Monoterpenes and Sesquiterpenes in essential oil chemistry.
Super Simple Essential Oil Chemistry for Beginners.

The Chemistry of Essential Oils Made Simple -Part 1 of 3

Aromatherapy science chemistry.


Essential Oil Chemistry for Beginners.

Essential Oil Chemistry 101 for beginners.

Before reading this, I am going to link to a sister post called, “Why Essential Oils Work When Applied Topically.” It goes into how essential oils absorb into your body and why they work.

Understanding that each essential oil has its very own specific chemical make-up is crucial to understanding why that oil offers so many diverse health benefits. When we understand these things, we can know better how they work with our own personal chemical make-up. If you are new to essential oils, you have to get this.

One important thing to remember is that the chemistry information in this post and the remainder of the essential oil chemistry post is based on clinical studies, scientific studies and experimental research. Not all of these studies have been conducted on humans. There is a lot of potential for cures and treatments as found in these highly documents studies. Hopefully someday, we can find cure for cancer and other diseases based on this research.

Please note that the components of essential oils can be recreated in a laboratory but even scientists are aware that they are not nearly as effective as when they are in their whole, complete, and natural state. These studies are also done often while isolating one single component. Essential oils have hundreds or thousands of these chemical compounds in one oil. God knew what he was doing when he put them all together. Therefore, most constituents work as a team as are far more effective when working together in their natural state…in essential oils. To learn more about essential oils for natural remedies, click here.

Although there are cautions based on some components in this studies, the claims often come from overdose of or consumption of essential oils. The only deaths that have ever been reported from essential oils come from internal consumption in large quantities, usually in children. Children should never consume essential oils. Adults should not consume essential oils regularly or in more than small doses. For more information on this check out, “Is It Safe to Use Essential Oils Internally? What Do The Experts Say?” Therefore keep these cautions in mind as you use your essential oils. Click here to learn more and to help you understand safe use of essential oils.

The quality, purity and way the plants are grown is of the utmost importance when using essential oils for medicinal and therapeutic benefits.  These factors decide how potent the oils are and if they really work or not. That is why there is only one company I will ever trust with my families health. They make sure every aspect of their oils are the best quality available…in the entire world.

What is the science behind how essential oils work?
Why do essential oils work?

These statements are not regulated by the FDA and are not intended to diagnose, treat, prevent or cure any disease or illness. These statements are no substitute for professional consultation with your personal physician. Consult your doctor before making any changes and/or additions to your health care routine.

Intro Into Essential Oil Chemistry

Beginning essential oil chemistry.
Easy Essential oil Chemistry for beginners.

What Are Essential Oils?

Essential oils are volatile organic compounds. 

Volatile means they evaporate easily at normal temperatures. That is why you can open the bottle of an oil and smell it right away. 

Simply said, organic compounds are any chemical compound that contains at least 1 carbon atom. The carbon atoms are the base in which the makeup of each essential oil is built. The carbon atoms link with hydrogen or oxygen in any number of different ways. Whichever element that the carbon atom joins with determines what health benefits that oil offers.

Keep in mind that a single essential oil can contain hundreds or thousands of different chemical compounds. That is why one oil can offer so many health benefits to us. Lavender can help you sleep, help you focus and ease the pain of a burn all at the same time. Isn’t that amazing? This effect is only amplified when you blend essential oils together.

Health benefits of sesquiterpenes in essential oils.
Health benefits of essential oils. Health benefits of monoterpenes.

Categories Of Essential Oil Chemistry

Essential Oils fall in to 2 categories of chemical constituents. 

1. Terpene Hydrocarbons

2. Oxygenated Compounds

They can be divided further in to

  • Phenols
  • Alcohols
  • Aldehydes
  • Keytones
  • Esters
  • Lactones
  • Coumarins
  • Ethers
  • Oxides
 In part 1 (This Part) we will analyze Terpene Hydrocarbons.
Health benefits of oxygenated compounds in essential oils.
Health benefits of hydrocarbon sesquiterpenes in essential oils.

Terpene Hydrocarbons in Essential Oils

Research on the chemistry of essential oils.
Scientific studies on the chemistry of essential oils in aromatherapy.

