Last updated: March 2026
What Is Aromatherapy?
Aromatherapy is the therapeutic use of essential oils - concentrated volatile aromatic compounds extracted from plants - for physical, emotional, and spiritual well-being. The discipline sits at the intersection of herbal medicine, sensory psychology, and holistic healing, drawing on both ancient aromatic traditions and an expanding body of clinical research.
The word "aromatherapy" was coined by French chemist Rene-Maurice Gattefosse in his 1937 book Aromatheerapie, but the practice it names is far older than the word. Human beings have burned aromatic plant materials in ritual and healing contexts for at least 60,000 years - archaeological evidence from Shanidar Cave in Iraq documents medicinal plant use by Neanderthals, and the aromatic properties of many healing plants are precisely what made them culturally and therapeutically significant.
Essential oils are not oils in the usual sense - they are not fatty acids but volatile terpene and phenolic compounds that evaporate easily at room temperature (which is why you can smell a sliced lemon from across the room). The concentration involved is significant: it takes approximately 50 roses to produce a single drop of rose essential oil, 100kg of lavender flowers to produce 1kg of lavender essential oil. This concentration is both what makes essential oils therapeutically potent and why they must be used with appropriate respect and dilution.
History: From Ancient Egypt to Modern Clinics
The use of aromatic plants in healing and spiritual practice is documented across virtually every ancient civilisation. The Egyptian Ebers Papyrus (c. 1550 BCE), one of the oldest preserved medical documents, describes the use of myrrh, frankincense, cinnamon, and other aromatic substances in medicine and religious ritual. The Egyptians used a complex aromatic blend called kyphi - containing 16 ingredients including honey, wine, raisins, frankincense, myrrh, and various aromatic resins - in temple ritual, as an antidepressant, and as a sleep aid. Egyptian aromatic knowledge was fundamental to their sophisticated embalming practice, which could preserve bodies for millennia.
In ancient India, Ayurvedic medicine developed detailed protocols for aromatic plant use within the framework of the three doshas (vata, pitta, kapha). Sesame oil infused with herbs (tailas) and aromatic smoking treatments (dhumapana) were systematic therapeutic applications. The Sanskrit texts contain detailed pharmacological descriptions of hundreds of aromatic plants.
Greek medicine absorbed Egyptian and Persian aromatic knowledge through Alexander's conquests. Theophrastus's Inquiry into Plants (c. 300 BCE) described aromatic plant properties systematically, and Dioscorides's De Materia Medica (c. 50 CE) - the reference pharmacopoeia used throughout the Mediterranean world for over 1,500 years - described aromatic plants extensively.
The major technical advance was distillation. While rudimentary distillation had been practiced earlier, the Arab scholar Ibn Sina (Avicenna, 980-1037 CE) is credited with developing or significantly refining the coiled cooling pipe (alembic) for steam distillation - the technique that made it possible to efficiently extract and concentrate the volatile aromatic compounds of plants in the form we now call essential oils. Ibn Sina's Canon of Medicine (Al-Qanun fi al-Tibb) described the medicinal uses of numerous aromatic plants and their distilled preparations.
European herbal medicine from the medieval period onward used distilled aromatic waters (hydrosols) and, increasingly, concentrated essential oils. French chemist Rene-Maurice Gattefosse's 1937 book established the term "aromatherapy" and a clinical framework; French physician Jean Valnet further developed clinical practice, treating World War II soldiers' wounds with essential oils when antibiotics were unavailable. British nurse Marguerite Maury developed the massage application of aromatherapy. The modern aromatherapy movement grew from these French clinical roots through the 1970s and 1980s.
How Essential Oils Work: Mechanisms
The Olfactory Pathway
When aromatic molecules are inhaled, they pass through the nasal cavity and bind to olfactory receptor proteins on the cilia of olfactory receptor neurons in the olfactory epithelium (a small area of tissue at the top of the nasal cavity). These neurons send signals directly to the olfactory bulb - a brain structure that then connects directly to the limbic system, including the amygdala (emotional processing and threat detection), the hippocampus (memory formation and retrieval), and the hypothalamus (which regulates hormonal responses, sleep, hunger, and the autonomic nervous system).
