Most massage therapists are familiar with aromatherapy—the art and science of using aromatic plant extracts for physical, mental, emotional, and spiritual well-being. Many of us use essential oils in massage lubricants for physiological effects that help us reduce muscle tension, ease musculoskeletal pain, and aid relaxation responses. In this article, we’ll sharpen our focus and discuss the use of essential oils to improve client mood, shift emotional states, and promote psychological equilibrium.

Mechanisms that Cause Psychological Effects

Essential oils help us achieve psychological session goals through olfaction (the sense of smell), and the aromas’ effects on the central nervous system,¹ their influence on the amygdala,² their ability to change brain chemistry,³ and their euphoric properties.⁴ Other psychological effects of essential oils exist, but here we’ll focus on these primary mechanisms, understanding that psychological effects are often overlapping and complex.

Olfaction

When you inhale the aroma of your coffee, crush a sage leaf between your fingers to cook, or smell lilac blossoms in the spring, you are experiencing the earliest sense. Before our single-celled ancient ancestors could see, hear, or touch, they could smell.

At the top of each inner nasal cavity is a patch of mucus-covered tissue called the olfactory epithelium. Odor molecules dissolve into the olfactory epithelium when we inhale or pass through the throat when the tongue pushes air to the back of the nasal cavity when we chew or swallow.

Though only a few centimeters wide, the olfactory epithelium contains more than 100 million olfactory receptor cells.⁵ We literally dangle exposed nerve endings into the vast ocean of air eddying inside our nasal cavities and fish for aroma information as smells drift by on air currents.

Each olfactory receptor has a different shape that allows it to grab hold of a particular type of aroma.⁶ One receptor hooks spicy aromas while piney aromas float free. Another receptor hooks flowers and vanilla. Others, coordinating their findings, net the complicated chemical odorants that compose the aroma of your massage lubricant. There are approximately 400–450 different olfactory receptors that allow us to differentiate between approximately 1 trillion different odorants.⁷

The Limbic System

Neurons from olfactory receptors bundle together to form the olfactory nerve, which travels to the olfactory bulb (the main organ of smell). From the olfactory bulb at the base of the brain, signals travel to the limbic system triggering olfactory responses.

The limbic system is a group of brain structures responsible for adrenaline flow, emotion, behavior, motivation, long-term memory, and olfaction.⁸ The amygdala, as part of the limbic system, is the integration center for emotions, emotional behavior, and motivation. It is responsible for recognizing the emotional significance of events in the external world and supporting an appropriate behavioral response. The hypothalamus links the nervous system to the endocrine system through the pituitary gland. It triggers parts of the endocrine system to start or stop producing certain hormones.

Aromas trigger olfactory responses in these brain structures. For example, since early times, the smell of fire alerts us to potential danger and triggers the fight-or-flight response. Likewise, the variation in the aroma of a particular food item lets us know it’s rotten and we shouldn’t eat it.

Synchronized menstruation in women is caused by an olfactory response, as are physiological changes and behaviors that arise from pheromonal cues. Pheromones are chemical factors that trigger a social response in members of the same species.

Researched Effects of Aromas

A large body of research demonstrates that aromas positively affect stress levels, cognitive processes, brain chemistry, behavior, perception, and emotional states. For example, changes in skin potential levels (which indicate a person’s level of arousal) demonstrate that jasmine essential oil stimulates (increases a person’s level of arousal). German chamomile essential oil sedates (decreases a person’s level of arousal).⁹ Studies that show rats take longer or shorter times to perform tasks after inhalation of particular plant essential oils indicate that lavender, rose, and valerian are sedatives (slow performance), while lemon, basil, and rosemary are stimulants (increase performance).¹⁰

In one study, there was an increase of cerebral blood flow in humans after inhalation of 1,8 cineol that led to increased efficiency and precision on the work performance of office staff.¹¹ Oils high in 1,8 cineol seem to increase mental clarity and cognitive processing. Significant amounts of 1,8 cineol occur in eucalyptus, rosemary, and bay laurel essential oils.¹²

