Aromatherapy (Therapy) Overview

In aromatherapy, chemical compounds in oils are absorbed in the body through skin application and/or inhalation. Oils in certain herbs contain chemical compounds that activate the limbic system.

Rosemary, lemon, bergamont, jasmine and clary sage have been shown to have stimulating properties which can alleviate depressive symptoms of fatigue, lack of concentration, despair, and grief. Rose, lavender, ylang-ylang, neroli and sandalwood have been shown to have sedating properties which can reduce depressive symptoms of restlessness and sleep disturbance. These essential oils stimulate the raphe nucleus, which produces serotonin. Parsnip, parsley, and nutmeg contain the chemical myristicin, which has been shown to act as monoamine oxidase inhibitor.¹

Perhaps the most conclusive evidence of the efficacy of aromatherapy is that it has been used in many ancient healing traditions for thousands of years.² A report discussing the antidepressant properties of essential oils by Perry and Perry notes that some studies have shown aromatherapy improves mood in healthy adults.³ Yet there are very few sound clinical trials on the effects of aromatherapy specifically on clinically depressed persons. However, aromatherapy is seen as a potentially effective treatment for a range of psychiatric disorders and given it has few adverse side effects, further methodologically sounds research is clearly warranted.

Aromatherapy is actually a form of herbal medicine. However, instead of using the entire herb, it employs the fragrant "essential oil" that is released when a fresh herb is compressed or subjected to chemical extraction. Essential oils are also often used as fragrances in cosmetics and bath products.

When employed medicinally, essential oils are often evaporated into the air through the use of a humidifier. The famous Vicks VapoRub® is a gel form of the essential oils of peppermint, eucalyptus, and camphor. Essential oils may also be applied directly to the skin or clothes so they will release their odor near the patient.

Oils in certain herbs contain chemical compounds that activate the limbic system. Essential oils may be inhaled, taken by mouth, or applied to the skin.

There is a major difficulty in studying aromatherapy by inhalation: how to conduct a double-blind, placebo-controlled trial. For the results of a study to be truly reliable, both participants and researchers must be kept in the dark regarding participants who received real treatment and who received placebo. (For more information on why this is so crucial, see Why Does This Database Depend on Double-blind Studies? .) Although it may be possible to keep researchers in the dark regarding which group is which, participants will certainly be aware of whether they smell something or not! This is a problem because it has been shown that when researchers create expectations about the effects of certain aromas, those effects may occur simply because of those expectations. ¹ Researchers have used various clever compromises in an effort to partially solve this problem. For example, some studies used a control group that received an aromatic substance believed to be ineffective, without informing the members of the control group that this alternate aromatic substance won’t work. Unfortunately, it’s just as hard to prove that an aromatic substance is ineffective as it is to prove that it’s effective! If the placebo in a study is just as effective as the tested treatment, the study will falsely indicate that the tested treatment is ineffective. Furthermore, many odors already have associations attached them, based on cultural patterns. Lavender oil, for example, conjures up for many people memories of their grandmother. It simply is not possible to remove such expectations.

In other studies, researchers tricked participants in the control group and told them that they might be receiving an active but odorless treatment, when in fact they were simply given an inactive treatment without much in it. Still other studies managed to find ethical ways of keeping their study participants in the dark regarding whether they were enrolled in a study at all, and then introduced the odors surreptitiously. Partially effective compromises such as these are necessary. Unfortunately, most published studies on aromatherapy fail even to achieve this level of rigor, falling far below minimal scientific standards of reliability. ² Thus, everything written below about true aromatherapy—that is, inhalation of an aroma—must be taken with a grain of salt.

These problems do not arise to the same extent in studies of essential oils taken by mouth or applied directly to the skin.

