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Aromatherapy: A Basic Guide to the Effects of Essential Oils in the Brain



Aromatherapy: A Basic Guide to the Effects of Essential Oils in the Brain


Author: Erica Igere

Editor: Fahad Hassan Shah


Have you ever had that one English teacher who docks her classroom with essential oils, or have you ever thought, "Hey, why does this smell feel so great?". Maybe it wasn't your English teacher (or any teacher at all). If you experienced this before, perhaps you were just grateful that the room smelled nice. End of story. To understand how something as simple as pounds of lavender and oil combined can do wonders for the brain, read on.


When mixed with base oil, herbs, trees, or flowers make up essential oils, which fall under the umbrella term of aromatherapy². They vary from herbs such as rosemary and mint to woods such as cinnamon and cedarwood². At some point, you may have seen a diffuser humidify the oil or spray it into the air with a spray bottle. That being said, the most common way of using essential oils is through the inhalation route³. Using an example scenario, say you put good old rosemary oil into a diffuser, which will vaporize into pretty white air and enter your nostrils. Within the air are trillions of complex molecules that first contact the end of the olfactory nerve—located under the root of the nasal cavity— and travel to the part of the brain where the olfactory nerve starts, which is located in temporal lobe where the amygdala and the hippocampus are located and where the emotional response of the brain occurs, or limbic system¹¹. The oil molecules will first pass through the amygdala, which is responsible for recognizing whether or not a stimulus is harmful, which then sends a signal to the hippocampus to encode a memory for a smell⁴. These two parts of the brain are a part of the limbic system, responsible for long-term memories, behaviors, and emotional processing¹⁷; The system works in both a positive and negative direction, which is why smelling chocolate cookies can awaken positive memories of a loved one's house or negative ones, such as burning rubber, which distresses 93% of US veterans⁵. Molecules in essential oils work positively with regard to the limbic system and the cells of the body, explained further later.


The next common use of essential oils is skin application. Although doctors don't recommend applying raw essential oil onto your skin (due to skin irritation for many people), the oils contain anti-inflammatory, antimicrobial (fights against pathogens), and even anticancer effects. Specifically, reducing the number of cancer cells¹⁹.


Furthermore, essential oils contain many organic compounds such as ketones, alcohols, esters, amines, and terpenes⁶. Terpenes are essential because they provide the scents and colors of the trees and flowers used to make the essential oils¹² and provide additional benefits, as explained below.


Lavender Oil: Lavender oil contains a type of terpene called linalool¹². Linalool is known as an anxiolytic, meaning it reduces anxiety by releasing GABA neurotransmitters to reduce activity in the nervous system, reducing stress and anxiety. Anxiolytics also work by inhibiting the reuptake of serotonin, making serotonin linger more throughout the body, which is a property of antidepressants⁷. Lavender was used as far back as ancient Rome for scented water²⁰, and in today’s research, scientists have found evidence of increased sleep in rats and reduced depression symptoms¹².


Grapefruit and Lemon: Both grapefruit, lemon, and other citrus fruits, such as oranges, contain high concentrations of limonene (60-95%)⁸. They are found on the skins of these fruits and have properties that remove free radicals that are harmful to the body⁹. Limonene also increases nitrite oxide levels- a neurotransmitter for better mood, sleep, and less anxiety¹⁰. Further studies are being conducted today to explore the potential link for Alzheimer's treatment¹².


Pine Oil: Besides its anti-inflammatory against skin conditions and found in mango and guavas, it also has concentrations of myrcene¹⁴. Myecence is both an anxiolytic and a sedative slowing down activity in the brain, promoting sleep, and reducing irritability¹² ¹⁸. Pine oil additionally contains some amount of linalool and limonene properties providing similar benefits as the other essential oils stated earlier¹³.


Note: It is important to use essential oils safely. For example, if applied to the skin, dermatologists recommend diluting the concentrated essential oil with argan or coconut oil to avoid irritation. Please use essential oils in moderation and have fun exploring the vast world of therapeutic oils and the few oils mentioned above³.