Research also demonstrated that the inhalation of rosemary, lemon, basil, and peppermint essential oils caused the release of noradrenaline from the locus coeruleus, resulting in reports of increased energy from test participants.¹³ Numerous studies on peppermint essential oil demonstrate that it promotes alert mental states, enhances the sensory pathway for visual detection, allows people more control over their allocation of attention, and increases word learning and recall when used in grade school classrooms at ambient levels (below conscious detection).¹⁴ In a study to show that scent impacts social relationships, people in photographs received higher “attractiveness ratings” when the test subjects were exposed to a pleasant aroma.¹⁵

Lavender, Roman chamomile, German chamomile, and sweet marjoram have been found to sedate the body and decrease stress because they stimulate the raphe nucleus, a part of the brain that causes the release of serotonin.¹⁶ The use of ambient lavender essential oil led to increased sleep and better waking moods in psychogeriatric patients under long-term treatment for insomnia in various studies.¹⁷ And ambient sweet marjoram improved the quality and amount of sleep people experienced. Over time, its regular use helped balance sleeping and waking patterns.¹⁸

Important Notes About Essential Oils

The plant extracts used in aromatherapy include essential oils, essences, absolutes, hydrosols, and CO2 extracts. Each of these products is technically different. However, for ease of communication, we’ll use the term essential oil throughout.

Using the correct botanical species in aromatherapy is important but can prove confusing for novice aromatherapists. Here, I’ll use the common name for clarity. Please cross-reference the common names to the correct botanical names on page 56.

Synthetic, human-made oils (see What are Synthetics? on page 62) are often sold as natural essential oils or added to essential oils to stretch their volume. Unfortunately, other types of adulterations also occur (see Adulterations on page 62). Always use a reputable aromatherapy supplier.

Botanical Names and Psychological Effects of Aromatic Plants

Massage Lubricant

To make a massage lubricant, combine 1 ounce of plain massage cream, lotion, or expeller-pressed vegetable oil with 12–24 drops of a synergy. Avoid creams and lotions with dyes, fragrance, mineral oil, or lanolin. If you opt to use vegetable oils as your carrier, choose organic expeller-pressed oils. For example, sunflower oil and avocado oil have a nice consistency.

Aroma Mist

To make an aroma mist, combine 12–24 drops of an essential oil synergy with 1 ounce of distilled water in a bottle with a fine-mist top. Then, add 1 tablespoon of grain alcohol (e.g., vodka) to give the formula a little added sparkle. You might also add 3–6 drops of a particular synergy to an electric diffuser running in your session room. If you want to make larger quantities, just double the drops and the carrier product. Spritz aroma mists in a high arch over the client when they are in the supine position. Don’t treat the client like a windshield and spray them directly with the mist. Mists used at the end of the session fill the room with aromas clients can enjoy as they dress for departure.

Adulterations  

Adulterations occur when people add alcohol, vegetable oil, synthetic human-made chemicals, or cheaper essential oils to the primary oil to increase its volume and improve profit margins.

For example, melissa (Melissa officinalis) plants contain very little essential oil. It takes a lot of melissa to get a little bit of oil. As a result, producers toss a variety of other plants into the distillation unit along with melissa to get more oil. Another example is lavendin (Lavandula x intermedia), which is easier and cheaper to grow than lavender (Lavendula angustifolia) and smells somewhat similar. Lavendin is often labeled and sold as lavender. Synthetic formulations are regularly sold as pure, natural essential oils or mixed into pure oils to increase their volume or standardize their aromas. The term therapeutic grade is not regulated and so is meaningless. Don’t be fooled by this label.

What are Synthetics? 

Synthetic aromas are odors made by chemical synthesis through human-directed processes. Most fragrances in perfumes, body care products, hair care products, candles, air fresheners, detergents, and household cleaners are synthetics or composed of a combination of natural and synthetic aromas. Companies adding fragrance to products or using plant compounds for industrial purposes have little stake in the purity of plant oils so long as they meet basic standards.

Companies adding fragrance to cosmetics or body care products need the aroma of their products to smell the same every time consumers purchase them. Different growing environments or conditions during a particular growing season can cause even the same species of plant to produce significant variations in the chemistry of its essential oil.

