Essential oils - why do they work?

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Updated - March 30, 2025

Essential oils, why do they work? This question is justified, and the answer is extremely profound and unexpectedly exciting.

Smell - everyone is probably familiar with scented lamps, such as scented candles, whose fragrance is not always perceived as pleasant, but often causes headaches, discomfort and even nausea, especially with synthetic fragrance oils.

Fragrances seduce, not only in the form of a woman's perfume, but also on the train, in hotels, department stores, etc., to put customers in a pleasant state of mind, thus enticing them to make better evaluations or product purchases by diffusing them through air conditioning systems in the premises.

Fragrances are used in hospitals to reduce the use of analgesics (painkillers) or hypnotics (sleeping pills), as well as in palliative care to provide relief for the sick.

The origin of essential oils lies in the immune system of plants, which use them to protect themselves from predators, fungi, bacteria and viruses, i.e. they have an antifungal, antibacterial and antiviral effect. The essential oil of peppermint, for example, is so strong that it would damage the plant itself if it were not packed in small capsules on the leaves, which only release their active ingredient when touched.

Although such applications are now well known and would not be practiced by commercial enterprises in particular if there were no proven efficiency of these economically oriented measures, the question remains: how can this be - what is the basis for this effect in humans?

Smell and taste

We can "smell" someone or rather not ..., remember experiences with grandma, if she was friendly to us, positively, as soon as we perceive e.g. lavender scent, which she used in bags in the closet to protect against moths. However, if grandma was a rather unpleasant person, we quickly leave as soon as we notice this scent, which we now perceive as unpleasant.

Our nose does not always function as an objective olfactory organ and is influenced in its perception of scents by our individual experiences.

Olfactory receptors support the taste buds in the perception of sweet, sour, salty, bitter and savory. Spicy, on the other hand, is not a taste in the true sense of the word, but a pain stimulus that is triggered by e.g. chili, black pepper via their chemical components. Capsaicin or Piperine and caused by the Trigeminal nerve-The pain is transmitted from the facial nerve to the brain, where it is defined as pain.

The trigeminal nerve, which is activated by stimuli to pain, temperature or chemoreceptors, transmits the pain signals to the thalamus, which passes them on to various areas of the brain, including the somatosensory cortex in the parietal lobe (upper part of the skull, located above the occipital lobe and behind the frontal lobe; responsible for the localization of pain and its qualitative assessment, as well as somatosensory perception and hand-eye coordination).

So if pain is to be combated, one could come up with the idea of switching off the trigeminal nerve. However, as the nerve not only processes the sensation of pain, but also heat, cold and chemical stimuli, these functions would no longer exist. We would not perceive a burn or frostbite any more than we would a chemical burn. Perhaps practical, but not sensible.

How do pain receptors work?

Pain receptors are localized on nerve cells and contain ion channels (TRP – Transient Receptor Potential), which are opened and activated by the above-mentioned stimuli.

The cell, which is normally negatively charged compared to its surroundings and therefore at resting potential, is depolarized by an influx of positively charged ions and raised to its action potential.

Exceeding a defined threshold value initiates a signal that is transmitted along the nerve fibers to the brain as a pain stimulus.

Which receptors are relevant?

Trpa1-receptors react to cold and chemical substances (Eucalyptol, cinnamon oil, ginger oil, clove oil (Eugenol)), but are also activated by inflammatory stimuli or tissue damage and cause the brain to signal pain.

Trpv1-receptors react to high temperatures (combustion) or chemical stimuli (Thymol, Capsaicin - ABC plaster), with the same result.

The Trpm8-receptor, on the other hand, is triggered by cold stimuli (< 28 °C), but also by chemical substances such as Mentholwhich also presents itself as a pain stimulus.

A Trpv4-receptor responds to temperatures of 25 ... 35 °C, while Trpv3 for the range 30 ... 40 °C, Trpv1 covers temperatures > 43 °C and Trpv2 > 52 °C.

Pain fights pain?

What sounds absurd at first turns out to be a fact in practice. But how can that be?

On the one hand, the aforementioned pain receptors perform a warning function by alerting the body to dangerous temperatures, conveying corresponding sensations that enable people to take countermeasures.
You will quickly pull your hand off the hot hob or out of a corrosive liquid, put something on if it is too cold, spontaneously hold your breath in the presence of pungent-smelling gases. The body reacts to a "hot" pepperoni or chili pepper with a burning, extremely painful sensation and increased saliva production in order to get rid of the irritant as quickly as possible, and so on.

