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The Science Behind the Oils: A Summary of Some Research Facts

©Copyright 2012 Aroma Shield LLC

Essential oil therapy long ago emerged from the status of tradition and folklore. A quick Internet search of the thousands of research projects summarized on PUBMED, the National Institute of Health website for health and medical research, (, reveals that since 1990, many hundreds of studies have been conducted, evaluating and confirming the therapeutic properties of essential oils.

Unfortunately, the sponsors of much of this research are pharmaceutical companies, seeking not to validate the efficacy of essential oils, but rather to isolate chemical constituents in essential oils which they can then reformulate, patent and sell as drugs. Regardless of their motivation, the research on essential oils is showing startling potential in the arena of health and healing.

In January of 2007, the scientific publication, Phytotherapy Research published a 15-page article entitled, “Pharmaceutical and Therapeutic Potentials of Essential Oils and Their Individual Volatile Constituents: A Review.” This extremely well-documented article, citing 270 different studies, provided an excellent review of the many, significant possibilities for powerful healing with essential oils. The article was authored by Dr. Amr E. Edris of the Aroma and Flavor Chemistry Department at the National Research Center in Cairo, Egypt. While this excellent article does not cover all the ways in which essential oils are being researched for their therapeutic value, it does cover and document enough science to make it clear that essential oils are now being taken very seriously by the medical research community. The following summary points are taken from that article.

I. Skin Penetration/Absorption
a. At least seven studies have shown that the lipophilic characteristics and terpene constituents in essential oils make them able to penetrate the skin and enter interior tissues very rapidly.1,2
b. Oral intake is not suitable for some drugs due to stomach acidity and liver metabolism, but by combining them with essential oils, they can be administered topically.3
c. Unlike synthetic skin penetration enhancers, essential oils are much less expensive and far less toxic, yet they are just as effective in facilitating transdermal drug delivery.4
d. Some oils which have been shown effective in enhancing skin permeability include peppermint, sweet basil, niaouli and eucalyptus.5,6

II. Antioxidant Enhancement
a. Free radicals cause oxidation of biomolecules in proteins, fats and DNA. This creates the environment of degeneration that leads to aging, arteriosclerosis, cancer, Alzheimer’s disease, Parkinson’s disease, diabetes, asthma, etc. In a healthy body, the immune system can quench free radicals present in almost all cells. When free radical production exceeds the body’s capacity to remove them, a condition arises known as ‘oxidative stress.’ In this situation an external supply of antioxidants is necessary to regain the balance.7

b. Many essential oils, as natural sources of phenolic components, have been shown to be effective free radical scavengers. The following oils were found, in order, to have particularly effective antioxidant properties: clove bud, cinnamon bark, nutmeg, basil, oregano, and thyme. Their antioxidant activity was attributed to a high content of thymol and carvacrol.8
c. Other essential oils with proven antioxidant activity include melissa, tea tree, citronella and peppermint.9,10

III. Antibacterial Properties
a. Research has repeatedly demonstrated that essential oils are antibacterial agents against a wide variety of pathogenic bacterial strains, including: listeria, salmonella, e. coli, shigella, bacillus, and staphylococcus.11
b. Figuring prominently among the most antibacterial essential oils are oregano, and thyme, due to their carvacrol and thymol constituents.12
c. Another prominent antibacterial essential oil is tea tree oil, which has been shown in hospital trials to reduce infection transmission between staff and patients through use of a tea tree-based hand lotion that, unlike conventional antiseptics, did not create dermatological problems or affect the protective bacterial flora of the skin.13
d. Essential oils, surprisingly, have been shown to be safe and effective against many varieties of antibiotic-resistant bacteria, including MRSA. Tea tree, oregano, peppermint and spearmint have all been successfully tested against multidrug-resistant pathogens.14
e. Helicobacter pylori, which has been identified as a primary cause of stomach ulcers, can be controlled by essential oils containing carvacrol, isoeugenol, citral and sabinene. This would include essential oils of oregano, thyme, basil, lemongrass and clove bud.15
f. Essential oils were shown to be particularly effective when used orally as a mouthwash to control and eliminate pathogenic bacteria in the mouth and teeth. Essential oils mouthwashes were shown to be as effective as chlorhexidine in their anti-plaque and anti-gingivitis activity.16
g. Essential oils kill bacteria by penetrating their cell membranes, rendering them more permeable, ultimately resulting in a leakage of vital cell contents and cell death.17