To obtain standardized scents, even companies claiming to be natural and organic may add synthetics or isolated aroma chemicals to natural oils to get a consistent fragrance in their products. In fact, aromatherapy comprises only 5 percent of the international market segment for consumers of essential oils. While there are good reasons for creating synthetic aromas for the perfume industry, like preserving plant species, synthetics have no place in aromatherapy because aromatherapy aims to improve wellness. Synthetics are harmful to people, causing everything from headaches and nausea to allergies and skin sensitivities, and knowledgeable aromatherapists avoid them.

Psychological Effects in the Session Room

Essential oils applied in massage lubricants or diffused in the session room help the body rest and recover while allowing time for reflection. Changes in mood, emotion, and the sense of connection with the natural world enhance the client’s perception of the massage while causing psychological shifts that can have a lasting impact. Let’s discuss some key psychological effects of essential oils.

Amygdala Soothers

The amygdala is an almond-shaped set of neurons located in the medial temporal lobe of the brain. As discussed previously, it is part of the limbic system and associated with fear responses and pleasure. Anxiety, autism, depression, posttraumatic stress disorder, and phobias correspond to abnormal functioning of the amygdala.

Psychologists call the amygdala the brain’s smoke detector. It is constantly on the lookout for smoke—in other words, anything that might be scary. When the amygdala detects something scary, it pumps stress hormones into your body, causing you to fight, freeze, fly, or feel emotionally triggered. So, an amygdala constantly bombarded with scary stuff becomes hypervigilant and begins to view more and more stuff as dangerous.

Inhaled valerian, lavender, and rose reduce the hypervigilance of an overactive amygdala. Use these essential oils in inhalations to counter fear and anxiety responses.¹⁹ While more research is needed, other essential oils, including the euphoric essential oils we’ll discuss later, also produce this effect.

Antidepressant Essential Oils

Non-clinical depression is a normal reaction to painful life events. It’s considered an adjustment condition rather than true depression. For people going through significant life transitions, non-clinical depression causes feelings of sadness, fear, hopelessness, and dejection. Essential oils with antidepressant effects counter low moods, episodes of sadness, mental and emotional fatigue, or apathy caused by distressing situational changes such as the breakup of a relationship or losing a job. Essential oils with this effect include basil, bergamot, clary sage, frankincense, geranium, grapefruit, jasmine, mandarin, melissa, neroli, petitgrain, rose, sweet orange, sweet marjoram, and ylang-ylang.²⁰

Neurosedatives

Neurosedatives are agents that sedate the central nervous system to produce relaxed mind states. Neurosedatives act on the brain by increasing gamma-aminobutyric acid (GABA) levels, triggering GABA receptors, or inhibiting excitatory neurotransmitters.

GABA is the primary inhibitory neurotransmitter in the central nervous system. When GABA levels are high, we feel sleepy and relaxed. Valerian root essential oil is a powerful neurosedative that acts directly on GABA receptors to produce its well-known sedative and tranquilizing effects. Helichrysum is milder than valerian in its neurosedative actions. It causes a gentle increase of GABA levels for a calming effect.²¹

Lavender and melissa act on excitatory neurotransmitters causing mild sedative, antianxiety, and emotional balancing effects.²² Other essential oils with neurosedative properties include Amyris, Atlas cedarwood, bitter orange, German chamomile, hops, hyssop, lemongrass, linden flower, mandarin, neroli, Roman chamomile, rose, sandalwood, spikenard, and sweet marjoram.

Neurostimulants

Neurostimulants are agents that stimulate the central nervous system to produce alert mind states. They work by causing an increase in cerebral blood flow, by increasing beta wave activity in the brain, by stimulating the locus coeruleus (the area of the brain associated with the flow of norepinephrine), and by blocking GABA receptors.²³

Norepinephrine plays a vital role in focusing attention, increasing mental alertness, and forming and retrieving  memories. High levels are associated with the fight-or-flight response. Some neurostimulants block receptor sites for GABA, reducing GABA activity on the brain and improving alertness and attention.