Terpene Hydrocarbons have 2 categories found in essential oils.

1. Monoterpene Hydrocarbons (Monoterpenes for short)

           Monoterpene molecules are small and light so they evaporate quickly. They absorb into the skin quickly. They’re very fragrant and called top notes in perfumery. Mentally they are uplifting and energizing. Their benefits are strong because of it’s ability to cross the blood brain barrier.

2. Sesquiterpene Hydrocarbons (Sesquiterpenes for short)

         Sesquiterpenes molecules are large and heavy so they evaporate slowly. They absorb into the skin more slowly. The scents are stronger, earthier and are middle or base notes in perfumery. Mentally they are relaxing and grounding. Their benefits are also strong because of their ability to cross the blood brain barrier.

Monoterpenes and Sesquiterpenes in essential oil chemistry.
Super Simple Essential Oil Chemistry for Beginners.

The Blood Brain Barrier and Essential Oils.

Sesquiterpens  and Monoterpenes cross the blood-brain barrier and reach the brain tissue. THIS IS A HUGE DEAL WHEN UNDERSTANDING THE EFFECTIVENESS OF ESSENTIAL OILS!!!!!!

Our brain and spinal cord have a barrier of blood vessels that can be compared to a gate. It’s called the blood brain barrier. Our brain and spinal cord is the only body organ that has this. Our brain decides when to open that gate and what to let in. Brain tissue is very sensitive and susceptible to damage making it crucial to have this security system in place. No other body organ can manually “filter” what goes in to it BUT our brain and spinal cord. The purpose of the blood brain barrier is to prevent harmful substances from entering our brain and spinal cord and welcome helpful substances in.

Essential oils containing monoterpenes or sesquiterpenes are allowed to come in this gate…

THIS IS EXTRAORDINARY! This literally means that the therapeutic benefits can go through our blood stream directly to our brain tissue and solve the problem at the source! A lot of medications prescribed by physicians cannot even cross the blood brain barrier because the it’s filtration system is still a bit of a mystery to us.

The AMA (American Medical Association) stated that if they could find a substance that would cross the blood brain barrier the would be able to find a cure for diseases like Alzheimer’s Disease, Multiple Sclerosis, Lou Gherkins, Parkinson’s Disease and so much more. Yes, the AMA said this!


This is why applying essential oils topically is so helpful. In my sister post I mention that essential oils can penetrate our cells. They do not only REACH our cells…they penetrate INTO our cells. This is as extraordinary as well because our cell membrane acts as a gate too. They’re both like the secret service agents of our body.

Yes, they heal our cells from the inside and directly from our brain. WOW, this is unbelievable!!!

YES THERE IS MORE! I have a great post about the science behind aromatherapy and it reveals this; Essential oils travel directly to the limbic system in our brain when we smell them. Anything else must stop at the “central control” part of our brain FIRST before it moves on to its destination. No, not when we smell essential oils…it goes directly to the limbic system. The limbic system is responsible for emotions, instincts, behaviors, libido, and memories PLUS a lot more.

1. Monoterpenes In Essential Oils

Monoterpenes are in nearly every essential oil there is! This subcategory of Terpene Hydrocarbons has around 2,000 different variations. I will not get into all of those of course, I will just say that all the different monoterpenes are similar in their benefits although the chemical makeup does vary greatly.

Health benefits of Monoterpenes:







-Analgesic (Pain Relieving)

-Detoxifying to the liver, gallbladder and kidneys

-Cancer Preventative or Supplemental Cancer Treatment

Essential oils high in monoterpenes are very sensitive to heat and air which means they can “go bad” if exposed to sunlight, fluctuations in heat or oxygen. 

This is why essential oils come in dark amber glass bottles. The amber glass bottles protect from the sun’s UV rays and helps keep control heat. Essential oils must not get overheated. If the temperature where essential oils are stored cannot be effectively controlled, it is highly recommended that you store them in the refrigerator.

The plug in the opening of the glass bottle is called an orifice reducer and it helps reduce oxygen from getting to the oils and prevent oxygen from getting trapped inside the bottle.