Inhalation of Essential Oils

Calming Effects

Preliminary controlled trials suggest that various forms of aromatherapy might be helpful for calming people with Alzheimer's disease and other forms of dementia . ³ For example, in one interestingly designed, but very small, study, a hospital ward was suffused with either lavender oil or water for two hours. ⁴ An investigator who was unaware of the study’s design and who wore a device to block inhalation of odors entered the ward and evaluated the behavior of the 15 residents, all of whom had dementia. The results indicated that use of lavender oil aromatherapy modestly decreased agitated behavior. A less rigorous study also reported benefit with lavender. ⁵ However, people with dementia tend to lose their sense of smell, making this approach seem somewhat limited in its usefulness. ⁶ Essential oil of lemon balm has also shown promise for this purpose; in a double-blind study of 71 people with severe dementia, use of a lotion containing essential oil of lemon balm reduced agitation compared to placebo lotion. ⁷ Here, absorption through the skin may have played a role.

Several relatively poorly designed studies hint that aromatherapy combined with massage may help to relieve anxiety in people without Alzheimer's disease. ⁸ Another study suggests that aromatherapy with geranium oil might modestly reduce anxiety levels (again in people without Alzheimer's). ⁹ However, in a trial of 66 women waiting to undergo abortions, 10 minutes of inhaling the essential oils of vetivert, bergamot, and geranium failed to reduce anxiety significantly more than placebo treatment. ¹⁰ In another study, rosemary oil failed to reduce tension during an anxiety provoking task, and might have actually increasedanxiety. ¹¹ One study evaluated the effects of massage therapy done with essential oils on people suffering from anxiety and/or depression while undergoing treatment for cancer. ¹² The treatment did appear to provide some short-term benefits.

Cigarette Addiction

A controlled study suggests that inhalation of black pepper vapor may reduce the craving for cigarettes. ¹³ In this trial, a total of 48 smokers used cigarette substitute devices that delivered black pepper vapor, menthol, or no fragrance. The results showed that use of the black pepper-based dummy cigarette reduced symptoms of craving for the first morning cigarette.

Tension Headaches

Weak evidence hints that peppermint oil applied to the forehead might relieve tension headaches . ¹⁴ A topical ointment known as Tiger Balm has also shown promise for headaches. Tiger Balm contains camphor, menthol, cajaput, and clove oil. A double-blind study enrolling 57 people with acute tension headache compared the application of Tiger Balm to the forehead against placebo ointment as well as the drug acetaminophen (Tylenol). ¹⁵ The placebo ointment contained mint essence to make it smell similar to Tiger Balm. Real Tiger Balm proved more effective than placebo and just as effective and more rapid-acting than acetaminophen.

Other Conditions

Weak evidence suggests that inhaled peppermint oil might relieve postsurgical nausea . ¹⁶ Inhaled peppermint oil may also be helpful for relieving mucus congestion of the lungs and sinuses; however, there is only weak supporting evidence for this use. ¹⁷ In one study, abdominal massage with lavender, rose, and clary sage reduced menstrual pain to a greater extent than an almond oil placebo. ¹⁸ In another study, acupressure combined with lavender, rosemary, and peppermint aromatherapy was more effective than acupressure alone for treating the shoulder pain caused by a certain form of stroke . ¹⁹ Controlled studies have evaluated proprietary-inhaled aromatherapy preparations for treating the common cold ²⁰ and preventing flare-ups of chronic bronchitis , ²¹ but the results were marginal at best.

A controlled study evaluated rosemary and also lavender aromatherapy for enhancing memory and mental function , but found results that were mixed at best. ²² In a large, controlled trial (more than 600 participants), lavender oil in bathwater failed to improve pain after childbirth . ²³ However, lavender oil has shown a bit of promise for insomnia . ²⁴ Another large study failed to find aromatherapy more helpful than placebo for reducing psychological distress among people undergoing radiation therapy for cancer . ²⁵

Oral Use of Essential Oils

Respiratory Problems

Eucalyptus is a standard ingredient in cough drops and cough syrups, as well as in oils added to humidifiers. A standardized combination of eucalyptus oil plus two other essential oils has been studied for effectiveness in a variety of respiratory conditions. This combination therapy contains cineole from eucalyptus, d-limonene from citrus fruit, and alpha-pinene from pine. Because these oils are all in a chemical family called monoterpenes, the treatment is called essential oil monoterpenes .

