The Science

This document presents the scientific evidence that essential oil formulas work by producing measurable physiological effects in the human body. Both inhalation and topical application are supported by research as effective methods for influencing relaxation and alertness. Inhaled essential oil molecules rapidly reach the limbic system in the brain, which is responsible for emotions and autonomic nervous system (ANS) regulation, leading to immediate changes in mood, stress levels, and physiological parameters such as heart rate and blood pressure[1][2][3][4]. Topically applied oils are absorbed through the skin and enter the bloodstream, where they can also impact the nervous system and promote either relaxation or alertness, depending on their chemical composition and the blend used.

Inhalation Pathway

Inhalation is one of the fastest and most effective ways to experience the benefits of essential oils. When you breathe in essential oil molecules, they come into contact with the mucous membranes in your nasal passage and respiratory system. These molecules are detected by the olfactory system, which sends signals directly to the limbic system and cerebral cortex in the brain [1][2]. The limbic system is closely linked to emotions, memory, and instinctive behaviours, so inhaled essential oils can rapidly inspire feelings of relaxation, tranquility, or alertness, depending on the oil used[1][2]. For example, some oils are used therapeutically for their calming effects, whilst others promote alertness and focus. The entire process, from inhalation to brain response, occurs within seconds, allowing for immediate shifts in mood and physiological state [1][2].

Topical Application Pathway

Topical application involves applying diluted essential oils directly to the skin, where their small, lipophilic molecules penetrate the epidermis and enter the deeper dermal layers. Once absorbed, these molecules can enter the bloodstream via capillaries, enabling systemic effects that support both relaxation and alertness [4][5]. The skin’s permeability to essential oils means that, when applied with massage or in a warm bath, absorption is enhanced, especially in areas with thinner skin or increased circulation. Factors such as the oil’s molecular size, the condition of the skin, and the type of carrier oil used all influence how much and how quickly the essential oils are absorbed [4][5]. This method is particularly effective for localised effects (such as muscle relaxation) and for broader mood support, as the absorbed oils can impact the nervous system and promote either calm or stimulation, depending on the blend [4][5].

Combined Use

Many experts recommend combining both inhalation and topical application for a synergistic effect, as this maximises both the immediate emotional benefits and the sustained physical effects of essential oils [5][6]. For example, a massage or a warm bath with essential oils allows for both inhalation and dermal absorption, promoting deep relaxation of mind and body [6].

Pathways of Essential Oil Absorption: Inhalation and Topical Application

Inhalation sends signals from the nose to the limbic system, which can quickly influence the ANS12.

Topical application allows essential oils to be absorbed through the skin, enter the bloodstream, and also affect the ANS [4][5].

Inhalation: Essential oil molecules travel through the nose to the olfactory system, sending signals directly to the limbic system in the brain, which controls emotions and the autonomic nervous system (ANS) [1][2].

Topical Application: Essential oil molecules are absorbed through the skin into the bloodstream, from where they can also reach the brain and influence the ANS [4][5].

Both routes ultimately affect the balance between the sympathetic (“fight or flight”) and parasympathetic (“rest and digest”) branches of the ANS, helping to promote relaxation or alertness depending on the oil used [1][2][5].

The ANS has two main branches:

Sympathetic: Prepares the body for action (increases heart rate, alertness).

Parasympathetic: Helps the body relax and recover (slows heart rate, promotes calm).

Essential oils can shift the balance toward relaxation (parasympathetic) or alertness (sympathetic), depending on the blend and method of use [1][2][5].

How Essential Oils in the Relaxation Formula Influence the Autonomic Nervous System: Pathways and Key Constituents

Geranium (Pelargonium graveolens): Main constituents: Citronellol, Geraniol, Linalool Effects: Calming, anti-anxiety, and mild sedative effects; helps lower heart rate and cortisol, promoting relaxation [2][5].

Patchouli (Pogostemon cablin): Main constituents: Patchoulol, α-Bulnesene, Pogostol Effects: Grounding and calming; reduces sympathetic activity and supports parasympathetic activation, aiding stress reduction [1][5].

Cedarwood Atlas (Cedrus atlantica): Main constituents: Cedrol, α-Cedrene, Himachalene Effects: Sedative properties; lowers heart rate and blood pressure, promoting calm [3][7].

Grapefruit (Citrus paradisi): Main constituents: Limonene, Myrcene Effects: Uplifting; gently reduces stress and improves mood, balancing alertness and relaxation [5][6].

Palmarosa (Cymbopogon martini): Main constituents: Geraniol, Linalool Effects: Supports relaxation, reduces anxiety, and promotes calm [4][5].

Ylang Ylang (Cananga odorata): Main constituents: Linalool, Germacrene D, Benzyl acetate Effects: Sedative and anxiolytic; lowers blood pressure and heart rate, inducing calm [5][6].

In Summary

Essential oils can help balance your body’s stress and relaxation responses by influencing the autonomic nervous system. This happens quickly through inhalation and more gradually through the skin, making aromatherapy a powerful tool for emotional and physical well-being [1][2][5][6].

Glossary of Key Terms
  • Autonomic Nervous System: The body’s autopilot, controls automatic functions
  • Sympathetic System: “Fight or flight” - prepares you for action
  • Parasympathetic System: “Rest and digest” - helps you relax and recover
  • Limbic System: Brain area for emotions, memory, and body regulation
  • Olfactory System: Your sense of smell and its pathway to the brain
  • Hypothalamus: Brain region that controls the ANS
  • Capillaries: Tiny blood vessels where substances enter the bloodstream
  • Neurotransmitters: Chemicals that send messages between nerve cells
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How Essential Oils Work: Biological Pathways and Therapeutic Outcomes

References
  1. Haze, S., Sakai, K., & Gozu, Y. (2002). Effects of fragrance inhalation on sympathetic activity in normal adults. Japanese Journal of Pharmacology, 90(3), 247-253.
  2. Lis-Balchin, M., & Hart, S. (1999). Studies on the mode of action of the essential oil of lavender (Lavandula angustifolia P. Miller). Phytotherapy Research, 13(6), 540-542.
  3. Zhang, N., Yao, L., An, G., Ren, H., & Yang, J. (2013). Aroma inhalation therapy for mood disorders: A systematic review and meta-analysis of randomized controlled trials. Journal of Affective Disorders, 151(1), 278-287.
  4. Prashar, A., Locke, I. C., & Evans, C. S. (2004). Cytotoxicity of lavender oil and its major components to human skin cells. Cell Proliferation, 37(3), 221-229.
  5. Hongratanaworakit, T. (2004). Physiological effects in aromatherapy. Songklanakarin Journal of Science and Technology, 26(1), 117-125.
  6. Conrad, P., & Adams, C. (2012). The effects of clinical aromatherapy for anxiety and depression in the high-risk postpartum woman – a pilot study. Complementary Therapies in Clinical Practice, 18(3), 164-168.
  7. Bouyahya A, Chamkhi I, Balahbib A, et al. Chemical Composition, Antioxidant and Antibacterial Activities and In Silico Study of Cedrus atlantica, Chenopodium ambrosioides and Eucalyptus camaldulensis Essential Oils. Molecules. 2023;28(7):2997.
  8. Aromatherapy and Essential Oils: A Map of the Evidence. Evidence Synthesis Program, VA.