Aromatherapy: Part 2 - The Science

Following my last blog "Aromatherapy: Part 1 - An Introduction", you would have a good understanding of what aromatherapy is and how essential oils are used.  Now I'll present some of the science that explains how aromatherapy works. 

 Photo by  Sam Manns  on  Unsplash

Photo by Sam Manns on Unsplash

Aromatherapy is a form of plant therapy. In the English system (the one I am trained under, as are most aromatherapists in Australia) essential oils are administered mainly via inhalation methods, massage, compresses and other diluted skin application methods (face and body oils, balms, lotions, etcetera).  In the French system (known as aromatic medicine) it is administered internally, topically - neat, by inhalation and by compresses.  The French system requires more training as ingestion of oils and neat application is more risky and you require a deeper understanding of how the oils interact biochemically. Thus why I get frustrated when MLM companies tell people who are not aromatherapists that they should ingest essential oils. Essential oils are highly potent plant medicine and, like with any medicinal/therapeutic substance, there are safety concerns. Unfortunately the industry is unregulated so there is nothing to stop different corporations from providing superficial information and taking no responsibility for their customers health. This is in extreme contrast to when you see a health practitioner - we are trained to ensure we apply our knowledge and skills to not cause any harm, and to help our clients reach a state of better health. 


Pathways - how essential oils enter the body

There are three main pathways for essential oils to make their way into the body to have a therapeutic effect. These are:

  1. Inhalation - via the nose;
  2. Topical/Absorption - via the skin (including massage, lotions, perfumes, skin care products, etc.); and
  3. Internal application (oral intake, pessaries, and suppositories). I won't be discussing internal application. 

PATHWAY 1: INHALATION - NOSE

Inhalation of essential oils is the best way to assist with emotional problems such as stress, anxiety and depression as it reaches the limbic system in the brain quickly. Inhalation also enables essential oils to travel down to the lungs, allowing them to help with breathing difficulties or illness in the respiratory system. In addition, essential oils will reach blood circulation this way - being absorbed via the mucous linings of the respiratory system and entering gaseous exchange in the alveoli of the lungs - thus transferring to blood. From there they can also circulate to cells in the rest of the body. 

The Olfactory System

Olfaction (smell) works via chemoreceptors. The sense of smell helps us to taste and enjoy food. In fact, if you lose your sense of smell (anosmia) food will taste very bland because these senses are intrinsically linked and 80% of taste actually comes from smell. Smell also warns us of danger - e.g. smoke (fire) or enables us to tell if our food has gone bad. Generally nice smells really do make life more pleasurable - the smell of food, flowers and essential oils all help to enrich our life.

The olfactory pathway is as follows:

 Courtesy encyclopedia.lubopitko-bg.com

Courtesy encyclopedia.lubopitko-bg.com

  1.  For a scent to reach the brain it needs to be volatile (essential oils are). Vaporised odour molecules enter the nostrils and many of these molecules reach the olfactory epithelium. 
  2.  Within the olfactory epithelium there are approximately seven million olfactory receptor neurons (which explains why our sense of smell is able to detect thousands of different odours). There are cilia projecting from the receptor neurons. The odour binds to odourant receptors on the cilia of the olfactory sensory neuron. It is believed that the cilia does not move, but rather the mucous moves along the cilia and propels the odour along.
  3. The olfactory receptor cells gather in bundles and project through the cribriform plate of the ethmoid bone reaching the olfactory bulb (which is part of the brain and is located against the cribriform plate).
  4. There are neurons within the olfactory bulb called glomeruli, and each glomerulus is sensitive to a particular odour molecule. The odour molecule will synapse with it's corresponding glomerulus. An essential oil is actually made up of several chemical constituents which determine its odour. It's chemistry!
  5. The olfactory messages are initially processed in the olfactory bulb (glomeruli) and then sent to the higher olfactory areas of the brain. The different targets in the brain are involved in olfactory discrimination, perception and memories as well as olfactory signals that activate smell-related emotions and behaviours (i.e. the limbic system of the brain).  

The Limbic System

The forebrain is the largest portion of the brain and consists of the two cerebral hemispheres (left brain, right brain) and also contains the limbic system. The limbic system consists of many parts. These parts control integration of information from our senses, voluntary movement, higher abstract thought, logic, speech and emotions. The limbic system establishes emotional states (happiness, fear, anger) and links to both conscious responses such as movement, as well as autonomic (unconscious) functions including hormones. It also facilitates memory storage and retrieval. 