Most, though not all, double-blind studies, some of which were quite large, indicate that oral use of essential oil monoterpenes can help colds , sinus infections, and acute bronchitis . ^{26 27 28 29 30 31} For example, a 3-month, double-blind trial of 246 people with chronic bronchitis found that consumption of essential oil monoterpenes helped prevent the typical worsening of chronic bronchitis that occurs during the winter. ³² Another study evaluated 676 male and female outpatients with acutebronchitis and found that essential oil monoterpenes were more effective than placebo. ³³ Essential oil monoterpenes are thought to work by thinning mucus, though they may have other effects.

Eucalyptus oil alone may be helpful for respiratory problems as well. In a double-blind trial, 32 people on steroids to control severe asthma (steroid-dependent asthma) were given either placebo or essential oil of eucalyptus for 12 weeks. ³⁴ The results showed that people using eucalyptus were able to gradually reduce their steroid dosage to a greater extent than those taking placebo. In another study, eucalyptus oil proved helpful for the treatment of "head cold" symptoms (technically, nonpurulent rhinosinusitis). ³⁵ In this double-blind, placebo-controlled study of 152 people, use of cineole at a dose of 200 mg three times daily markedly improved cold symptoms as compared to placebo.

Digestive Problems

A double-blind, placebo-controlled study of 39 people found that an enteric-coated peppermint- caraway oil combination taken 3 times daily by mouth for 4 weeks significantly reduced dyspepsia pain as compared to placebo. ³⁶ Of the treatment group, 63.2% of participants were pain-free after 4 weeks, compared to 25% of the placebo group. Similarly, results from a double-blind comparative study of 118 people suggest that the combination of peppermint and caraway oil is comparably effective to the standard drug cisapride, which is no longer available. ³⁷ After 4 weeks, the herbal combination reduced dyspepsia pain by 69.7%, whereas the conventional treatment reduced pain by 70.2%.

A preparation of peppermint, caraway, fennel, and wormwood oil was compared to the drug metoclopramide in a double-blind study enrolling 60 people. ³⁸ After 7 days, 43.3% of the treatment group was pain-free, compared to 13.3% of the metoclopramide group.

Oral use of peppermint oil has shown considerable promise for irritable bowel syndrome . However, most studies were relatively poorly designed. ³⁹

Other Oral Uses for Essential Oils

One study found preliminary evidence that a complicated mixture of essential oils (taken by gargle or mouth spray) might be helpful for reducing snoring symptoms. ⁴⁰ A thorough review of 11 randomized, controlled trials found that the use of mouth rinses containing essential oils is effective against gingivitis and dental plaque formation when used in combination with regular oral hygiene. ⁴¹

Topical Use of Essential Oils

Tea tree oil , an essential oil from the plant Melaleuca alternifolia, possesses antibacterial and antifungal properties. ⁴² It has been tried for various forms of vaginal infection , but the only supporting evidence for this use comes from an uncontrolled trial . ⁴³ There is slightly better evidence to support the use of tea tree oil for the treatment of athlete’s foot , fibromyalgia , and related fungal infections. ⁴⁴ One open study hints that oil of bitter orange , a flavoring agent from dried bitter orange peel, might have some effectiveness against athlete's foot when applied topically. ⁴⁵ Topical essential oils might be helpful for alopecia areata , a form of hair loss that can occur in men and women. In a 7-month, double-blind, placebo-controlled trial, 84 people with alopecia areata massaged either essential oils or a non-treatment oil into their scalps each night for 7 months. ⁴⁶ The treatment oil contained essential oils of thyme, rosemary , lavender, and cedarwood. The results showed that 44% of the treatment group experienced new hair growth, compared to only 15% of the control group.

Cineol (from eucalyptus) has shown some effectiveness for repelling mosquito bites . ⁴⁷ In a preliminary double-blind blind study, coriander oil applied topically protected the skin from the harmful effects of ultraviolet radiation more than a placebo cream ( photosensitivity ). ⁴⁸ People with fibromyalgia experience muscle pain in many parts of the body. A pilot double-blind study found that topical application of a proprietary mixture containing camphor oil, rosemary oil, eucalyptus oil, peppermint oil, aloe vera oil, lemon oil, and orange oil could reduce fibromyalgia pain more effectively than placebo. ⁴⁹ Another study found that massage combined with the topical application of ginger and orange essential oils was no better than massage plus olive oil at relieving pain, reducing stiffness, or improving function in patients with osteoarthritis of the knee. ⁵⁰ One study in rats indicates that under some circumstances essential oils instilled into the ear may be able to penetrate the eardrum. ⁵¹ While this supports the idea of treating otitis media (the typical ear infection of childhood) with herbal ear drops, it also raises concerns about possible harm to the middle ear.

