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Monograph Library

Essential Oil of Oregano: A Powerful Microbial

What kind of oregano?

The wild Turkish oregano in our oregano oil products is not the oregano spice sold in supermarkets, which is usually marjoram. Oregano, which literally translates as “delight of the mountains,” originates in the mountainous regions of the eastern Mediterranean. It is a traditional medicine of that region, having been used over the centuries for treatment and prevention of the common cold, flu and other ills. Modern research strongly corroborates the astonishing medicinal properties of this plant.

Carvacrol content and synergy

People often ask us about the carvacrol content of our oregano oil. The minimum carvacrol content of our pure oregano oil is 72%. We do not guarantee a single, unchanging percentage of carvacrol, because each batch is slightly different and can vary depending on season and climatic conditions.

Note too that studies find that it is oregano essential oil in its total synergy that is best at preventing and treating chronic infections. Which is to say that its effectiveness is not entirely a function of its carvacrol or isolated constituents, but the harmony of all constituents as they naturally occur in oregano. Thus, an oregano oil with 90+% carvacrol is not demonstrably superior, as some companies claim.

The authors of a recent research article elaborate on this point in compelling terms. They explain that, while the antimicrobial action of a given essential oil may on one level be correlated with one or two of its major components, there is mounting evidence that the effectiveness of the essential oil may not be dependent exclusively on the ratio of these components one to the other but also on their interactions with other ostensibly less important constituents in the oils.[1]

In folk medicine

Traditional cultures have long valued the therapeutic qualities of oregano. A survey of Turkish folk medicinal plants, for example, reveals that oregano is a standard plant used by local peoples for the common cold.[2] Similarly, oregano essential oil is also a traditional medicine of India for toothache, rheumatism, and earache.[3]

Therapeutic uses

The late great James Duke, a pioneer researcher in the realm of medicinal botany, assigns oregano a 2-leaf rating (on a scale ranging from 1 leaf to 3) for sinusitis. Duke describes oregano as “a member of the mint family that’s simply loaded with antiseptic compounds.”[4] Duke also rates wild oregano as having the highest concentration of antioxidants of 100 mint family plants tested.[5]

The oral use of this essential oil comes with well-established precedent. In France, for example, this way of deploying oregano oil is commonplace, and it has long been acknowledged as one of the most clinically useful remedies for a wide range of infections.[6]

In his monograph on the use of oregano essential oil, noted herbalist Allan K. Tillotson refers to carvacrol and thymol as being two therapeutically important volatile oils found in oregano. It is recognized, he explains, that they thin mucus, alleviate cough, and ease muscle spasms. This makes oil of oregano useful for the treatment of lung disorders, including pneumonia, sinus congestion, hay fever, chronic bronchitis, and rhinitis.[7] Other researchers confirm that wild oregano treats severe coughs, whooping coughs, and other respiratory issues.[8]

It has been pointed out, moreover, that oregano essential oil has potent COX-2 inhibiting properties, which render it useful for those seeking relief from arthritis and the symptoms of inflammatory disease.[9]

Meanwhile, Jean Valnet, in his book The Practice of Aromatherapy, describes how oil of oregano outperformed anti-inflammatory drugs in reversing pain and inflammation.[10]

The significance of essential oils in a world of antibiotic resistance

Today, we live in a world of increasing antibiotic resistance, a problem whose challenges could change the whole landscape of health care. As mentioned above, much revolves around a complex, orchestrated dance we often call synergy. 

The fact of the matter is that plants have a long history of evolutionary survival. Plants need to produce a complex range of antimicrobial compounds, varying both in potency and spectrum of activity, in order to meet the broad array of threats they are constantly subjected to, including not just microbes, but other pests and environmental stresses. In order to survive, a plant needs to respond to multiple bacterial and environmental targets. This they have done exquisitely well for many millions of years, time out of mind. Often, it’s the essential oil component of a plant that bears the brunt of this burden of protection. 