This olfactory-limbic pathway is uniquely direct compared to other sensory modalities. Visual and auditory information passes through the thalamus before reaching emotional processing centres. Olfactory information goes straight to the limbic system first, then to the cortex. This is why scent has such immediate, visceral effects on mood and memory - and why aromatherapy can produce physiological changes (heart rate, cortisol levels, brain wave patterns) without any conscious interpretation of the smell.
Skin Absorption
Essential oils are lipophilic (fat-soluble) and small enough in molecular size to penetrate the skin through the stratum corneum (the outer skin layer). When applied topically in carrier oils, aromatic compounds enter the bloodstream and can exert systemic effects. The rate and extent of skin absorption varies with the compound, the carrier, the application site, skin condition, and temperature. Tea tree oil applied topically to wounds has documented antimicrobial effects that cannot be explained by surface contact alone - indicating systemic absorption.
Direct Pharmacological Action
Many essential oil constituents have direct pharmacological activity: linalool (a major component of lavender) has documented GABAergic effects (similar to anti-anxiety medications), explaining lavender's well-studied anxiolytic effects. 1,8-cineole (the main constituent of eucalyptus) inhibits inflammatory mediators and acts as a bronchodilator. Limonene (citrus oils) has documented anti-inflammatory and potentially anti-tumour effects in preclinical research. Eugenol (clove) has well-established local anaesthetic and antimicrobial properties used in dentistry.
Extraction Methods
Steam distillation: The most common method. Steam is passed through plant material, carrying volatile aromatic compounds upward; the steam then condenses back into water and oil, which are separated. The water phase is the hydrosol (floral water); the oil phase is the essential oil. Best for most herbs and flowers. Heat-sensitive compounds may be altered.
Cold pressing (expression): Used exclusively for citrus peel (lemon, orange, grapefruit, bergamot). The peel is mechanically pressed or centrifuged to release the essential oil directly. No heat is involved, so the citrus character is more vibrant and authentic. Cold-pressed citrus oils are more phototoxic (causing skin reactions in sunlight) than distilled versions because they retain more of the furanocoumarin compounds.
CO2 extraction (supercritical fluid extraction): Carbon dioxide at supercritical pressure and temperature acts as a solvent, extracting aromatic compounds selectively without the heat damage of distillation. Produces the most chemically complete and therapeutically rich extracts but is expensive and requires specialised equipment. CO2-extracted frankincense, turmeric, and sea buckthorn are considered significantly superior to steam-distilled equivalents.
Enfleurage: An ancient cold process using fat to absorb aromatic compounds from delicate flowers (jasmine, tuberose) that cannot withstand distillation heat. The fat is then washed with alcohol to remove the aromatic compounds. Rarely used commercially due to labour intensity, but produces extraordinarily fine extracts.
Research Evidence
The research landscape for aromatherapy is growing but uneven. The most well-supported applications include:
Anxiety: Multiple randomised controlled trials support lavender for anxiety reduction. A 2014 systematic review by Perry and colleagues found evidence from 15 trials supporting lavender's anxiolytic effects. A licensed oral lavender preparation (Silexan) has been studied in clinical trials for anxiety disorders and found effective. Bergamot and neroli also have supporting evidence.
Sleep: Lavender inhalation has been studied in multiple populations (older adults, postnatal women, ICU patients, students during exam periods) with generally positive effects on sleep quality. A 2015 meta-analysis found statistically significant positive effects across studies.
Tension headache: Peppermint oil applied topically to the forehead (in 10% ethanol solution) has been compared to acetaminophen in controlled trials (Göbel et al., 1996) with equivalent efficacy for tension headache, superior tolerability, and faster onset.
Postoperative nausea: Ginger and peppermint aromatherapy have evidence from clinical trials for reducing postoperative nausea and vomiting, though effect sizes are modest.
Antimicrobial activity: Tea tree, oregano, thyme, and clove have well-documented antimicrobial properties in laboratory settings. Clinical evidence for their application in treating infections is more limited but growing.