References

10. Anesini, C. (2010, Feburary 28). Limonene exerts antiproliferative effects and increases nitric oxide levels on a lymphoma cell line by dual mechanism of the ERK pathway: relationship with oxidative stress. PubMed. Retrieved July 10, 2023, from https://pubmed.ncbi.nlm.nih.gov/19968502/

16. Buchanan, T., Tranel, D., & Adolphs, R. (2003, September 10). A Specific Role for the Human Amygdala in Olfactory Memory. NCBI. Retrieved July 10, 2023, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC217997/

7. Dos Santos ÉRQ, Maia JGS, Fontes-Júnior EA, do Socorro Ferraz Maia C. Linalool as a Therapeutic and Medicinal Tool in Depression Treatment: A Review. Curr Neuropharmacol. 2022;20(6):1073-1092. doi: 10.2174/1570159X19666210920094504. PMID: 34544345; PMCID: PMC9886818.

5. Florida State University. (n.d.). Retraining reactions to smells | Military Suicide Research Consortium. Military Suicide Research Consortium. Retrieved July 10, 2023, from https://msrc.fsu.edu/funded-research/retraining-reactions-smells

13. He, Q. (2012, July 7). Chemical composition, antioxidant, and antimicrobial activities of essential oil from pine needle (Cedrus deodara). PubMed. Retrieved July 10, 2023, from https://pubmed.ncbi.nlm.nih.gov/22757704/

9. Juber, M. (2022, September 19). Are There Health Benefits to Taking Limonene? Pros and Cons, Dosage Amount, and More. WebMD. Retrieved July 10, 2023, from https://www.webmd.com/diet/health-benefits-limonene

11. Marks, T. (2018, October 10). Aromatherapy for Anxiety - How Does It Work? YouTube. Retrieved July 10, 2023, from https://www.youtube.com/watch?v=zackfqlOwZ4

12. Medical Terpenes. (n.d.). How Terpenes Affect the Brain. Medical Terpenes. Retrieved July 10, 2023, from https://www.medicalterpenes.com/how-terpenes-affect-the-brain/

2. National Center for Complementary and Integrative Health. (n.d.). Aromatherapy | NCCIH. National Center for Complementary and Integrative Health. Retrieved July 10, 2023, from https://www.nccih.nih.gov/health/aromatherapy

18. PRIME. (n.d.). Beta-Myrcene - Prime Alternative Treatment Centers. Prime ATC. Retrieved July 10, 2023, from https://www.primeatc.com/resources/beta-myrcene/

17. Rajmohan, V., & Mohandas, E. (2007, Apr-Jun). The limbic system - PMC. NCBI. Retrieved July 10, 2023, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2917081/

8. ResearchGate. (n.d.). The concentration of limonene in the essential oils from different... ResearchGate. Retrieved July 10, 2023, from https://www.researchgate.net/figure/The-concentration-of-limonene-in-the-essential-oils-from-different-Citrus-species_tbl2_350543873

14. ScienceDirect. (n.d.). Myrcene. ScienceDirect. https://www.sciencedirect.com/topics/medicine-and-dentistry/myrcene#:~:text=Myrcene%20is%20an%20example%20of,juniper%2C%20and%20in%20many%20other

6. Trevelyan, O. (2022, February 25). The Chemistry of Essential Oils. AZoLifeSciences. Retrieved July 10, 2023, from https://www.azolifesciences.com/article/The-Chemistry-of-Essential-Oils.aspx

4. V, R., & E, M. (n.d.). The limbic system - PMC. NCBI. Retrieved July 10, 2023, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2917081/

15. Walsh, C. (2020, February 27). How scent, emotion, and memory are intertwined — and exploited. Harvard Gazette. Retrieved July 10, 2023, from https://news.harvard.edu/gazette/story/2020/02/how-scent-emotion-and-memory-are-intertwined-and-exploited/

3. Wilson, D. R., Cronkleton, E., & West, H. (2019, August 9). How to Use Essential Oils with a Diffuser, on the Skin, in Bath, More. Healthline. Retrieved July 10, 2023, from https://www.healthline.com/health/how-to-use-essential-oils#summary

19. Sharopov F, Braun MS, Gulmurodov I, Khalifaev D, Isupov S, Wink M. Antimicrobial, Antioxidant, and Anti-Inflammatory Activities of Essential Oils of Selected Aromatic Plants from Tajikistan. Foods. 2015 Nov 2;4(4):645-653. doi: 10.3390/foods4040645. PMID: 28231227; PMCID: PMC5224554.

20. University of Iowa. (n.d.). Roots of Medicine. English Lavender – Roots of Medicine. Retrieved July 10, 2023, from https://dsps.lib.uiowa.edu/roots/english-lavender/





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