On the other hand, intense pain stimuli cause the release of the body's own substances, such as Endorphins, enkephalins, serotonin and Prostaglandinsup to opiates. If this release is not stopped because the pain stimulus is still present, excessive and harmful reactions would occur.

This is why the pain receptors switch off after a few minutes and can no longer be stimulated for a while. This also stops the release of the respective substances.

Chemical effect on (scent) receptors

The well-known ABC plaster is known for its burning sensation. Capsaicin activates the Trpv1 receptor. This transmits the heat-induced pain signal to the brain. This in turn localizes the area of the "painful back" and causes the blood vessels there to dilate in order to increase the blood supply and thus dissipate heat, as it is - supposedly - "hot" there.

The therapeutically intended effect of increased blood circulation allows waste products in the hardened, and therefore painful, muscle to be removed more effectively and the muscle to relax again. The effect caused by the Capsaicin induced pain subsides after a while, but the feeling of warmth lasts for several hours.

The "heat" perceived by the brain results exclusively from the Capsaicin-induced chemical Receptor stimulusbut not from actual physical warming.
The perceived "increased" warmth underneath the ABC plaster is only slightly higher than the body temperature itself. This is because the vasodilation increases blood flow and the skin area is therefore slightly warmer than the surrounding tissue, which is less intensively supplied with blood.

Another active ingredient, namely Eugenol from clove oil is known to many contemporaries from visits to the dentist on the occasion of unbearable toothache - the trigeminal nerve sends its best regards ...
Eugenol binds on Trpm8-receptor and thus blocks the transmission of pain stimuli.

Likewise Menthol and Peppermint oil on Trpm8 receptorespecially for chronic pain, as Trpm8 switches off after about 5 minutes and is no longer receptive to further pain stimuli.

Linalool and Linalyl acetateboth main active ingredients of lavender oil, are detectable in the blood after a gentle massage using lavender oil after only 5 minutes (source), just 20 minutes later peak concentrations of 121 ng/ml Linalool and 100 ng/ml Linalyl acetate measurable.

Similarly, inhalation of lavender essential oil atomized by means of a diffuser produces identical concentrations as topical application after percutaneous ingestion, as in the above case.

Both active ingredients have sedative, anxiolytic, relaxing and analgesic effects, Linalyl acetate additional antimicrobial effect.

Olfactory receptors vs. scent receptors

In addition to the nasal olfactory receptors, there are also olfactory receptors (proteins specifically produced by a cell). These are present in all organs, most in the testes (with around 55 active genes out of a total of 138 available), and least in the liver (with only one gene out of a current total of 19).

Since the molecules of essential oils are absorbed percutaneously, inhalationally or internally (oils in capsules) via the gastrointestinal tract and can be detected in the blood, even passing the blood-brain barrier due to their molecular size, it is not surprising that their effect is also found in all organs of the body.

But how exactly does it work?

The cell

Every cell in the human body consists of the nucleus (Nucleus), which contains a complete gene set, to the surrounding cytoplasmin which all cellular processes take place, and the all-encompassing, selectively semi-permeable Cell membranethrough which channel-forming proteins enable the exchange of substances, and receptors located on the cell membrane serve intercellular communication.

DNA (DNA)

The DNA (deoxyribonucleic acid -> Deoxyribonucleic acid) contains the information required for the structure, function and reproduction of all cells and organisms.

Around 98% of the genes are deactivated, only 20,000 ... 25,000 genes are active and are used for the synthesis of proteins.

mRNA

mRNA (messenger RNA) is a copy of the information strand contained in the DNA for the production of proteins, which in turn control functions in the body.

Transcription

Similar to bamboo, which has recurring thickenings in its trunk, there is a beginning (Promoter) and an end (Terminator sequence - This also acts as a switch that turns the gene on or off) of the gene sequence to be read and copied.

To gain access to the section to be copied, the "ladder" must be positioned at the point indicated by the Promoter marked position. This is done with the enzyme RNA polymerasewhich also creates the copy. If the enzyme reaches the Terminator sequenceit stops the copy.

The resulting mRNA molecule separates from the DNA, the separated strand closes again and the mRNA is released from the cell nucleus into the cellular environment. cytoplasm discharged.