It is VERY important to store your oils properly for these reasons. Citrus oils especially, are very high in monoterpenes and must be stored properly and used within 1-2 years of opening (if opened regularly because of oxygen exposure) in order to avoid oxidization. Using an oxidized oil make cause skin reactions and possible burns. There is no shelf life on essential oils UNLESS they are not taken care of. They do not go rancid, they just oxidize.


Common Monoterpenes In Essential Oils

Limonene (Lime-o-neen)

Limonene is by far the most common monoterpene in essential oils. Scientific studies have shown the different health benefits for limonene are:




Limonene prevents cancerous cells from multiplying and repairs damage done by chemotherapy treatments. Over 200 studies have been done of the effects of limonene as an anti-cancer treatment; the results have been astonishing, showing that limonene specifically targets and destroys cancer cells ONLY. It has proven to prevent and treat breast cancer with magnificent intensity. It does not kill any other cells-just cancer. Wow. It also shrinks tumorous cells by inhibiting G proteins. Most chemotherapy treatments kill cells-limonene targets cancer cells and leaves healthy cells alone. It actually increases the effectiveness of certain cancer treatements as well.


Limonene reacts very strongly to serotonin in our body and eases depression, anxiety, stress and other mental disorders. It is very powerful in this area.

Immune Support

Limonene has immune boosting properties by naturally helping our body create more antibodies. 

Analgesic (Pain Relieving)
One study showed 63 out of 123 women in labor found pain relief in using limonene alone. 

Weight and Digestive Support
It can suppress your appetite, increase metabolism, aide absorption of healthy fats, reduces bad cholesterol and increases good cholesterol. It helps with bowel regularity and indigestion as it absorbs easily into the intestinal system. It lowers blood sugar and gets rid of insulin resistance. 

Limonene detoxifies your liver and kidneys by removing fat build up and waste. It relieves heartburn and GERD (reflux) by neutralizing gastric acids. One study showed that in 97% of people, gallstones were completed dissolved by using limonene.

It is used commercially in bug repellents, insecticides and even prescription flea medications. Limonene effects are so broad and also widelhy documented through science it is difficult to cover them all. The recommended daily dose of limonene is 3000mg.


Antioxidants fight free radicals in our body that cause oxidative stress. Free radicals damage DNA which causes cell damage like premature aging and even can lead to cancer. 


Limonene reduces swelling, pain and discomfort due to inflammation. This includes diseases arthritis, rheumatism and IBS (Irritable Bowel Syndrom).


It has shown to treat bronchitis.


Essential Oils High In Limonene

  • -Citrus Fresh
  • -Grapefruit
  • -Orange
  • -Carrot
  • -Lemon
  • -Lime
  • -Fennel
  • -Bergamot
  • -Tangerine
  • -Neroli (Blossom of the Bitter Orange Tree)
  • -Spearmint
  • -Pine

Pinene In Essential Oils

Pinene has two different types, A-Pinene AKA Alpha-Pinene or B-Pinene AKA Beta Pinene. 

They are found together far more often then not as they work hand and hand. 

The Pinene family works quite well on it’s own but works best when paired with other chemical compounds that complement it’s own abilities. 

Alpha-Pinene is found in pine as the name suggests and is responsible for the pine smell.

Beta-Pinene has a slightly more herbaceous and earthy scent like that of dill or fennel.

Alpha-Pinene (Al-fa Pie-neen)

Another popular monoterpene is Alpha-pinene.  Alpha-pinene alone has a wide range of health benefits but is even more effective when paired with complementary constituents in addition to enhancing their benefits.


It stops tumor and cancer cell growth which makes it an effective supplement to other cancer treatments.



It is effective on a wide variety of bacteria and virus. It can even help fend off parasites and infections.


Highly antibiotic especially against Staph infections and MRSA.




Alpha-Pinene is a bronchodilator which means it opens airways (the bronchi) allowing more oxygen to enter our lungs and cells. Therefore, it a great treatment for asthma and other respiratory diseases. It can be used for colds, the flu and congestion. It has treated some difficult strains of bronchitis.  