The limbic system is stimulated by all of our senses, however the olfactory system (sense of smell) has only one synapse to reach the brain and then another synapse to assert its influence on the limbic system, opposed to all of the other senses which have a minimum of three or four synapses, and therefore the olfactory system has greater power to instantly influence the limbic system. 

Some Parts of the Limbic System and their Functions

 www.freepik.com/free-vector/hand-drawn-infographic-template-of-brain_1001474.htm - Designed by FreepiK

www.freepik.com/free-vector/hand-drawn-infographic-template-of-brain_1001474.htm - Designed by FreepiK

Thalamus: is involved in detecting and relaying information from our senses. It takes in many things that you are not consciously aware of but sends what it deems "important" to the cortex - where you make decisions.

Hypothalamus: controls the secretions of the pituitary gland which produces the most important hormones of the body which influence appetite, sleep-wake cycle (the circadian rhythm), thermoregulation and attraction/reproductive impulses. It regulates the autonomic nervous system, which consists of: the sympathetic (the stress response) and the parasympathetic (relaxation response).  

Amygdala: is involved with anger, violence and anxiety. It’s designed to help us get out of harm's way. Output from the amygdala can go to the pre-frontal cortex or to the hypothalamus – affecting heart rate, breathing rate, hormones, etcetera. Interestingly people with PTSD have a larger amygdala – periods of significant stress cause neurons in the amygdala to grow more dendritic processes.

Hippocampus: involved in memory processing. Converts short-term memory to long-term memory. Memories are related to emotions. The memories aren’t stored here, but the hippocampus replays memory to the cerebral cortex to form long-term memory. It also plays a role in turning off the stress response. People with long-term clinical depression will have a smaller hippocampus as it will slowly atrophy over time. So long-term emotional states can affect the cells in the brain.

Aromatherapy and the Limbic System

The limbic system is primarily involved with emotional responses and therefore inhalation of pure essential oils will usually improve mood. Importantly, the scent should be pleasing to a person to have the desired positive effect. Essential oils will affect our emotions in different ways, depending on the chemical constituents they are comprised of.

Scent will also affect our mental state - some essential oils are known to be stimulating and increase our alertness, other essential oils will sedate us, whilst others have an adaptogenic (balancing) affect - meaning they may be a stimulant or sedative depending on the quantity used and what state the person is in. 

 Photo by  Amy Treasure  on  Unsplash

Photo by Amy Treasure on Unsplash

Note that scent has a powerful influence on memory - we tend to store the memory and the scent together - so a scent can actually trigger a memory and an emotional response. Therefore an aromatherapy treatment needs to be tailored to the individual. For example for most people true lavender oil will produce the relaxation response – it is made up of chemical constituents that calm the nervous system. However if a person was close to their grandmother who has passed away, and she usually smelled of lavender, this scent could trigger the memory of her and produce feelings of grief instead of calm. So an aromatherapist will work with the client to choose essential oils that the client will find pleasing to them. After all there are many great essential oils that calm the nervous system so another essential oil would have a better outcome in this example. 

PATHWAY 2: ABSORPTION THROUGH THE SKIN

Evidence of Skin Permeability

The skin is semi-permeable, which means that most chemicals are absorbed to some degree. Therefore I would recommend you minimise use of pesticides (which are lipid like and can get through the skin), harsh cleaning products (which is basically most cleaning products), as well as skincare products and cosmetics containing unnatural ingredients (which again, is most products). There are natural and earth friendly alternatives to every product. Once a substance/chemical makes it through the skin it easily penetrates the cells in the human body because of the presence of lipids in cell membranes. For example, in the 1970's the chemical hexachlorophene was used as an antiseptic in baby soaps and talcum powders which caused brain damage and death in some babies, proving that the product was absorbed into the skin and therefore reached the cells of the body.

How Essential Oils Penetrate the Skin

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Essential oils are made up of natural chemical constituents - meaning they are unaltered from nature. Essential oils are lipid (fat) soluble and penetrate the skin via the stratum corneum - the outermost layer of the epidermis and via the hair follicles and sweat glands. The stratum corneum is comprised of lipophilic cholesterol, cholesterol esters and ceramide - meaning that fat-soluble substances will absorb faster and more easily into the epidermis. Essential oils are also light in molecular weight which means they are more readily absorbed into the skin. Skin permeability is generally increased with heat (e.g. massaging the skin and warm environments), skin hydration (a bath or shower), the particular carrier oil used (some vegetable oils penetrate the skin easier than others - e.g. sweet almond oil will penetrate more easily than olive oil), and other factors such as the integrity of the stratum corneum or the use of occlusions (e.g. a dressing/bandage or a mask). Once essential oils have penetrated the epidermis they will pass through the dermis and reach the local capillaries and therefore the bloodstream. From the circulatory system they can reach the rest of the cells in the body. 