IV. Antiviral Discoveries
a. Essential oils can be an alternative to synthetic antiviral drugs because they are in many cases equally or more effective and they are much less toxic to the body.18
b. Essential oils with citral and citronellal (melissa and citronella) have been shown to kill and retard Herpes simplex virus 2; and lemongrass essential oil showed effectiveness in killing Herpes simplex virus 1 even at very high dilutions.19,20
c. Peppermint, tea tree and eucalyptus oils have also demonstrated virucidal properties against HSV-1 and HSV2.21
d. Encouraging research is on-going with essential oils versus other viral strains, including those involved with influenza, pneumonia and hepatitis.

V. Inhalation Impact
a. Inhalation of essential oils has a significant role in controlling the central nervous system.22
b. The essential oils of jasmine, cedarwood and lavender have been shown to have a tranquilizing effect on the brain upon inhalation.23,24
c. Inhalation of essential oils can significantly change the activity of the sympathetic nervous system. For example, the inhalation of black pepper, sweet fennel or grapefruit oils resulted in a 1.5 to 2.5-fold increase in relative sympathetic activity. By contrast, inhalation of rose oil or patchouli oil cause a 40% decrease in relative sympathetic activity.25
d. Inhalation of lavender, peppermint, rosemary and clary sage essential oils, among others, can significantly decrease symptoms associated with anxiety and stress.26
e. On a hormonal level, inhalation of black pepper oil induced a 1.7-fold increase in adrenaline level, while inhalation of rose oil resulted in a 30% decrease in adrenaline level.27
f. Inhalation of peppermint has been shown to be efficacious in the treatment of pulmonary tuberculosis.28

VI. Topical Effects
a. Essential oils, topically applied, showed positive effects on lung mucus clearance in patients with chronic airway obstruction.29
b. Lavender applied topically in a gel had a significant effect of improving mood and making people feel more relaxed.30
c. Inflammatory diseases, such as allergy, rheumatism and arthritis are often alleviated using essential oil massage therapy.31
d. Allergy symptoms have been relieved by tea tree, lavender and geranium essential oils, mainly due to a suppression of histamine release.32,33

VII. Cardiovascular Benefit
a. Atherosclerosis is a process in which deposits of plaque (oxidized low density lipoproteins or LDLs) build up in the innermost layer of the artery. This plaque can eventually significantly reduce blood flow, leading to cardiovascular disease. Atherosclerosis can be slowed or inhibited by preventing the oxidation of LDLs using a high daily intake of antioxidants.34
b. Certain essential oils and their volatile constituents can effectively inhibit the oxidation of both the lipid part and the protein part of LDL. Oils rich in phenols such as clove bud and thyme have the highest antioxidative activity against LDL oxidation.35
c. Also, the monoterpene ɣ-terpinene was also found to inhibit LDL oxidation. Tea tree oil and sweet marjoram oil are rich sources of ɣ-terpinene, and it is also found in some citrus peel oils such as tangerine and lemon.36
d. Some essential oils can actually lower blood triglyceride levels. In one study, dill seed oil reduced triglyceride levels by almost 42%.37
e. One of the consequences of atherosclerosis is hypertension (high blood pressure) and certain essential oils have been shown to have a neutralizing effect on hypertension in the laboratory. Intravenous administration of the essential oil of basil induced an immediate and significant lowering of blood pressure and slowing of the heart beat. This resulted from its vasodilator effects, acting directly on vascular smooth muscle.38
f. Thrombosis (blood clots) is a problem associated with cardiovascular disease and can result in stroke as well as heart attack. Synthetic blood thinners (antiplatelet agents) are often prescribed for therapy in cardiovascular disease to prevent clotting.  Many blood thinners have negative and even dangerous side effects. Certain essential oils, however, including clove bud and lavender, have been shown to be effective antiplatelet agents without negative side effects.39