It is high in antioxidants, which help our bodies fight off free radicals and oxidative stress whether it is from lifestyle or from certain medications like aspirin. 


It helps fight fatigue and gives you energy.



It counteracts mental disorders that cause memory dysfunction such as Alzheimer’s Disease and other forms of dementia by containing memory boosting substances. 

Tissue Support

Alpha-pinene is anti-catabolic, meaning it prevents breakdown of components of the body like muscles, organs and other tissues. This makes is especially helpful to add to your workout routine to grow muscle and prevent muscle breakdown.  Use it as a supplemental health routine to decrease the effects of diseases like AIDS that break the body down.


When used topically it can helps balance oily skin and heal blemishes like acne and eczema. It is known to nourish and rejuvenate skin which can also help reduce wrinkles and signs of aging.

Oral Health

It can help keep your mouth clean and healthy.


It can be used to help reduce pest attacks.


Beta-Pinene (Bay-ta Pie-neen)


B-Pinene is very similar theraputically to A-Pinene and found together more often than not.





B-Pinene is one of the most effect constituents for overall mental health. It stimulates the serotonin, dopamine, norepinephrine, epinephrine, and histamine neurotransmitter systems in the brain. Since it targets all of those receptors it works much better and lasts longer than other treatments for disorders such as nervousness, depression, anxiety, stress and more.j


It is antibacterial but not as much as A-Pinene. It slows the growth of many pathogens and reduces the damage they cause.


B-Pinene shows to kill cancer cells and slow the rate or reproduction.

Essential Oils High In Pinene

  • -Pine
  • -Rosemary
  • -Frankincense
  • -Juniper
  • -Fennel
  • -Cypress
  • -Sage
  • -Wild Orange
  • -Helichrysum
  • -Eucalyptus
  • -Oregano
  • -Camphor
  • -Spruce
  • -Goldenrod
  • -Nutmeg
  • -Black Pepper
  • -Niaoli
  • -Coriander
  • -Roman Chamomile

1,8 Cineole (Sin-e-ol)

There is another popular monoterpene called 1,8-Cineole. 

1,8-Cineole has a few different names such as Eucalyptol or just Cineole for short. Eucalyptol is the primary chemical constituent in Eucalyptus, giving it the name eucalyptol. In this article I will just call it cineole.







Cineole is an airborne antimicrobial. It is a strong cough suppressants in part because its antispasmodic by nature. It alleviates symptoms of cold/flu medicines, allergy and congestion remedies. Cineole’s response for effectively eliminating or treating respiratory diseases (such as Pneumonia, Emphysema, COPD, Cold/Flu, Strep Throat, Influenza, Staphylococcus, Pertussis, Chronic Bronchitis and other infections) is plainly evident in many scientific studies. It is an expectorant, helping your body expel mucus. Use it to clean mold and mildew and rid the air of spores. 

It not only fights airborne pathogens but internal pathogens too.


Immune Support

Cineole boosts your immune system and quickens your immune response to pathogens.


Because of it’s anti-inflammatory traits it treats headaches, sinus pressure, ear aches and more.


It is well known to serve skin conditions like rashes, herpes simplex, acne, boils, burns, cuts and wounds. 


Cineole can be an insecticide like a lot of monoterpenes. Clinical studies have shown it is as effective at killing lice as dangerous chemical treatments such as ivermectin.


Cineole allows you to have more restful sleep by increasing the time spent in REM. It slows down and improves neurodegenerative diseases like dementia and Alzheimer’s.

Circulatory System/Liver

Research tells us it can fight severe liver disease and protect your liver from damage by naturally helping your body produce more detoxyfying enzymes. It also is used to treat disorders of the liver. Treatment for POTS has been linked to Cineole.


It helps the smooth muscles not to spasms. Your smooth muscles are your urinary bladder, gall bladder, uterus, bile ducts, ureters, intestines, and arteries. Cineole also helps treat diseases like Multiple Sclerosis and Parkinson’s which are well noted for their muscle spasms.



It can assist with plaque and gingivits. 

Other Uses

Cineole improves Glaucoma and supports eye health. 