Neurostimulants are a good choice when people are emotionally exhausted, dealing with burnout, experiencing brain fog, or have low mental energy. They are potent when used in an aroma mist (described later) at the end of relaxing sessions to help clients come back to waking consciousness or in spa treatments that aim to energize and revitalize. Neurostimulant essential oils include bay laurel, black pepper, coriander, eucalyptus, grapefruit, lemon, peppermint, jasmine, rosemary, sweet fennel, tarragon, and thyme.

Dopamine Balancers

Dopamine balances are agents that increase or balance the levels of dopamine in the body. Dopamine relates to the brain’s reward system, where behaviors associated with biological advantages bring a sense of gratification. For example, it is released naturally during pleasurable activities like eating and sex.

Certain drugs like cocaine, nicotine, and amphetamines increase dopamine levels, which may be why they cause addictions. Dopamine plays a role in motor activity, mood, sensations of well-being, sleep patterns, allocation of attention, and learning. Dopamine disorders can cause a decline in cognitive functions like memory, concentration, and problem-solving. Low levels are related to attention deficit hyperactivity disorder (ADHD).

Numerous studies have shown that massage increases dopamine levels, indicating massage for depression, bulimia, anorexia, ADHD, and improved cognitive function. Increased dopamine also explains the enjoyment people experience from massage. In some cases, massage seems to balance dopamine and serotonin levels—lowering dopamine and raising serotonin. In the limited research conducted on essential oils, bergamot, clary sage, lavender, lemon, and melissa increase dopamine levels.²⁴ Linalool, a component of lavender, bay laurel, and basil, among others, was able to elevate suppressed dopamine levels and bring them into balance in rat studies.²⁵

Dopamine balancers are an excellent choice for use in massages when people report that they feel “off” and want to experience a greater sense of interconnected equilibrium.

Serotonin Stimulants

Serotonin stimulants are agents that increase or balance levels of serotonin in the body. Serotonin is a neurotransmitter found in the central nervous system related to mood, sleep, sexuality, appetite, and other body functions.

Low or abnormal serotonin levels are associated with depression, angry or aggressive behavior, anxiety disorders, and obsessive-compulsive disorders. It may also be a factor in migraine headaches and fibromyalgia. Research indicates that massage and aromatherapy massage increase or balance serotonin levels. These positive effects aid clients living with depression, past sexual abuse, eating disorders, pain syndromes, chronic fatigue, job stress, and pregnancy stress. Inhalations of Atlas cedarwood, bergamot, clary sage, lavender, lemon, Roman chamomile, rose, sandalwood, and sweet orange demonstrate serotonin-balancing effects in current research.²⁶

Euphorics

Euphorics are agents that promote positive feelings of expansion, connection, and consciousness. In general terms, euphorics work by increasing the activity of the prefrontal cortex. They also act directly on some types of serotonin receptors. Euphorics sedate the amygdala and the thalamus. We already know the amygdala is part of the limbic system and associated with fear responses and pleasure. The thalamus is a small structure within the brain located just above the brain stem that works to relay motor and sensory signals to the cerebral cortex. It regulates sleep, alertness, and wakefulness.

Euphorics typically contain small amounts of psychedelic substances—but don’t be confused. When used in standard concentrations, euphorics in aromatherapy are not remotely as strong as psychedelic mushrooms or peyote. For example, we use ground nutmeg for coffee and baking. Nutmeg contains a psychoactive chemical called myristicin, which has a chemical structure similar to mescaline, amphetamine, and ecstasy.²⁷

If you were to swallow a bottle of nutmeg essential oil, you would get very sick and could potentially die. However, when nutmeg essential oil is applied topically or inhaled using standard aromatherapy methods, it’s generally safe. Nutmeg creates a pronounced feeling of connection and a sense of expansion. Nutmeg is a profoundly connecting ingredient for your massage lubricants. It’s also a great essential oil to diffuse for meditation and yoga classes.