25 Essential Oils: Properties and Applications
| Oil | Key Constituents | Primary Applications | Cautions |
|---|---|---|---|
| Lavender | Linalool, linalyl acetate | Anxiety, sleep, minor burns, skin healing | Generally safe; avoid near infants |
| Peppermint | Menthol, menthone | Headache, nausea, alertness, congestion | Avoid near infants; CNS-active |
| Tea tree | Terpinen-4-ol, gamma-terpinene | Antimicrobial, skin infections, wound care | Toxic if ingested; oxidised oil more irritating |
| Frankincense | Alpha-pinene, incensole acetate | Anxiety, immune support, spiritual practice | Generally safe |
| Eucalyptus | 1,8-cineole | Respiratory, congestion, antimicrobial | Toxic to children under 2 if ingested |
| Rosemary | 1,8-cineole, camphor | Memory, alertness, hair growth, pain | Avoid in pregnancy, epilepsy, hypertension |
| Lemon | Limonene (cold-pressed) | Mood-lifting, antimicrobial, cleaning | Phototoxic (cold-pressed); use distilled for skin |
| Chamomile (German) | Alpha-bisabolol, chamazulene | Anti-inflammatory, skin, sleep, anxiety | Potential allergy in those sensitive to Asteraceae |
| Ylang ylang | Benzyl acetate, linalool | Mood-lifting, aphrodisiac, blood pressure | Headache at high doses; use sparingly |
| Sandalwood | Alpha-santalol, beta-santalol | Meditation, anxiety, skin, spiritual | Indian sandalwood (Santalum album) is endangered; use Australian (S. spicatum) or New Caledonian alternatives |
| Bergamot | Linalyl acetate, limonene | Anxiety, depression, mood-lifting | Phototoxic unless bergapten-free |
| Rose (otto) | Geraniol, citronellol, nerol | Emotional healing, hormone balance, skin | Very expensive; verify purity |
| Clary sage | Linalyl acetate, sclareol | Hormone balance, PMS, menstrual pain, anxiety | Avoid in pregnancy; avoid with alcohol |
| Geranium | Citronellol, geraniol | Skin balance, hormone support, mood | Generally safe; possible sensitisation |
| Vetiver | Khusimol, vetivene | Grounding, ADHD support, anxiety, sleep | Generally safe |
| Ginger | Zingiberene, beta-bisabolene | Nausea, digestion, pain, warming | Possible skin irritation; use diluted |
| Clove | Eugenol | Dental pain, antimicrobial, antioxidant | Strong irritant; use very diluted |
| Cedarwood (Atlas) | Alpha-cedrene, cedrol | Grounding, ADHD, sleep, hair loss | Avoid in pregnancy |
| Jasmine absolute | Benzyl acetate, indole | Emotional uplifting, aphrodisiac, confidence | Absolute (not essential oil); dilute well |
| Myrrh | Curzerene, furanoeudesma | Anti-inflammatory, wound healing, meditation | Avoid in pregnancy |
| Oregano | Carvacrol, thymol | Antimicrobial, antifungal, immune support | Strong irritant; never use undiluted; not long-term |
| Neroli | Linalool, linalyl acetate, nerol | Anxiety, sleep, skin regeneration | Generally safe; expensive |
| Helichrysum | Neryl acetate, italidiones | Bruising, wound healing, anti-inflammatory | Generally safe; verify Helichrysum italicum species |
| Patchouli | Patchouli alcohol, alpha-bulnesene | Grounding, skin care, anti-inflammatory | Generally safe; strong scent - use sparingly |
| Lemongrass | Geranial, neral (citral) | Antimicrobial, mood-lifting, insect repellent | Potential skin sensitiser; use diluted |
Safety and Dilution Guidelines
Essential oils are among the most concentrated plant preparations available, and they require appropriate respect and knowledge for safe use. Key safety principles:
- Always dilute for skin application: Standard adult dilution is 2-3% (approximately 12-18 drops per 30ml carrier oil). Face: 1% or less. Children 6-12: 1%. Children under 6: specialist guidance only.
- Patch test: Apply a small amount of diluted oil to the inside of the wrist, cover for 24 hours, observe for redness, itching, or swelling before using more broadly.
- Photosensitising oils: Cold-pressed citrus oils (lemon, lime, bergamot, grapefruit) contain furanocoumarins that react with UV light to cause burns and pigmentation. Avoid sunlight exposure for 12-18 hours after applying to skin, or use steam-distilled versions or bergapten-free bergamot.
- Contraindications: Several oils should be avoided in pregnancy, with epilepsy, with certain medications, or in young children. When in doubt, consult a qualified aromatherapist or naturopathic practitioner.
- Pets: Many essential oils are toxic to cats (phenolic oils including tea tree, clove, oregano, thyme) and dogs. Never diffuse heavily in enclosed spaces with pets present.