Cineole is powerful and is not recommended to be used on babies, children under 10 and the elderly.  Cineole may improve respiratory diseases in some but disturb it in others. It can cause skin irritation and is considered hot. 


Essential Oils High In Cineole

  • -Eucalyptus Globulus (Highest Level of Cineole)
  • -Eucalyptus Radiata (Second Highest Level of Cineole)
  • -Helichrysum
  • -Laurel
  • -Niaouli
  • -Ravinstra
  • -Rosemary
  • -Melaluca (Tea Tree)
  • -Peppermint
  • -Basil
  • -Sage
  • -Camphor

Camphene (Cam-feen)

Camphene is similar to camphor and related to A-Pinene.


Analgesic (Pain Relieving)


It works for airborne and internal virus such as the measles, 



Camphene is highly known for it’s antifungal uses. It has been used to treat fungal infections in all areas of the body like; athletes foot, toe fungus, skin dermatitis, dysentery (intestinal fungal infection) yeast infections and more. 

Cardiovascular System (heart, blood, blood vessels)

The contributions that camphene make it very effective to support the cardiovascular system by lowering blood pressure, reducing triglycerides, lowering plasma cholesterol (bad cholesterol) and ceasing inflammation. It decreases the risk of cardiovascular disease. It can also improve circulation.

Respiratory System

Camphene is a bronchodilator useful for treating COPD, Asthma and Emphysema. Because of it’s antimicrobial/antibacterial features it medicates respiratory conditions, cough and colds. It has been validating to reverse damage caused by smoking and Tuberculosis. 


Decreases the occurrence of spasms and cramps in your muscles.


It has show to eradicate peptic ulcers which are lesions in your stomach or intestines and aide in indegestion. It can also lessen the effects of food poisoning. 


Camphene prevents gingivitis and reduces bad breath.


Research shows a substantial decrease in symptoms of anti-inflammatory diseases such as Crohns, Autoimmune, Arthritis, Gout and Rheumatism.


Relives mentals disorders such as anxiety, depression, stress and hysteria.


It has shown to impede mosquitos when applied topically and lessen the irritation of insect bites.


Essential Oils High In Camphene

  • -Thyme (Very high levels)
  • -Rosemary (Very high levels)
  • -Camphor 
  • -Holy Basil
  • -Lavender
  • -Juniper
  • -Pine
  • -Spruce
  • -Fir
  • -Sage
  • -Nutmeg
  • -Ginger
  • -Valerian
  • -Neroli
  • -Cypress
  • -Citronella
  • -Wild Orange
  • -Bergamot
  • -Lemon

2. Sesquiterpenes In Essential Oils

Sesquiterpenes are the second branch of Terpene Hydrocarbons found in essential oils. They are amazing little chemical constituents that offer incredible therapeutic benefits to a person.

They are broadly

  • -Antibacterial
  • -Antiseptic 
  • -Anti-Inflammatory. 
  • -They also support our glandular tissues and certain organs like the kidneys and liver. 
  • -They are also known to fight cancer by oxygenating our cells, destroying deformed cells and creating an environment where cancer cells cannot reproduce.

Common Sesquiterpenes In Essential Oils

Beta-Caryophyllene (Bey-ta Care-ey-oh-fi-lene)

The first sesquiterpenes I’ll discuss is B-Caryophyllene and let me tell you it is AMAZING!!

B-Caryophyllene travels to the Endocannabinoid System of our brain that is directly responsible for emotions, behaviors, and social interaction among other things. It is highly responsible for our immune system function. In our Endocannabinoid System we have identified 2 main receptors named CB1 and CB2. There are also cannabinoid receptors all throughout the body such as the organs, connective tissues, glands, and immune cells. The Endocannabinoid system helps our brain communicate with the rest of our body like a pathway.

CB1 is the same part of our brain that causes the high effect when using marijuana. 

B-Caryophyllene binds to our CB2 receptors which may be a target for therapy of a wide range of ailments. B-Caryophyllene is found in marijuana/cannabis but does not give the psychoactive high effect that marijuana offers because it binds to the CB2 receptor. 