Translation

The now in cytoplasm mRNA can now be used as a template for protein biosynthesis during the Translation serve. The translation "translates" into the Ribosomes the previously produced copy of the genetic information of the mRNA into a functional amino acid sequence that develops the intended effect in the body as a protein.

Exocytosis (only for secreted proteins)

In order for a protein that is supposed to act outside the cell, such as Hormones, Enzymes or antibodyit must be transported out of the cell. This process is known as Exocytosis.
The task of transportation is performed by so-called (specialized) Vesicles. The Vesicles fuses with the cell membrane and releases its contents into the Extracellular space.

The GABA receptor

The GABA (GAmma-AminoButyric Acid) receptor is the most important functional inhibitory neurotransmitter. It exists in two variants: GABA_A as a pure ion channel receptor, fast-acting, and GABA_B as a metabotropic Receptor, slower but longer acting.
Metabotropic receptors usually belong to the family of G protein-coupled receptors (GPCRs) and initiate processes through secondary messengers or intracellular signaling pathways.
When a neurotransmitter or another signal binds to such a receptor, a G protein is activated. This triggers a cascade of further biochemical reactions that can influence various cell processes, such as the activation of enzymes or the release of secondary messengers such as cAMP or IP3.

It is the target of many medications, but also of essential oils, when it comes to achieving spasmolytic, anxiolytic effects or basically regulating the excitability of nerve cells.

The effect is due to the influx of negatively charged chloride ions. As mentioned above, an increasingly negative cell potential results in a lowering of the action potential. This is reinforced by substances that bind to the GABA receptor, resulting in calming, relaxing and anxiety-relieving effects.

The protein - the scent receptor

The protein produced by translation serves as a scent receptor. As soon as a fragrance molecule binds to the receptor, it triggers the specific effect via the corresponding signal.

Here is the process described above as a graphic in full:

And how does the fragrance molecule find the fragrance receptor when the human body consists of around 37.2 trillion(!) cells - 37,200,000,000,000,000 when written as a decimal number? How much essential oil is actually needed so that each cell only has a single molecule of essential oil available?

ONE drop

A single drop of grapefruit oil contains 226.92 trillion oil molecules. Divided among the approximately 37.2 trillion body cells (depending on weight and size), there are 6.1 million oil molecules per cell!
This means that no body cell need fear being overlooked by the molecules of a single drop of essential oil.

It should now also be clear that essential oils can reach every organ of the body and therefore influence its function.

Gene - switched on or off

If you examine tissue samples from human organs, you will find scent receptor genes that are switched on and off in the scent receptors. Depending on which genes are switched on or off, it is possible to determine which organ is involved. This means that each cell of the same organ has the same genes activated or deactivated.

The number of genes switched on in the tissue allows conclusions to be drawn about the state of health of the tissue. Compared to diseased tissue, healthy tissue has relatively few genes switched on and only for very short time intervals (paler color marking, see figure below).

An activated scent receptor gene stands for the ongoing production of proteins. The longer it is switched on, the more proteins are expressed.

Diagnostics ...

If significantly more scent receptors are switched on and possibly for a longer time (darker color marking) than usual, this indicates tissue diseases or tumor activity, as shown here as an example in a 21 tissue samples from a Breast cancer compared to 7 healthy samples.

FPKM is a metric for quantifying the expression of genes. It is a normalized measure that makes it possible to compare gene expression between different samples or conditions.

A marker is a substance that only occurs in elevated concentrations or only exists in the first place when tissue is diseased or affected by a tumor.

... Therapy

Prof. Dr. Dr. Dr. med. habil. Hanns Hatt (Ruhr University Bochum (RUB)) has been working for decades in the field of molecular and cellular sensory physiology, smell and taste research, is an author, gives lectures and publishes his research findings such as "Human olfactory receptors: New cell functions outside the nose„.

The above illustration was taken from the document linked above and shows, in addition to many other research results and publications (see references), that essential oils can be used effectively in diagnostics and therapy thanks to the proven existence and activity of the olfactory receptors (OR) located in these tissues.

Practical examples

All theory is gray, here rather colorful, but a few examples from human practice, from life itself, convey more impressively what the theory only presents more or less dryly.

All examples can be found in the presentation "Healing with fragrances" from 04.06.2019, Johannes Gutenberg Foundation, endowed professor Dr. Dr. Dr. med. habil. Hanns Hatt at the Ruhr University Bochum, taken from.