One advantage of essential oils being applied to the skin (diluted in vegetable oil) is that they are not subject to immediate metabolisation by the liver (as they would be if taken orally).

When applied to the skin during massage, most essential oils will be detected from exhaled air within 20 to 60 minutes, showing that skin penetration is fairly fast. However some enter the skin more readily than others. Therefore when receiving an aromatherapy massage it is beneficial to book in for a minimum of a one hour massage. This will also help the client to reach a state of complete relaxation. Massage increases circulation and raises the local skin temperature slightly which is likely to increase absorption. During massage, some of the essential oil blend will also be inhaled and the aromatherapist may be diffusing essential oils in the room, for further benefit.

Essential oils easily penetrate the skin in bath water - and are also inhaled with this application method. Other skin application methods include roll-on natural perfumes, compresses, sprays, and face/body oils, creams, lotions and balms. Essential oils will then be excreted via the kidneys/bladder, large intestine, lungs and to some extent the sweat glands. 


Essential Oil Chemistry  

The chemical constituents that comprise an essential oil determine its therapeutic value (and scent). Essential oils can assert influence and be of therapeutic value on the endocrine (hormonal) system, the immune/lymphatic system, digestive system, muscular system, integumentary (skin/hair etc.) system, respiratory system, cardiovascular/circulatory system, nervous system, reproductive system, urinary system and skeletal system. Usually there are no unwanted side-effects from using essential oils, provided they are used appropriately, and the right essential oils are chosen. For example, you wouldn’t want to use cinnamon oil on the skin because it is a known dermal irritant, however for inhalation purposes it is wonderful when you have a cold and it has warming affects on the body. It is a stimulating oil and will support the immune system as well as stimulate circulation and digestion. 

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The chemical constituents will determine different therapeutic effects such as: antiseptic, antibacterial, analgesic (pain relief), anti-fungal, anti-inflammatory, antitoxic, antiviral, antipruritic (relieves itching), anti-seborrheic (prevents production of excessive sebum/oil), anti-rheumatic, antispasmodic (eases spasms), cardiac (stimulates heart), cephalic (stimulates/clears mind), calmative (tranquillising effect), carminative (settles digestive system), deodorant, digestive, diuretic, energising, cholagogue/choleretic (increases bile), cicatrisant (wound-healing), cytophylactic (encourages growth of skin cells), decongestant, depurative (purify body/blood), disinfectant, emmenagogue (regulates menstrual flow), expectorant (expels mucous - treats coughs), galactagogue (increases milk secretion), hepatic (stimulates/aids liver function), insect repellent, mucolytic (breaks down mucous), nervine (strengthens/tonifies the nerves), oestrogenic (stimulates oestrogen), rubefacient (warming, increases blood flow), sedative, spasmolytic (relieves smooth muscle spasm), vulnerary (prevents tissue degeneration). There are more, but this is enough to get a good understanding of therapeutic actions. 

Just one essential oil will be composed of several chemical constituents but there will be a few dominating ones and this is what aromatherapists take into consideration when choosing oils for their therapeutic action/s. For example, some essential oils are great for the skin – such as German chamomile. It has an anti-inflammatory action used topically and this is due to it’s chemical constituents – one being chamazulene. It also speeds wound healing. German chamomile has many affects on the body but when I think of it, I immediately think of it as being one of the best oils for the skin. So if I wanted to treat eczema or another skin condition, I’d consider using German chamomile in the blend and choose the appropriate treatment method – such as providing the client with a blend in a soothing vegetable oil to be applied to the skin daily.

Here are some further practical examples. 

Bergamot oil is mainly composed of limonene, linalool, and linalyl acetate. These make this essential oil an analgesic (pain reliever), antidepressant, antiseptic, antiviral, calming, good for digestion, deodorant, and cell-regenerative. Bergamot is an excellent oil to uplift the mood whilst having a calming affect so if a person is feeling anxious a relaxing full body massage with bergamot and some other calming oils would be very helpful.  You can use it at home in a diffuser to uplift the mind and calm the nervous system. 

Carrot Seed oil is naturally comprised mostly of a-pinene, B-pinene, carotol, and many other constituents. It is a natural source of vitamin A. It is great to use in skincare products as it is a cellular regenerator. It is recommended (diluted) for skin problems such as rashes, skin irritation, and dermatitis and helps aged skin and wrinkles. I'm utilising this essential oil in some of the face oils I'm currently creating. 