Euphorics typically have deep ties to ritual use in ancient cultures because of their psychoactive components. For example, the ritual use of frankincense in the ancient world was widespread. Its psychoactive effects were well known and documented by the Egyptians, Greeks, Romans, and pre-Islamic Arabs.²⁸ People believed frankincense smoke was purifying, and stood over the smoke to spiritually cleanse themselves. Frankincense was used in ceremonies to bring people into “one mind” and to help them lift their thoughts from earthly concerns to the glory of sun gods and goddesses.²⁹ In ancient Egypt, they burned frankincense at sunrise to welcome Ra—the sun god—into the sky each morning.³⁰

Modern scientists confirm that burning frankincense causes euphoria because two components in the resin (olivetol and verbenol) react when burned to form tetrahydrocannabinol (THC), the active ingredient in cannabis.³¹ THC is not present in frankincense essential oil. However, it is still considered euphoric because of the presence of incensole acetate, widely researched as an antianxiety and antidepressant agent.

Along with frankincense and nutmeg, several other essential oils contain gentle euphoric properties that give us a sense of ease and well-being. These essential oils include bergamot, blue lotus, cardamom, clary sage, clove bud, cypress, ginger, grapefruit, helichrysum, jasmine, neroli, and rosemary.

Synergies for Massage

You can bring essential oils and their beneficial psychological effects to your session room by using an aromatherapy massage lubricant and an aroma mist. I suggest using the neurostimulant synergy in an aroma mist to help the client return to alert consciousness after the session. Use the other formulations for your massage lubricants. Try these synergies to get started:

• Amygdala synergy: five drops lavender, one drop valerian, eight drops bergamot

• Antidepressant synergy: eight drops sweet orange, two drops clary sage, four drops frankincense

• Neurosedative synergy: nine drops Atlas cedarwood, seven drops bitter orange, two drops neroli, one drop sweet marjoram

• Neurostimulant synergy: four drops rosemary, nine drops grapefruit, one drop jasmine

• Dopamine synergy: eight drops lemon, four drops lavender, two drops clary sage

• Serotonin synergy: ten drops sandalwood, one drop rose, eight drops sweet orange

• Euphoric synergy: four drops cardamom, two drops nutmeg, eight drops bergamot, two drops cypress

• Brain balance synergy: eight drops bergamot, four drops frankincense, four drops lavender, two drops nutmeg

Massage Lubricant

To make a massage lubricant, combine 1 ounce of plain massage cream, lotion, or expeller-pressed vegetable oil with 12–24 drops of a synergy. Avoid creams and lotions with dyes, fragrance, mineral oil, or lanolin. If you opt to use vegetable oils as your carrier, choose organic expeller-pressed oils. For example, sunflower oil and avocado oil have a nice consistency.

Aroma Mist

To make an aroma mist, combine 12–24 drops of an essential oil synergy with 1 ounce of distilled water in a bottle with a fine-mist top. Then, add 1 tablespoon of grain alcohol (e.g., vodka) to give the formula a little added sparkle. You might also add 3–6 drops of a particular synergy to an electric diffuser running in your session room. If you want to make larger quantities, just double the drops and the carrier product. Spritz aroma mists in a high arch over the client when they are in the supine position. Don’t treat the client like a windshield and spray them directly with the mist. Mists used at the end of the session fill the room with aromas clients can enjoy as they dress for departure.

Final Thoughts

Use your aromatherapy synergies in massage exchanges with friends until you feel confident suggesting them to clients. Then, you’ll want to add an additional charge of between $10 and $15 to cover your aromatherapy expenses. When it comes to the essential oils you use in your practice, follow the “buyer beware” advice. While many suppliers offer purity reports on their essential oils, it takes a lot of expertise to read these analyses properly. In addition, some suppliers do the oil testing themselves, so it may be difficult to trust their results. Some aromatherapists have their oils independently tested, but this is costly (up to $200 per sample). The best option is to buy from well-respected aromatherapy-specific suppliers frequented by long-time aromatherapists. (My favorites are Florihana, Fragrant Earth, Original Swiss Aromatics, and Samara Botane.)

Adding aromatherapy to your practice creates new opportunities for you and your clients. Finding ways to incorporate it into your sessions for the well-being of your clients’ psychological health opens a whole new level of care to your hands-on work.

Notes

1. Lorena R. Lizarraga-Valderrama, “Effects of Essential Oils on Central Nervous System: Focus on Mental Health,” Phytotherapy Research 35, no. 2 (February 2020): 657–79, https://doi.org/10.1002/ptr.6854.