- Storage: Keep in dark glass bottles away from heat and light. Most oils maintain quality for 2-4 years; citrus oils 1-2 years; resins and woods many years or decades if properly stored.
Application Methods
Diffusion: Ultrasonic diffusers disperse essential oil microdroplets in water vapour. Use 3-6 drops per 100ml water. Run for 30-60 minutes, ventilate the room, then rest. Avoid continuous all-day diffusion. Heat diffusers (candle, plug-in) degrade some beneficial compounds; ultrasonic is preferred.
Topical application: Dilute in carrier oil and apply to the targeted area (temples for headache, chest for respiratory, abdomen for digestive). Reflexology-informed practitioners apply to specific foot zones corresponding to the target area.
Steam inhalation: Add 2-3 drops to a bowl of hot water, cover head with a towel, and inhale for 5-10 minutes. Effective for respiratory conditions. Keep eyes closed; hot steam can damage eyes.
Bath: Disperse 4-6 drops in a teaspoon of carrier oil or whole milk (not directly in water - essential oils do not disperse in water and can cause skin irritation). Add to bath, soak for 15-20 minutes.
Compress: Add 2-4 drops to warm or cold water, soak a cloth, and apply to the affected area. Warm compress for muscle pain and menstrual cramps; cold compress for headache and inflammation.
Blending Principles
Aromatic blending follows musical principles - notes that create harmony when combined. Traditional aromatherapy blending uses the perfumery concept of top, middle, and base notes:
Top notes (first impression, most volatile, 15-30 minute duration): citrus oils, peppermint, eucalyptus, tea tree, basil. These are the first scents perceived and the first to evaporate.
Middle notes (the heart of the blend, 2-4 hour duration): lavender, rosemary, chamomile, geranium, clary sage, ylang ylang, rose, jasmine. The body of the blend.
Base notes (the anchor, longest duration): vetiver, patchouli, sandalwood, cedarwood, frankincense, myrrh, benzoin. These slow the evaporation of the entire blend and provide its lasting depth.
A balanced blend typically uses approximately 30% top notes, 50% middle notes, and 20% base notes. Start with total drops of 10-12 per 10ml carrier oil for a standard 2% dilution, adjust the ratio within that total.
Spiritual and Consciousness Applications
Aromatic plants have been integral to human spiritual practice since before recorded history. The direct limbic pathway of olfaction - its capacity to immediately shift emotional and physiological state - makes aromatherapy one of the most accessible tools for supporting altered states, meditation depth, and ceremonial space.
Frankincense (Boswellia sacra) occupies a unique position as the most universally significant spiritual aromatic in the Western and Middle Eastern traditions. Used in ancient Egyptian temple ritual, central to the Hebrew Temple service (the Ketoret incense blend contained frankincense), referenced in Christian Scripture (among the three Magi's gifts), and used in Catholic and Orthodox incense to this day, frankincense has an unbroken lineage of spiritual use spanning more than 5,000 years. Recent research by Moussaieff and colleagues (2008) at Hebrew University found that incensole acetate (a compound unique to frankincense) activates TRPV3 ion channels in the brain, producing "warm feelings and a sense of well-being" - a molecular basis for the spiritual elevation traditionally attributed to frankincense smoke.
Key Takeaways
- Aromatherapy works primarily through the olfactory-limbic pathway - aromatic molecules travel directly to the brain's emotional centre (the limbic system) without passing through cortical reasoning circuits, explaining the immediate mood and physiological effects of scent.
- The best research-supported aromatherapy applications include lavender for anxiety and sleep, peppermint for tension headache, tea tree for antimicrobial use, and ginger for nausea.
- Essential oils must be diluted for skin application (standard adult: 2-3% in carrier oil); photosensitising citrus oils require avoiding sunlight; several oils are contraindicated in pregnancy, with epilepsy, or near young children and pets.
- The most significant spiritual aromatic is frankincense, with unbroken use across Egyptian, Hebrew, Christian, and Islamic traditions spanning over 5,000 years; recent research has identified incensole acetate as a biologically active compound producing warm feelings and well-being.
- Aromatherapy blending follows perfumery note principles (top/middle/base) creating harmonious, long-lasting aromatic compositions; chakra-aligned blending matches oil properties to the energetic qualities of each energy centre.
Frequently Asked Questions
What is aromatherapy and how does it work?