Finally, for literally hundreds of essential oils, test tube studies show antimicrobial effects (activity against fungi, bacteria, and/or viruses). ⁵² Presumably, essential oils are part of the plants own defenses against such organisms. However, contrary to widespread claims, such studies do notindicate that these essential oils can work as antibiotics; innumerable substances kill microorganisms in the test tube but not when taken orally by people. (Bleach would be one good example!)

It’s not clear how inhaled aromatherapy works (assuming that it does). Possibly, enough is inhaled through the lungs to produce meaningful concentrations of herbal chemicals in the body. It is also possible that aromatherapy might work through the olfactory centers of the brain. In other words, a pleasant fragrance may be soothing, refreshing, calming, and stimulating—hardly a revolutionary concept!

For all intents and purposes, licensure in aromatherapy does not exist. For this reason, the best way to find a qualified practitioner is to seek a referral from a healthcare professional.

1. Howard S, Hughes BM. Expectancies, not aroma, explain impact of lavender aromatherapy on psychophysiological indices of relaxation in young healthy women. Br J Health Psychol. 2007 Sep 7. [Epub ahead of print]
2. Cooke B, Ernst E. Aromatherapy: a systematic review. Br J Gen Pract. 50(455):493-6.
3. Holmes C, Hopkins V, Hensford C, MacLaughlin V, Wilkinson D, Rosenvinge H. Lavender oil as a treatment for agitated behaviour in severe dementia: a placebo controlled study. Int J Geriatr Psychiatry. 17(4):305-8.
4. Holmes C, Hopkins V, Hensford C, MacLaughlin V, Wilkinson D, Rosenvinge H. Lavender oil as a treatment for agitated behaviour in severe dementia: a placebo controlled study. Int J Geriatr Psychiatry. 17(4):305-8.
5. Lin PW, Chan WC, Ng BF, Lam LC. Efficacy of aromatherapy (Lavandula angustifolia) as an intervention for agitated behaviours in Chinese older persons with dementia: a cross-over randomized trial. Int J Geriatr Psychiatry. 22(5):405-10.
6. Snow LA, Hovanec L, Brandt J. A controlled trial of aromatherapy for agitation in nursing home patients with dementia. J Altern Complement Med. 2004;10:431-437.
7. Ballard CG, O'Brien JT, Reichelt K, Perry EK. Aromatherapy as a safe and effective treatment for the management of agitation in severe dementia: the results of a double-blind, placebo-controlled trial with Melissa. J Clin Psychiatry. 63(7):553-8.
8. Cooke B, Ernst E. Aromatherapy: a systematic review. Br J Gen Pract. 50(455):493-6.
9. Morris N, Birtwistle S, Toms M. Anxiety reduction by aromatherapy: anxiolytic effects of inhalation of geranium and rosemary. Int J Aromatherapy. 1995;7:33-39.
10. Wiebe E. A randomized trial of aromatherapy to reduce anxiety before abortion. Eff Clin Pract. 3(4):166-9.
11. Burnett KM, Solterbeck LA, Strapp CM. Scent and mood state following an anxiety-provoking task. Psychol Rep. 95(2):707-22.
12. Wilkinson SM, Love SB, Westcombe AM, Gambles MA, Burgess CC, Cargill A, Young T, Maher EJ, Ramirez AJ. Effectiveness of aromatherapy massage in the management of anxiety and depression in patients with cancer: a multicenter randomized controlled trial. J Clin Oncol. 25(5):532-9.
13. Rose JE, Behm FM. Inhalation of vapour from black pepper extract reduces smoking withdrawal symptoms. Drug Alcohol Depen. 1994;34:225-229.
14. Göbel H, Fresenius J, Heinze A, Dworschak M, Soyka D. [Effectiveness of Oleum menthae piperitae and paracetamol in therapy of headache of the tension type] Nervenarzt. 67(8):672-81.