2. H. M. A. Cavanagh and J. M. Wilkinson, “Biological Activities of Lavender Essential Oil,” Phytotherapy Research 16, no. 4 (June 2002): 301–8, https://doi.org/10.1002/ptr.1103.

3. F. L. Angelucci et al., “Physiological Effects of Olfactory Stimuli Inhalation in Humans: An Overview,” International Journal of Cosmetic Science 36, no. 2 (April 2014): 117–23, https://doi.org/10.1111/ics.12096.

4. Babar Ali et al., “Essential Oils Used in Aromatherapy: A Systematic Review,” Asian Pacific Journal of Tropical Biomedicine 5, no. 8 (August 2015): 601–11, https://doi.org/10.1016/j.apjtb.2015.05.007.

5. Amir Vokshoor, “Olfactory System Anatomy,” Medscape, updated September 25, 2013, https://emedicine.medscape.com/article/835585-overview

6. Trygg Engen, The Perception of Odors (New York: Academic Press, 2012).

7. Walter F. Boron and Emile L. Boulpaep, Medical Physiology, 2nd ed. (Philadelphia: Saunders, 2012).

8. R. Gabriel Joseph, Limbic System: Hypothalamus, Amygdala, Hippocampus Septal Nuclei, Cingulate (Cambridge: Cosmology Science Publishers, 2017).

9. S. Torii et al., “Contingent Negative Variation (CNV) and the Psychological Effects of Odour,” in Perfumery, eds. S. Van Toller and G. H. Dodd (Netherlands: Springer, Dordrecht, 1988), 107–120, https://doi.org/10.1007/978-94-009-1215-1_6.

10. Lucian Hritcu, Oana Cioanca, and Monica Hancianu, “Effects of Lavender Oil Inhalation on Improving Scopolamine-Induced Spatial Memory Impairment in Laboratory Rats,” Phytomedicine 19, no. 6 (April 2012): 529–34, https://doi.org/10.1016/j.phymed.2012.02.002.

11. Mark Moss and Lorraine Oliver, “Plasma 1,8-Cineole Correlates with Cognitive Performance Following Exposure to Rosemary Essential Oil Aroma,” Therapeutic Advances in Psychopharmacology 2, no. 3 (June 2012): 103–13, https://doi.org/10.1177/2045125312436573.

12. Susanne Ambrosch et al., “Effects of 1,8-Cineole and (–)-Linalool on Functional Brain Activation in a Working Memory Task,” Flavour and Fragrance Journal 33, no. 3 (January 2018): 235–44, https://doi.org/10.1002/ffj.3436.

13. Eva Heuberger, “Effects of Essential Oils on Human Cognition,” in Handbook of Essential Oils: Science, Technology, and Application, 3rd ed., eds. K. Husnu Can Baser and Gerhard Buchbauer (Boca Raton: CRC Press, 2020), 345–71.

14. Eva Heuberger and Josef Ilmberger, “The Influence of Essential Oils on Human Vigilance,” Natural Product Communication 5, no. 9 (September 2010), https://doi.org/10.1177/1934578X1000500919; Elizabeth Varney and Jane Buckle, “Effect of Inhaled Essential Oils on Mental Exhaustion and Moderate Burnout: A Small Pilot Study,” Journal of Alternative and Complementary Medicine 19, no. 1 (January 2013): 69–79, https://doi.org/10.1089/acm.2012.0089.

15. Elisa Calvi et al., “The Scent of Emotions: A Systematic Review of Human Intra- and Interspecific Chemical Communication of Emotions,” Brain and Behavior 10, no. 5 (May 2020): 1–19, https://doi.org/10.1002/brb3.1585.

16. Tapanee Hongratanaworakit, “Aroma-Therapeutic Effects of Massage Blended Essential Oils on Humans,” Natural Product Communications 6, no. 8 (August 2011): 1199–204, https://pubmed.ncbi.nlm.nih.gov/21922934/.