VIII. Anti-Cancer Properties
a. Most cancer chemotherapy makes use of highly cytotoxic drugs that target proliferating cancer cell populations. These toxic drugs are non- discriminatory meaning they attack normal cells as well as cancerous ones, leading to severe side effects and limiting the dose of anticancer drugs that can be administered. An issue that has drawn attention to essential oils is the fact that their mechanism of action, unlike conventional chemotherapy, is at least partly discriminatory, focusing more specifically on cancer cells and having far less effect on normal cells.40
b. Essential oils have been shown to aid in the cancer fight both in preventing carcinogens from compromising DNA, and also in retarding cancer once it takes hold, either through inhibiting tumor cell reproduction or increasing the rate of tumor cell death (apoptosis). For example, monoterpenes, which are found in many essential oils, have been shown to work in both ways on breast cancer tumors.41
c. Nutmeg and lemongrass have also been shown effective in neutralizing the carcinogenic activities that cause liver and skin cancer.42,43
d. Sweet orange oil and sweet fennel essential oils have been repeatedly studied for their ability to protect against liver cancer due to their high d- limonene content.44,45
e. Sweet orange oil is also a candidate for the chemoprevention of skin cancer.46
f. ɑ-Bisabolol, a major sesquiterpene alcohol in chamomile essential oil is considered a promising inducer of apoptosis (cancer cell death) in glioma cells, one of the most malignant of human tumors.47
g. Essential oils have demonstrated cancer suppressive activity on a number of other human cancer cell lines in laboratory settings, including colon cancer, gastric
cancer, liver cancer, lung cancer, breast cancer, leukemia and others.48
h. Geraniol, an essential oil constituent found in small amounts in geranium oil and in large
ounts in palmarosa oil has been found effective in helping to retard
the growth of colon cancer.49,50
i. ɗ-Limonene, the primary ingredient in orange, lemon and spearmint oils, has been shown to induce apoptosis in stomach cancer, liver cancer and lymphoma in
experiments with rats and mice.51,52,53
j. Perillyl alcohol, found in small amounts in lavender, peppermint, spearmint and lemongrass oils, has potential as an anticancer drug because it stimulates tumors
to apoptosis, inhibits proliferation, and overcomes tumor cell resistance to chemotherapy. This action was demonstrated in research involving prostate, breast and
colon cancers.54
k. Eucalyptol, also known as 1,8 cineole, is found in high concentrations in the essential oils of eucalyptus and cardamom, and has been shown to initiate apoptosis
in leukemia cells.55


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8Tomaino A, et al. Influence of heating on antioxidant activity and the chemical composition of some spice essential oils. Food Chem, 2005, 89:549-554.

9Mimica-Dukic N, et al. Antimicrobial and antioxidant activities of Melissa officinalis essential oil. J Agric Food Chem, 2004, 52:2485-2489.

10Kim H, et al. Evaluation of antioxidant activity of Australian tea tree oil and its components. J Agric Food Chem, 2004, 52:2849-2854.

11Schmidt E, et al. Antimicrobial testing and gas chromatographic analysis of aroma chemicals. J Essential Oil Bearing Plants, 2005, 8:99-106

12Penalver P, et al. Antimicrobial activity of five essential oils against origin strains of the Enterobacteriaceae family. APMIS, 2005, 113:1-6

13Messager S, et al. Effectiveness of hand-cleansing formulations containing tea tree oil assessed ex vivo on human skin and in vivo with volunteers using European standard EN 1499. J Hosp Infect, 2005, 59:220-228

14May J, et al. Time-kill studies of tea tree oils on clinical isolates. J Antimicrob Chemother, 2000, 45:639-643

15Bergonzelli G, et al. Essential oils as components of a diet-based approach to management of Helicobacter infection. Antimicrob Agents Chemother, 2003, 47:3240-3246