Clary Sage oil is mainly comprised of linalool, linalyl acetate, caryophyllene, a-terpineol, geraniol, neryl acetate, sclareol and germacrene D. Clary sage is an antidepressant, antispasmodic, deodorant, emmenagogue, nervine and sedative. This is one of my favourite essential oils for helping to balance my hormones and make me feel happy and relaxed. It is considered a euphoric. It is great for treating anxiety, stress and depression. It calms the mind, yet uplifts the mood, making it a balancing oil. It should be avoided during pregnancy (because of its oestrogenic action), however it can help with labour - reducing anxiety and tension. This is an essential oil I believe every woman should utilise because it is beneficial for PMS, menstrual cramps, promotes menstruation when it is delayed, and helps with menopause. It is also used in skincare for oily skin as it regulates sebum production, and for preventing excessive sweating.

 ESSENTIAL THERAPEUTICS ESSENTIAL OILS. TGA listed and a trusted australian brand. these are THE ESSENTIAL OILS I USE IN MY treatments,  my products (face oils & natural roll-on perfumes), AND SELL directly TO MY CLIENTS. 

ESSENTIAL THERAPEUTICS ESSENTIAL OILS. TGA listed and a trusted australian brand. these are THE ESSENTIAL OILS I USE IN MY treatments,  my products (face oils & natural roll-on perfumes), AND SELL directly TO MY CLIENTS. 

Roman Chamomile is my favourite essential oil. I find it helpful if I've had a tough week and want to melt my stress away in an aromatherapy bath. Sometimes I just use some epsom salts and roman chamomile in the bath - I love the aroma so much and find it calms me and makes me feel good. The chemical composition does tend to vary a bit (depending where it comes from and natural conditions when harvested). The main chemical composition is: a-pinene, b-pinene, sabinene, 1,8-cineole, caryophyllene, and propyl angelate and butyl angelate. This oil is an analgesic, antiseptic, calming, good for digestion, emmenagogue, sedative, antidepressant among many other things. It is a good essential oil to use on children because it is quite gentle. I often include it in blends to help with women's hormonal issues including PMS, amenorrhoea (failure to menstruate for over three months) and dysmenorrhoea (painful periods). 

True Lavender oil has got to be one of the most widely used essential oils because it has so many benefits whilst being quite gentle and healing for the skin. It's good for acne, dermatitis, eczema, psoriasis and wounds. True lavender is compromised of many chemical constituents, with the two main ones being linalool, linalyl acetate plus smaller amounts of a-pinene, limonene, 1,8-cineole, cis-ocimene, trans-ocimene, 3-octanone, camphor, linalyl acetate, caryophyllene, terpinen-4-ol and lavendulyl acetate. The synergy of its components is what makes its use so diverse. Lavender is antiseptic, and analgesic and promotes rapid healing of the skin. It is really good for burns. I've used it many times when I've burned myself cooking.  Lavender oil is one of the best oils for the nervous system - it helps relieve stress. It is a harmonising oil so can be calming or stimulating depending on your body's needs (and the dosage used). It is excellent for insomnia. It is also good for headaches and migraines. Lavender can also assist with women's hormonal issues such as PMS or menstrual pain. French lavender is often adulterated as more is sold than is actually produced so as with all essential oils, I'd recommend purchasing it from a reputable company. 

Aromatherapy is great because it really delights the senses. So it can be used as a healthy substitute for other substances people can rely on to calm them down such as food or alcohol. 


Scientific Research: Evidence-based approach

I'll freely admit that as a natural medicine practitioner for me my collection of anecdotal evidence (clients advising me that they feel better following massage, and the changes they experience following treatment - better sleep, pain gone/reduced, hormones normalising, feeling calmer, more energy, etcetera) is strong - it supports that what I do helps people. However it isn't considered scientific. Scientific research takes on a formal approach with double-blind clinical research being favoured.

Unfortunately, there is not a lot of funding given towards scientific research of natural medicines. Pharmaceutical companies have endless pockets to fund their own trials. Consequently aromatherapy cannot compete with allopathic medicine research - however there is still research being done and in increasing amounts, as some people acknowledge how dangerous some drugs can be and the many side-effects, and search for better options. This is important because I am of the opinion that there are natural medicine approaches (whether complimentary medicine or alternative medicine) to help with any health condition on this planet - and we need to understand which are the most helpful remedies so that integrative medicine can keep growing, and also be tailored to the individual. 