How do sperm find the shortest route to the sperm cell?

Up to 20 of the 53 scent receptors are found in a sperm. In vaginal secretions, there are 15 known scents that guide the sperm (including Bourgeonal; Antagonist: Undecanal)) and lead to a doubling of their locomotion speed. If the sperm are exposed to the antagonist Undecanal exposed, they lose their orientation and reduce their speed again.
There are ten times more olfactory receptors in the cervix than in the olfactory epithelium itself (10 ... 20 million), making it the best-guarded place in the human body.

Gastrointestinal tract

In the gastrointestinal tract there are about 15 ... 20 different scent receptors. By ingestion of e.g. Eugenol (clove as a spice or essential oil), the scent receptor hOR1D2 stimulated, whereupon Serotonin and peristalsis is increased.

Skin and hair

The skin is characterized by keratin-containing cells (Keratinocytes) is kept supple and elastic by keeping the epidermis (epidermis) keratinizes, forms skin scales and is replaced by fresh cells growing from below. There are over 30 scent receptors in the keratinocytes. Sandalore is a synthetic sandalwood fragrance (synthetic because real sandalwood is very expensive), which significantly increases the growth and elasticity of skin cells by increasing the calcium concentration, as well as allowing wounds to heal about 40 '% faster.

It also ensures Sandalore via receptors in hair root cells for a 20 % longer hair life.

Heart

The scent receptor OR51E1 is responsible in the heart for lowering the heart rate and cardiac output, for example.

lung

In the lungs, the scent receptor OR2AG1 with stimulation by Amyl butyrate (Roman chamomile) relaxes the pathologically contracted smooth muscle cells, which is important for asthmatics, allergy sufferers and COPD patients.

prostate

The scent receptor hOR51E2 is expressed in large quantities in prostate cancer cells and serves as a tumor marker. β-ionone (violet scent) reduces the proliferation rate (growth rate). However, there is currently no known way to deliver the scent molecules to the site of action, not even via the blood. (source)

Bubble

In bladder cancer, the olfactory receptor OR10H1 expressed. Stimulation with Sandranol (Santalol), the natural sandalwood oil, inhibits and reduces tumor growth. A urine test allows conclusions to be drawn as to whether bladder cancer is present or not, as dead cells of the inner wall of the bladder are flushed out in the urine. (source)

Colon

The scent receptor OR51B4 is released in the presence of colon carcinoma. The colon carcinoma cells (HCT116) react to the fragrance Troenan (privet), which significantly inhibits tumor growth by altering the cell morphology of colon cancer cells.
(source)

List of all olfactory receptors

The following (excerpted) list of all human olfactory receptors, including all scientific data, is available here is available for download as an Excel file.
The data is taken from The Human Protein Atlas.

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Remark
Research is constantly progressing. The above article does not claim to be exhaustive. If the reader is aware of any facts in this regard with references that have not been mentioned here, please let me know. Notice.

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Sources

Further studies on this topic can be found under the following links, among others:

2024-10-04 – Olfactory Receptors and Tumorigenesis: Implications for Diagnosis and Targeted Therapy
(Summary - full text with costs - 54 references)
Yi Tang ^# 1, Ye Tian ^# 2, Chun-Xia Zhang ¹, Guo-Tai Wang ³

2021-02-05 – The mutational landscape of human olfactory G protein-coupled receptors
(Full text - 66 references)
Ramón Cierco Jimenez, Nile Casajuana-Martin, Adrián García-Recio, Lidia Alcántara, Leonardo Pardo, Mercedes Campillo & Angel Gonzalez

2018-11-30 – Therapeutic potential of ectopic olfactory and taste receptors
(Summary - full text with costs - 317 references)
Sung-Joon Lee, Inge Depoortere & Hanns Hatt 

2018-06.13 – Human Olfactory Receptors: Novel Cellular Functions Outside of the Nose
(Full text - 212 references)
Désirée Maßberg ¹, Hanns Hatt ¹

2009-10-30 – Dual activities of odorants on olfactory and nuclear hormone receptors
(Full text - 74 references)
Horst Pick^‡,1 ∙ Sylvain Etter^‡,1 ∙ Olivia Baud^‡ ∙ Ralf Schmauder^‡ ∙ Lorenza Bordoli^§ ∙ Torsten Schwede^§ ∙ Horst Vogel^‡