’s important to research the botanical name, the corresponding GC/MS (purity) report before purchasing a specific brand of essential oil. Young Living has a seed to seal program which ensures the highest quality of oil, 100% pure, in all of their products, which is why I choose to buy my oils from them.

You may enjoy this brief video on how essential oils work via skin absorption:

If you have any questions about how essential oils work or which oils may be right from you, email me at [email protected] or comment below. I’d love to help!

Sharing is Caring!