Here are the outcomes from some of the essential oils research. This is by no means an exhaustive list:

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  • Many essential oils do have strong antimicrobial, antiviral, antibacterial, and antifungal properties - and were shown to kill many viruses, bacteria and fungal infections. 
  • Lavender oil is highly sedative and does improve sleep for insomniac patients. However in high doses it can have the opposite effect - and be quite stimulating!
  • Peppermint oil was found to be effective for treating headaches (as an analgesic), just as much as conventional drugs.  
  • Tea tree oil has been shown to reduce acne for some patients - most likely because of its antibacterial properties. Other essential oils have also been helpful.
  • Clary sage was shown to reduce anxiety and stress. 
  • In some trials, aromatherapy massage helped improve quality of life for cancer patients - improving pain, nausea, mood and constipation. 
  • The autonomic nervous system is affected by essential oils. In one trial rose oil and patchouli oil decreased adrenaline and other sympathetic nervous system activities while other essential oils increased sympathetic activity, confirming that essential oils can be calming or stimulating. 
  • Aromatherapy can reduce pain - for example there was research conducted on people with fractured limbs. The aromatherapy group, inhaling sweet orange oil, experienced a reduction in pain when compared to the control group.
  • Aromatherapy does help with menstrual cramps (dysmenorrhea) - specifically, clary sage, lavender and rose were tested and found to be effective. 

There is a lot more research - I've just included some that I've recently read. Clearly, more scientific research is required for aromatherapy to be recognised more by medical doctors, even though those of us practising it or even people using it at home can attest to it's value. 

Research Inconsistencies

While some trials show great improvement for patients receiving aromatherapy massage, there have been a few trials that indicated not much difference in mood after aromatherapy massage - however it is important to note that we don't know under what circumstances the treatment was applied - cold room, noise, uncomfortable bed/table etcetera (i.e. the hospital environment). More importantly, I believe the client-therapist relationship is really the most important thing when receiving a massage. If the client doesn't feel completely comfortable with the therapist then their anxiety/stress levels will not drop enough to produce measurable results. Naturally, with every research trial different therapists will be involved and with many of the trials chances are they didn't even use aromatherapists. So when I see research that doesn't support aromatherapy massage I tend to think that perhaps the people administering treatment weren't doing a good job or did not take time to build rapport with the client/patient. Yes I am biased, but I wouldn't be in this field if I didn't whole-heartedly believe in it. 


Conclusion

In conclusion, essential oils enter the body via the nose and skin and spread to the cells in the body via the circulatory system. Essential oils affect the limbic system in the brain directly, where they can influence state of mind, mood, memory and hormones. Every essential oil is made of different chemical constituents which assert their influence on different systems of the body. Knowledge is required to know which essential oil to use for what condition and how it should be applied. There is research supporting aromatherapy plus countless forms of anecdotal evidence collected by individual aromatherapists. Aromatherapy does have a strong scientific basis, but isn't recognised enough by mainstream medicine and more research is required to gain more recognition. There is also a lot of misinformation circulating, which is damaging to the industry. Therefore I would always recommend you purchase essential oils from an aromatherapist and get real in depth advice on using the essential oils to gain maximum benefit, and advice on how to use the essential oils safely. Remember if you support a company that is unethical, they will continue to gain power. If you support individuals who are doing the right thing, they can make a living and be valued for their many years of continued education, and this will benefit the local economy and local clientele. 

Essential Oils

Living in Brisbane and interested in purchasing essential oils or booking an aromatherapy massage with me? Please contact me on 0433 523 678. If you would like a products price list sent to you, please email: info@essentialrestorativemassage.com.au. I sell other products too, including French clays, epsom salts, organic detox teas, custom face oils and roll-on perfumes. 


References

Battaglia, S (2003). The Complete Guide to Aromatherapy (second edition), Brisbane, Australia: The International Centre of Holistic Aromatherapy

Price, S, Price L. (2007) Aromatherapy for Health Professionals (third edition), China: Elsevier

Worwood, V, (1990) The Fragrant Pharmacy: A complete guide to aromatherapy & essential oils London: Macmillan London Ltd

Useful Resources

There are some good aromatherapy research articles on the website of the National Association for Holistic Aromatherapy (NAHA - American)

You can find more research articles here the National Center for Biotechnology Information (American).

For a visual overview of the limbic system, I recommend you check out this YouTube video.

If you wish to know more about the limbic system, see this lecture by Robert Sapolsky. He doesn't discuss aromatherapy, however this information is interesting and certainly has implications for aromatherapy (at least from my perspective). 

If my explanation of smell went over your head, or bored you, check out this Crash Course clip on YouTube for an understanding of smell and taste, in just 10 minutes! 


Information provided by Essential Restorative Massage is not intended to be a substitute for medical advice, diagnosis, or treatment. If you have a health condition or symptoms of one, please consult with your doctor before using complimentary remedies and therapies.

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