17. Angela S. Lillehei and Linda L. Halcon, “A Systematic Review of the Effects of Inhaled Essential Oils on Sleep,” Journal of Alternative and Complementary Medicine 20, no. 6 (June 2014): 441–51, https://doi.org/10.1089/acm.2013.0311.

18. Angela S. Lillehei and Linda L. Halcon, “A Systematic Review of the Effects of Inhaled Essential Oils on Sleep.”

19. Scott A. Johnson, Damian Rodriguez, and Kathryn Allred, “A Systematic Review of Essential Oils and the Endocannabinoid System: A Connection Worthy of Further Exploration,” Evidence-Based Complementary and Alternative Medicine 2020, no. 25 (May 2020): 1–13, https://doi.org/10.1155/2020/8035301.

20. Damião P. de Sousa et al., “Essential Oils and Their Constituents: An Alternative Source for Novel Antidepressants,” Molecules 22, no. 8 (August 2017): 1290, https://doi.org/10.3390/molecules22081290.

21. R. Awad et al, “Effects of Traditionally Used Anxiolytic Botanicals on Enzymes of the Gamma-Aminobutyric Acid (GABA) System,” Canadian Journal of Physiology and Pharmacology 85, no. 9 (2007): 933–42, https://doi.org/10.1139/Y07-083.

22. Vittoria Borgonetti et al., “Novel Therapeutic Approach for the Management of Mood Disorders: In Vivo and In Vitro Effect of a Combination of L-Theanine, Melissa officinalis L. and Magnolia officinalis Rehder & E. H. Wilson,” Nutrients 12, no. 6 (June 2020): 1803, https://doi.org/10.3390/nu12061803.

23. Elizabeth Varney and Jane Buckle, “Effect of Inhaled Essential Oils on Mental Exhaustion and Moderate Burnout: A Small Pilot Study”; Eva Heuberger and Josef Ilmberger, “The Influence of Essential Oils on Human Vigilance”; Mark Moss and Lorraine Oliver, “Plasma 1,8-Cineole Correlates with Cognitive Performance Following Exposure to Rosemary Essential Oil Aroma.”

24. Mirte Brom et al., “The Role of Conditioning, Learning and Dopamine in Sexual Behavior: A Narrative Review of Animal and Human Studies,” Neuroscience and Biobehavioral Reviews 38 (January 2014): 38–59, https://doi.org/10.1016/j.neubiorev.2013.10.014.

25. Alessandra Tiziana Peana and Mario D. L. Moretti, “Linalool in Essential Plant Oils: Pharmacological Effects,” in Botanical Medicine in Clinical Practice, eds. V. R. Freedy and R. R. Watson (Oxfordshire: CAB International, 2008), 716–24, https://doi.org/10.1079/9781845934132.0000.

26. Babar Ali et al., “Essential Oils Used in Aromatherapy: A Systematic Review”; Tapanee Hongratanaworakit, “Aroma-Therapeutic Effects of Massage Blended Essential Oils on Humans”; Paul Michael Ziemba et al., “Activation and Modulation of Recombinantly Expressed Serotonin Receptor Type 3A by Terpenes and Pungent Substances,” Biochemical and Biophysical Research Communications 467, no. 4 (October 2015), 1090–96, https://doi.org/10.1016/j.bbrc.2015.09.074.

27. James A. Bourgeois, Usha Parthasarathi, and Ana Hategan, “Taking the Spice Route: Psychoactive Properties of Culinary Spices,” Current Psychiatry 13, no. 4 (April 2014): 21–32.

28. Isaac Asimov, The Near East: 10,000 Years of History (Boston: Houghton Mifflin Harcourt, 1968).

29. Susan J. Bandes, “Frankincense and Myrrh: Objects from the Red Sea Trade Routes during the Roman Empire,” Kresge Art Museum, Michigan State University, September 19–October 30, 1988.

30. Kelly Campbell-Hinshaw, Ancient Egypt (San Francisco, Chronicle Books, 2007).

31. Akhtar J. Khan, “Medicinal Properties of Frankincense,” International Journal of Nutrition, Pharmacology, Neurological Diseases 2, no. 2 (May–August 2012): 79, https://doi.org/10.4103/2231-0738.95925.