This constituent is very antibacterial and well known for fighting serious infections like E-Coli, Staph, Strep and Salmonella.

Local Antiesthetic



It slows the growth and prevents cancerous cells. It is however, most efficient when used as a supplement with other cancer fighting drugs like Paclitaxel . 


It also helps your cells function properly by improving mitochondrial function.



It is known as a dietary supplement. It helps with digestive issues like Inflammatory Bowel Disease (IBS). It offers colon support notably ulcerative colitis. Caryophyllene can alleviates nausea and increases metabolism. It also helps with diabetes.

Analgesic (Pain Reliever)

It is known as a highly effective analgesic for different type of pain; acute pain, chronic inflammatory pain and neuropathic pain response (pain that is not from a physical stimuli-phantom pain from a limb amputation for example.) It is highly effective taken internally and applied topically.


It decreases inflammation overall and especially in the brain, possibly reducing the outcome of a stroke.


It relieves stress, anxiety, depression, OCD, PTSD and a variety of other mental disorders. It slows the damage of and prevents damage to the nervous system and brain, especially from diseases like Multiple Sclerosis, Parkinson’s, Dementia, Alzheimers and Cancer. It is a sedative also. It helps your body create endorphins naturally. It oxygenates your brain.



It reduces the stress on your heart and increases circulation.


It reduces the blemishes on your skin and supports your overall skin health. It evens and lightens skin tone.

Immune System

It has immune system boosting properties by supporting our white blood cells.


On a study on rats, it showed to increase their longevity.


It repels mosquitoes, ticks and termites.


Prevents gingivitis by eliminating plaque build up.


Essential Oils High In Caryophllene

  • -Copaiba (Very Very High Levels)
  • -Black Pepper (Very High Levels)
  • -Ylang Ylang
  • -Camphor
  • -Clove
  • -Cinnamon
  • -Oregano
  • -Thyme
  • -Rosemary
  • -Basil
  • -Melissa
  • -Yarrow
  • -Carrot Seed
  • -Ravinstra
  • -Lavender
  • -Helichrysum

Conclusion: The Basics of Essential Oil Chemistry

This was part 1 of a 2 part series on the basics of essential oil chemistry. 

In part 2: Oxygenated Compounds will be analyzed. I hope you have time to read it. 

Understanding basic essential oil chemistry is vital in knowing what essential oil to grab for when an issue arises.  

The most important thing to understand is that quality matters more than anything. The compounds listed above can all be created synthetically in laboratories quite easily. When they are synthesized their potency is not even a fraction of what it is from it’s natural source. 

Here is an example:

Limonene makes up over 90% of orange essential oil. When Limonene is created in a laboratory it is cheaper to make. It is also can be sourced from different materials instead of JUST oranges or citrus leftovers. It can be made like some frankinstein creation….a little carbon from here…a little oxygen from there until bam, it’s all put together to make limonene. 

If I created limonene in a laboratory and bottled it and sold it as orange essential oil it would contain some of the health benefits or orange oil but not all. It also runs a much higher risk of having contaminants because of all the different sources it came from. It can also have the opposite effect or pure, unadulterated limonene. One study comparing synthetic limonene and pure limonene from natural sources showed astonishing differences. It showed that pure limonene from all natural sources shrunk the tumors in rats. Limonene created in the laboratory actually created tumors in the rats. 

Limonene produced in laboratories are often oxidized BEFORE they are even bottled due to the process of creating it. Oxidized oils can cause extreme irritation and/or toxicity to skin, respiratory system and mucus membranes. 



Continue to Part 2 of Essential Oil Chemistry-Oxygenated Compounds

To learn more about essential oil chemistry click here.



These statements are not regulated by the FDA and are not intended to diagnosis, treat, prevent or cure any disease or illness. These statements are no substitute for professional consultation with your personal physician. Consult your doctor before making any changes and/or additions to your health care routine.

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Disclaimer: None of the statements on this website have been evaluated by the FDA. Essential Oils and Young Living products are not intended to diagnose, treat, cure or prevent any diseases or illnesses. Read full disclaimer here.

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