16Charles C, et al. Comparative antiplaque and antigingivitis effectiveness of a chlorhexidine and an essential oil mouthrinse: 6-month clinical trial. J Clin Periodontol, 2004, 31:878-884

17Burt S. Essential oils: their antibacterial properties and potential applications in foods – a review. Int J Food Microbiol, 2004, 94:223-253

18Baqui A, et al. In vitro effects of oral antiseptics human immunodeficiency virus-1 and herpes simplex virus type 1. J Clin Periodontol, 2001, 28:610-616

19Allahverdiyev A, et al. Antiviral activity of the volatile oils of Melissa officinalis L. against Herpes simplex virus type-2. Phytomedicine 2004, 11:657-661

20Minami M, et al. The inhibitory effect of essential oils on herpes simplex virus type-1 replication in vitro. Microbiol Immunol, 2003, 47:681-684

21Schuhmacher A, Reichling J, Schnitzler P. Virucidal effect of peppermint oil on the enveloped viruses herpes simplex virus type 1 and type 2 in vitro. Phytomedicine, 2003, 10:504-510.

22Koo B, et al. Inhibitory effects of the fragrance inhalation of essential oil from Acorus gramineus on central nervous system. Biol Pharm Bull, 2003, 26:978-982

23Hossain A, et al. Fragrances in oolong tea that enhance the response of GABA receptors. Biosci Biotechnol Biochem, 2004, 68:1842-1848

24Kagawa D, et al. The sedative effects and mechanism of action of cedrol inhalation with behavioral pharmacological evaluation. Planta Med, 2003, 69:637-641

25Haze S, Sakai K, Gozu Y. Effects of fragrance inhalation on sympathetic activity in normal adults. Jpn J Pharmacol, 2002, 90:247-253

26Edris A. Pharmaceutical and Therapeutic Potentials of Essential Oils and Their Individual Volatile Constituents: A Review. Phytotherapy Research, 2007, 21:308-323

27Op. cit., Haze, et al.

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29Hasani A, et al. Effect of aromatics on lung mucociliary clearance in patients with chronic airways obstruction. J Altern Comlement Med, 2003, 9:243-249

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32Brand C, et al. Tea tree oil reduces histamine-induced edema in murine ears. Inflamm Res, 2002, 51:283-289

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37Yasdanparast R and Alavi M. Antihyperlipidaemic and antihyper-cholesterolaemic effects of anethum graveolens leaves after the removal of furocoumarins. Cytobios, 2001, 105:185-191

38Laulou S, et al. Cardiovascular effects of the essential oil of Ocimum gratissimum leaves in rats: role of the autonomic nervous system. Clin Exp Pharmocol Physiol. 2004, 1:219-225.

39Ballabenia V, et al. Novel antiplatelet and antithrombotic activities of essential oil from Lavandula hybrid Reverchon ‘grosso’. Phytomedicine. 2004, 11:596-601

40Rajesh D, Howard P. Perillyl alcohol mediated radiosensitization via augmentation of the Fas pathway in prostate cancer cells. Prostate, 2003, 57-14-23

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45Ozbek H, et al. Hepatoprotective effect of Foeniculum vulgare (Sweet fennel) essential oil. Fitoterapia, 2003, 74:317-319

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47DeAngelis L. Brain tumors. N Engl J Med, 2001, 344:114-123


49Carnesecchia S, et al. Geraniol, a component of plant essential oils, sensitizes human colonic cancer cell to 5-fluorouracil treatment. J Pharmacol Exp Ther, 2002, 301:625-630

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51Guang L, et al. D-limonene induces apoptosis of gastric cancer cells. Zhonghua Zhong Liu Za Zhi (Chi J Oncol). 2003, 25:325-327

52Kaji I, et al. Inhibition by d-limonene of experimental hepatocarcinogenesis in Sprague-Dawley rats does not involve p21(ras) plasma membrane association. Int J Cancer, 2001, 93:441-444

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55Moteki H, et al. Specific induction of apoptosis by 1,8-cineole in two human leukemia cell lines. Oncol Rep, 2002, 9:757-760