15. Schattner P, Randerson D. Tiger Balm as a treatment of tension headache. A clinical trial in general practice. Aust Fam Physician. 25(2):216, 218, 220 passim.
16. Tate S. Peppermint oil: a treatment for postoperative nausea. J Adv Nurs. 26(3):543-9.
17. European Scientific Cooperative on Phytotherapy. Aetheroleum (peppermint oil). Menthae Piperitae. Exeter, UK: ESCOP; 1996-1997:1-6. Monographs on the Medicinal Uses of Plant Drugs, Fascicule 3.
18. Han SH, Hur MH, Buckle J, Choi J, Lee MS. Effect of aromatherapy on symptoms of dysmenorrhea in college students: A randomized placebo-controlled clinical trial. J Altern Complement Med. 12(6):535-41.
19. Shin BC, Lee MS. Effects of aromatherapy acupressure on hemiplegic shoulder pain and motor power in stroke patients: a pilot study. J Altern Complement Med. 13(2):247-51.
20. Cohen BM, Dressler WE. Acute aromatics inhalation modifies the airways. Effects of the common cold. Respiration. 43(4):285-93.
21. Ferley JP, Poutignat N, Zmirou D, et al. Prophylactic aromatherapy for supervening infections in patients with chronic bronchitis. Statistical evaluation conducted in clinics against a placebo. PhytotherapyResearch. 1989;3:97-100.
22. Moss M, Cook J, Wesnes K, Duckett P. Aromas of rosemary and lavender essential oils differentially affect cognition and mood in healthy adults. Int J Neurosci. 113(1):15-38.
23. Dale A, Cornwell S. The role of lavender oil in relieving perineal discomfort following childbirth: a blind randomized clinical trial. J Adv Nurs. 19(1):89-96.
24. Lewith GT, Godfrey AD, Prescott P. A single-blinded, randomized pilot study evaluating the aroma of Lavandula augustifolia as a treatment for mild insomnia. J Altern Complement Med. 11(4):631-7.
25. Graham PH, Browne L, Cox H, Graham J. Inhalation aromatherapy during radiotherapy: results of a placebo-controlled double-blind randomized trial. J Clin Oncol. 21(12):2372-6.
26. Sengespeik HC, Zimmermann T, Peiske C, et al. Myrtol standardized in the treatment of acute and chronic respiratory infections in children. A multicenter post-marketing surveillance study [in German; English abstract]. Arzneimittelforschung. 1998;48:990-994.
27. Federspil P, Wulkow R, Zimmermann T. Effects of standardized Myrtol in therapy of acute sinusitis—results of a double-blind, randomized multicenter study compared with placebo [in German; English abstract]. Laryngorhinootologie. 1997;76:23-27.
28. Behrbohm H, Kaschke O, Sydow K. Effect of the phytogenic secretolytic drug Gelomyrtol forte on mucociliary clearance of the maxillary sinus [in German; English abstract]. Laryngorhinootologie. 1995;74:733-737.
29. Meister R, Wittig T, Beuscher N, et al. Efficacy and tolerability of Myrtol standardized in long-term treatment of chronic bronchitis. A double-blind, placebo-controlled study. Study Group Investigators. Arzneimittelforschung. 1999;49:351-358.
30. Matthys H, de Mey C, Carls C, Ryś A, Geib A, Wittig T. Efficacy and tolerability of myrtol standardized in acute bronchitis. A multi-centre, randomised, double-blind, placebo-controlled parallel group clinical trial vs. cefuroxime and ambroxol. Arzneimittelforschung. 50(8):700-11.
31. Ulmer WT, Schott D. Chronic obstructive bronchitis. Effect of Gelomyrtol forte in a placebo-controlled double-blind study [in German; English abstract]. Fortschr Med. 1991;109:547-550.
32. Meister R, Wittig T, Beuscher N, et al. Efficacy and tolerability of Myrtol standardized in long-term treatment of chronic bronchitis. A double-blind, placebo-controlled study. Study Group Investigators. Arzneimittelforschung. 1999;49:351-358.