Aromatherapy is the therapeutic use of essential oils - concentrated volatile aromatic compounds extracted from plants through distillation, cold pressing, or solvent extraction - for physical, emotional, and spiritual well-being. The primary mechanism is olfactory: aromatic molecules inhaled through the nose bind to olfactory receptor proteins in the nasal epithelium, triggering nerve signals transmitted directly to the limbic system (the brain's emotional and memory centre) via the olfactory bulb. This direct pathway to the limbic system - bypassing the cortical reasoning circuits - explains why scent has such immediate effects on mood, emotional state, and memory. Secondary mechanisms include absorption through the skin when applied topically (diluted in carrier oils) and inhalation of steam-borne molecules during steam inhalation or bath use.
What does the research say about aromatherapy effectiveness?
The research on aromatherapy varies considerably by condition and oil. The best-established evidence supports: lavender (Lavandula angustifolia) for anxiety reduction - a 2014 Cochrane review found meaningful evidence for anxiety reduction in clinical settings; peppermint (Mentha piperita) for tension headache relief - controlled trials show efficacy comparable to acetaminophen for tension headaches when applied topically; tea tree (Melaleuca alternifolia) for antimicrobial activity - multiple in vitro and some in vivo studies confirm broad-spectrum antimicrobial effects; and chamomile for sleep quality improvements. More limited but suggestive evidence exists for many other applications. The research base is growing but uneven, and practitioners should distinguish between well-supported and speculative claims.
What are the most important essential oils to start with?
For a foundational aromatherapy collection, five oils provide the widest range of well-studied applications: Lavender (Lavandula angustifolia) - versatile, gentle, extensively studied for anxiety, sleep, minor burns, and skin care; Peppermint (Mentha piperita) - energising, cooling, studied for headache, nausea, mental alertness, and respiratory support; Tea tree (Melaleuca alternifolia) - antimicrobial, studied for skin infections, minor wounds, and oral health; Eucalyptus (Eucalyptus globulus or radiata) - respiratory support, studied for congestion and cough; and Frankincense (Boswellia sacra or carterii) - grounding, studied for anxiety, immune support, and the most spiritually significant oil in Western and Middle Eastern traditions.
Is aromatherapy safe during pregnancy?
Aromatherapy safety during pregnancy requires caution. Several essential oils are contraindicated throughout pregnancy because of their potential to stimulate uterine contractions or cause other adverse effects: these include clary sage, rosemary, juniper, thyme, basil, fennel, and several others. Some oils considered generally safe during the second and third trimesters (lavender, ginger, chamomile) may still require reduced concentrations. Aromatherapy use during the first trimester is generally avoided due to the sensitivity of early fetal development. Anyone pregnant or trying to conceive should consult with a qualified midwife, naturopathic doctor, or certified aromatherapist before using essential oils. This is a situation where professional guidance is not optional.
What is the difference between essential oils and fragrance oils?
Essential oils are natural volatile aromatic compounds extracted directly from plant material through steam distillation, cold-pressing (for citrus oils), or CO2 extraction. They contain the complex chemical constituents of the plant - hundreds of individual compounds in precise ratios characteristic of the plant species and variety, growing conditions, and extraction method. Fragrance oils are synthetic aromatic compounds designed to smell like specific things (roses, vanilla, ocean breeze) without containing any actual plant material. They are manufactured from petrochemicals and other synthetic precursors. Fragrance oils are safe for many purposes but have none of the bioactive properties of essential oils and should not be used in therapeutic aromatherapy applications. High-quality essential oils are significantly more expensive than fragrance oils because they represent concentrated natural plant material.
How are essential oils best applied safely?
Essential oils are highly concentrated and most require dilution before skin application. The standard dilution guideline for adults is 2-3% essential oil in a carrier oil (typically 12-18 drops per 30ml of carrier oil). Common carrier oils include jojoba, fractionated coconut oil, sweet almond oil, rosehip seed oil, and argan oil. The face and sensitive areas require 1% dilution or less. Essential oils should never be applied undiluted to the skin except in specific contexts (lavender on minor burns, tea tree on spots) with appropriate caution. They should not be used near eyes, in ears, or ingested without specific professional guidance. Diffusion is generally the safest route - add 3-6 drops to a water-based ultrasonic diffuser and diffuse in a ventilated space for 30-60 minutes at a time.
What is the history of aromatherapy?