Which is why researchers are now turning their attention to plant sources as a potential solution to the problem of bacterial resistance.[11][12][13][14] It has been found, for example, that the essential oils of tea tree, lemongrass, geranium, thyme, and peppermint inhibit methicillin-resistant Staphylococcus (MRSA) and vancomycin-resistant Enterococcus (VRE) in vitro.[15] An Italian multicenter, parallel group, randomized human clinical trial concludes that a combination of the essential oils of clove and thyme was just as effective in the treatment of bacterial vaginosis as antibiotics.[16] Another small investigational U.S. study, conducted with four matched participants, found strikingly that staph-infected wounds actually heal faster with tea tree oil than with conventional drugs.[17] Also, in study conducted on hospital patients, an antiseptic cleansing regime consisting of tea tree was found to clear MRSA carriage on the skin about as well as an alternative standard pharmaceutical treatment. In fact, the tea tree treatment was more effective than chlorhexidine or silver sulfadiazine at clearing superficial skin sites and lesions.[18] Such information could be an important boon to hospitals, which are a breeding ground for germs of every kind.

Also, very significantly, scientists are beginning to discover that essential oils used in tandem with antibiotics serve to lower the amount of antibiotic needed for the job at hand or even to re-invigorate an antibiotic that has become ineffective. For example, in vitro research has shown that the essential oils of cinnamon and lavender, combined with the antibiotic piperacillin, reversed the resistance of E. coli bacteria to the antibiotic.[19] Another in vitro study demonstrates a strong antimicrobial synergy between amoxicillin and Origanum vulgare essential oil.[20] 

There are several mechanisms at work here. It seems that the essential oils attack the cell wall of bacteria and enable them to be destroyed.[21] As well, they inhibit the enzymes generated by the bacteria to deactivate the antibiotics and disable what’s called the efflux pumping system, which bacteria use to eliminate antibiotics before they can kill them. Also, essential oils and certain herbs (e.g. garlic, cranberry, ginseng) block what is known as the quorum sensing mechanism of bacteria.[22] Quorum sensing is simply a system of signalling that bacteria use to facilitate a coordinated defence against agents like antibiotics that are bent on their destruction. “Antiquorum sensing” serves to dampen the strength that bacteria find in numbers and renders them more docile and less virulent.[23]

The truly marvellous thing is that studies show more and more that bacteria do not develop resistance to essential oils in the same way that they do to antibiotics.[24] Researchers have actually tried to induce bacterial resistance to tea tree oil by in vitro tests with Staphylococcus aureus and Escherichia coli and observed no decrease in antimicrobial susceptibility. In this same study, it is speculated that, because the monoterpenes in essential oils are lipophilic (literally, “fat-loving”), they target the structure, function, and integrity of microbial membranes, and hence “it seems unlikely that true resistance will arise.”[25] The thinking is that plants and essential oils enjoy an evolutionary complexity that allows them to target disease-causing bacteria in multiple ways, giving them an adaptability that is lacking in man-made pharmaceuticals.

The upshot of all this is that staying healthy by natural means becomes more important today than ever before. The good news too is that the amazing phytodynamic properties of essential oils, including oil of oregano, may yet help lift us from this crisis of antibiotic resistance and pull some of our irons from the fire.


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Who is it for

Take our Oreganum Plus Capsules if you suffer from symptoms of the common cold, flu, lung disorders, sinus congestion, bronchitis or allergies

How it helps

• Featuring the essential oil of oregano
• Alleviates mucous congestion of common cold
• Relieves inflammation of sinus conditions and hay fever allergies
• With antibacterial and antiviral properties


[1] Sunita Singh et al, “Composition, In Vitro Antioxidant and Antimicrobial Activities of Essential Oil and Oleoresins Obtained from Black Cumin Seeds (Nigella sativa L),” BioMed Research International 2014, p. 7.

[2] E Tuzlac and PE Aymaz, “Turkish folk medicinal plants, Part IV: Gönen (Balıkesir),” Fitoterapia 2001 May;72(4): 323-43.

[3] AK Nadkarni, Indian Materia Medica Vol. 1, Bombay: Popular Prakashan Private Ltd.; 1976, p. 875.

[4] James Duke, The Green Pharmacy, Emmaus, Pennsylvania: Rodale Press; 1997, p. 391.

[5] Ibid, p. 59.

[6] Dan Kenner, Holistic Primary Care 2003;4(4):1.