33. Matthys H, de Mey C, Carls C, Ryś A, Geib A, Wittig T. Efficacy and tolerability of myrtol standardized in acute bronchitis. A multi-centre, randomised, double-blind, placebo-controlled parallel group clinical trial vs. cefuroxime and ambroxol. Arzneimittelforschung. 50(8):700-11.
34. Juergens UR, Dethlefsen U, Steinkamp G, et al. Anti-inflammatory activity of a 1.8-cineol (eucaplyptol) in bronchial asthma: a double-blind placebo-controlled trial. Respir Med. 2003;97:250-256.
35. Kehrl W, Sonnemann U, Dethlefsen U. Therapy for acute nonpurulent rhinosinusitis with cineole: results of a double-blind, randomized, placebo-controlled trial. Laryngoscope. 114(4):738-42.
36. May B, Kuntz HD, Kieser M, Köhler S. Efficacy of a fixed peppermint oil/caraway oil combination in non-ulcer dyspepsia. Arzneimittelforschung. 46(12):1149-53.
37. Madisch A, Heydenreich CJ, Wieland V, Hufnagel R, Hotz J. Treatment of functional dyspepsia with a fixed peppermint oil and caraway oil combination preparation as compared to cisapride. A multicenter, reference-controlled double-blind equivalence study. Arzneimittelforschung. 49(11):925-32.
38. Westphal J, Horning M, Leonhardt K. Phytotherapy in functional upper abdominal complaints. Results of a clinical study with a preparation of several plants. Phytomedicine. 1996;2:285-291.
39. Pittler MH, Ernst E. Peppermint oil for irritable bowel syndrome: a critical review and metaanalysis. Am J Gastroenterol. 93(7):1131-5.
40. Prichard AJ. The use of essential oils to treat snoring. Phytother Res. 18(9):696-9.
41. Patel RM, Malaki Z. The effect of a mouth rinse containing essential oils on dental plaque and gingivitis. Evid Based Dent. 2008;9:18-19.
42. Williams LR, Home VN, Zhang X, et al. The composition and bactericidal activity of oil of Melaleuca alternifolia (tea tree oil). Int J Aromather. 1989;1:15-17.
43. Pea EF. Melaleuca alternifolia oil. Its use for trichomonal vaginitis and other vaginal infections. Obstet Gynecol. 1962;19:793-795.
44. Tong MM, Altman PM, Barnetson RS. Tea tree oil in the treatment of tinea pedis. Australas J Dermatol. 33(3):145-9.
45. Ramadan W, Mourad B, Ibrahim S, Sonbol F. Oil of bitter orange: new topical antifungal agent. Int J Dermatol. 35(6):448-9.
46. Hay IC, Jamieson M, Ormerod AD. Randomized trial of aromatherapy. Successful treatment for alopecia areata. Arch Dermatol. 134(11):1349-52.
47. Traboulsi AF, El-Haj S, Tueni M, Taoubi K, Nader NA, Mrad A. Repellency and toxicity of aromatic plant extracts against the mosquito Culex pipiens molestus (Diptera: Culicidae). Pest Manag Sci. 61(6):597-604.
48. Reuter J, Huyke C, Casetti F, Theek C, Frank U, Augustin M, Schempp C. Anti-inflammatory potential of a lipolotion containing coriander oil in the ultraviolet erythema test. J Dtsch Dermatol Ges. 6(10):847-51.
49. Ko GD, Hum A, Traitses G, Berbrayer D. Effects of topical O24 essential oils on patients with fibromyalgia syndrome: a randomized, placebo controlled pilot study. J Musculoskelet Pain. 2007;15:11-19.
50. Yip YB, Tam AC. An experimental study on the effectiveness of massage with aromatic ginger and orange essential oil for moderate-to-severe knee pain among the elderly in Hong Kong. Complement Ther Med. 2008;16:131-1388.
51. Kristinsson KG, Magnusdottir AB, Petersen H, Hermansson A. Effective treatment of experimental acute otitis media by application of volatile fluids into the ear canal. J Infect Dis. 191(11):1876-80.
52. Pattnaik S, Subramanyam VR, Bapaji M, Kole CR. Antibacterial and antifungal activity of aromatic constituents of essential oils. Microbios. 89(358):39-46.