Aromatic plant use for healing, spiritual practice, and wellbeing dates back at least 3,500 years. Ancient Egyptian papyri describe the use of aromatic resins (frankincense, myrrh, kyphi - a complex blend of 16 ingredients) in temple ritual, medicine, and embalming. Greek physicians including Hippocrates and Galen used aromatic herbs in medical practice. Arab scholar Ibn Sina (Avicenna, c. 980-1037 CE) is credited with developing or refining steam distillation for essential oil extraction - the technique still used today. The modern term 'aromatherapy' (aromatheerapie) was coined by French chemist Rene-Maurice Gattefosse in 1937 after he applied lavender oil to a laboratory burn and noted its rapid healing. French physician Jean Valnet subsequently developed clinical aromatherapy practice, and the field has grown substantially since the 1970s.
What essential oils are used in spiritual and consciousness practice?
Several essential oils have deep traditions of use in spiritual and consciousness contexts. Frankincense (Boswellia species) has been used in religious ritual across Egyptian, Jewish, Christian, and Islamic traditions for millennia - recent research suggests it may contain incensole acetate, a compound that activates ion channels in the brain associated with warm and transcendent feelings. Sandalwood (Santalum album) is fundamental to Hindu and Buddhist temple practice, used for meditation and devotional focus. Myrrh (Commiphora species) appears in Egyptian, Hebraic, and Christian sacred contexts as a purification and anointing agent. Palo santo (Bursera graveolens) is used in South American shamanic traditions for clearing and protection. Blue lotus (Nymphaea caerulea) was used in ancient Egyptian ceremonial contexts and has mild consciousness-influencing properties studied in recent research.
How does aromatherapy connect to chakra work?
Aromatherapy can be systematically applied to chakra work by matching essential oil properties and traditional associations with the energetic qualities of each chakra. Root chakra (muladhara): vetiver, patchouli, cedarwood - grounding, earthy, stabilising. Sacral chakra (svadhisthana): ylang ylang, orange, clary sage - sensual, creative, fluid. Solar plexus (manipura): ginger, lemon, rosemary - warming, activating, clarifying. Heart chakra (anahata): rose, jasmine, geranium - opening, loving, balanced. Throat chakra (vishuddha): blue chamomile, eucalyptus, clary sage - clarifying, expressive, cooling. Third eye (ajna): frankincense, clary sage, lavender - deepening, perceptive, calming. Crown chakra (sahasrara): frankincense, sandalwood, neroli - connecting, transcendent, purifying.
What is CO2 extraction and why does it produce superior essential oils?
CO2 (supercritical carbon dioxide) extraction uses carbon dioxide at elevated pressure to act as a solvent for aromatic compounds. At supercritical conditions (above 31.1 degrees Celsius and 73.8 bar pressure), CO2 has properties of both liquid and gas, allowing it to penetrate plant material and dissolve aromatic compounds with exceptional selectivity. When pressure is released, the CO2 evaporates cleanly, leaving behind the extracted compounds without solvent residue. CO2 extraction produces extracts with a more complete chemical profile than steam distillation because it captures heat-sensitive compounds that are altered or destroyed by the high temperatures of conventional distillation. CO2-extracted frankincense, turmeric, rosemary, and chamomile are considered superior to steam-distilled equivalents in terms of chemical completeness and therapeutic depth, though they are also more expensive.
Sources
- Perry, N., & Perry, E. (2006). Aromatherapy in the management of psychiatric disorders. CNS Drugs, 20(4), 257-280.
- Göbel, H., Schmidt, G., & Soyka, D. (1994). Effect of peppermint and eucalyptus oil preparations on neurophysiological and experimental algesimetric headache parameters. Cephalalgia, 14(3), 228-234.
- Moussaieff, A., Rimmerman, N., Bregman, T., Straiker, A., Felder, C. C., Shoham, S., ... & Mechoulam, R. (2008). Incensole acetate, an incense component, elicits psychoactivity by activating TRPV3 channels in the brain. FASEB Journal, 22(8), 3024-3034.
- Buckle, J. (2015). Clinical Aromatherapy: Essential Oils in Healthcare (3rd ed.). Churchill Livingstone Elsevier.
- Tisserand, R., & Young, R. (2013). Essential Oil Safety (2nd ed.). Churchill Livingstone Elsevier.
- Cavanagh, H. M., & Wilkinson, J. M. (2002). Biological activities of lavender essential oil. Phytotherapy Research, 16(4), 301-308.