[7] Alan K Tillotson, The One Earth Herbal Sourcebook, New York: Kensington Publishers; 2001, pp. 174-6.

[8] P Schauenberg and F Paris, Guide to Medicinal Plants, New Canaan, CT: Keats Publishing; 1977, p. 249.

[9] JB LaValle, The COX-2 Connection, Rochester, VT: Healing Arts Press; 2001, p.77.

[10] J Valnet, The Practice of Aromatherapy, New York: Destiny Books, 1980.

[11] PH Warnke et al, “The battle against multi-resistant strains: Renaissance of antimicrobial essential oils as a promising force to fight hospital-acquired infections,” Journal of Cranio-Maxillo-Facial Surgery 2009 October; 37(7): 392-7.

[12] NCC Silva and Junior A Fernandes, “Biological properties of medicinal plants: a review of their antimicrobial activity,” Journal of Venomous Animals and Toxins including Tropical Diseases 2010; 16(3): 402-413.

[13] Mohd Sayeed Akthar et al, “Antimicrobial activity of essential oils extracted from medicinal plants against the pathogenic organisms: A review,” Issues in Biological Sciences and Pharmaceutical Research 2014 January; 2(1): 001-007.

[14] RRS Nelson, “In-vitro activities of five plant essential oils against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecium,” Journal of Antimicrobial Chemotherapy 1997; 40: 305-306

[15] Sue Chao et al, “Inhibition of methicillin-resistant Staphylococcus aureus (MRSA) by essential oil,” Flavour and Fragrance Journal 2008 October; 23(6): 444-449.

[16] Francesco Sosto et al, “Controlled study on thymol + eugenol vaginal douche versus econazole in vaginal candidiasis and metronidazole in bacterial vaginosis,” Arzneimittelforschung 2011; 61)2): 126-131.

[17] KB Chin and B Cordell, “The effect of tea tree oil (Melaleuca alternifolia) on wound healing using a dressing model,” Journal of Alternative and Complementary Medicine 2013 December; 19(12): 942-5.

[18] MS Dryden et al, “A randomized, controlled trial of tea tree topical preparations versus a standard topical regimen for the clearance of MRSA colonization,” Journal of Hospital Infection 2004 April; 56(4): 283-286.

[19] PS Yap et al, “Combination of essential oils and antibiotics reduce antibiotic resistance in plasmid-conferred multidrug resistant bacteria,” Phytomedicine 2012 June; 20(8-9): 710-13.

[20] B Uzair et al, “Essential oils showing in vitro anti MRSA and synergistic activity with penicillin group of antibiotics,” Pakistan Journal of Pharmaceutical Sciences 2017 Sept; 30(5(Supplementary): 1997-2002.

[21] Mallappa Kumara Swamy et al, “Antimicrobial Properties of Plant Essential Oils against Human Pathogens and Their Mode of Action: An Updated Review,” Evidence-Based Complementary and Alternative Medicine 2016.

[22] Cf. tea tree oil. E Noumi et al, “Chromobacterium violaceum and Pseudomonas aeruginosa PAO1: Models for Evaluating Anti-Quorum Sensing Activity of Melaleuca alternifolia Essential Oil and Its Main Component Terpinen-4-ol,” Molecules 2018 October; 23(10): 2672

[23] A Ahmad et al, “The impact of plant volatiles on bacterial quorum sensing,” Letters in Applied Microbiology 2015 Jan; 60(1):8-19.

[24] Take, for example, this study on tea tree oil. Katherine A. Hammer et al, “Effects of Melaleuca alternifolia (Tea Tree) Essential Oil and the Major Monoterpene Component Terpinen-4-ol on the Development of Single- and Multistep Antibiotic Resistance and Antimicrobial Susceptibility,” Antimicrobial Agents and Chemotherapy 2012 January; 56(2): 909-915.

[25] Katherine A Hammer et al, “Effects of Melaleuca alternifolia (Tea Tree) Essential Oil and the
Major Monoterpene Component Terpinen-4-ol on the Development of Single- and Multistep Antibiotic Resistance and Antimicrobial Susceptibility,” Antimicrobial Agents and Chemotherapy 2012 Feb; 56(2): 909-15.

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