Oregano is an aromatic perennial herb that can grow to about two feet in height. It is native to the Mediterranean region but is cultivated worldwide. In addition to European oregano, there are several types of related species, including Greek/Turkish oregano (Origanum onites) and Mexican oregano (Lippia graveolens, Lippa palmeri). These should not be considered substitutes for true oregano, though they may have similar properties. The leaves as well as the volatile oil of these various species are used medicinally, but must be carefully distinguished as they are quite different.1
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1 Star For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support.
Refer to label instructions
Volatile oils from oregano have been shown to have significant antifungal action. Doctors recommend enteric-coated capsules, which break down in the intestines instead of the stomach.
Volatile oils from oregano, thyme, peppermint, tea tree, and rosemary have all demonstrated antifungal action in test tube studies.4 A recent study compared the anti-Candida effect of oregano oil to that of caprylic acid.5 The results indicated that oregano oil is over 100 times more potent than caprylic acid, against Candida. Since the volatile oils are quickly absorbed and associated with inducing heartburn, they must be taken in coated capsules, so they do not break down in the stomach but instead are delivered to the small and large intestine. This process is known as “enteric coating.” Some doctors recommend using 0.2 to 0.4 ml of enteric-coated peppermint and/or oregano oil supplements three times per day 20 minutes before meals. However, none of these volatile oils has been studied for their anti-Candida effect in humans.
Indigestion, Heartburn, and Low Stomach Acidity
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Oregano is a gas-relieving herb that may be helpful in calming an upset stomach.
Carminatives (also called aromatic digestive tonics or aromatic bitters) may be used to relieve symptoms of indigestion, particularly when there is excessive gas. It is believed that carminative agents work, at least in part, by relieving spasms in the intestinal tract.6
There are numerous carminative herbs, including European angelica root (Angelica archangelica), anise, Basil, cardamom, cinnamon, cloves, coriander, dill, ginger, oregano, rosemary, sage, lavender, and thyme.7 Many of these are common kitchen herbs and thus are readily available for making tea to calm an upset stomach. Rosemary is sometimes used to treat indigestion in the elderly by European herbal practitioners.8 The German Commission E monograph suggests a daily intake of 4–6 grams of sage leaf.9 Pennyroyal is no longer recommended for use in people with indigestion, however, due to potential side effects.
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Oregano is an herb that directly attack microbes.
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Oil of oregano has been shown to effectively inhibit the growth of Candida albicans.
A test tube study demonstrated that oil of oregano, and an extract in the oil called carvacrol in particular, inhibited the growth of Candida albicans far more effectively than a commonly employed antifungal agent called calcium magnesium caprylate.10 However, clinical studies are needed to confirm these actions in humans.
The name Oreganum is the contraction of two Greek words, oros meaning mountain and ganos meaning joy. Together the words suggest the beauty that oregano lends to the fields and hilltops on which it grows.2 Oregano was used extensively by the Greeks for conditions ranging from convulsions to heart failure. Nineteenth-century American Eclectic physicians (doctors who recommended herbal medicines) employed oregano as both a general tonic and to promote menstruation.3
This dried herb contains several constituents, including volatile oil (up to 3%), such as carvacrol, thymol, and borneol, plus flavonoids, rosmarinic acid, triterpenoids (e.g. ursolic and oleanolic acid), sterols, and vitamin A and vitamin C.11 The thymol and carvacrol contents in oregano are responsible for its antimicrobial and antifungal effects.12 A test tube study demonstrated that oil of oregano, and carvacrol in particular, inhibited the growth of Candida albicans far more effectively than a commonly employed antifungal agent called calcium magnesium caprylate.13 Clinical studies are still needed to confirm these actions in humans.
In addition to its anti-fungal action, and according to the results of another test tube study from Australia, oregano oil has a strong anti-microbial action against a wide number of bacteria, including Escherichia coli, Klebsiella pneumoniae, Salmonella enterica, and Staphylococcus aureus. 14 Other test tube studies have shown that oregano from the Mexican (Lippia) species was more effective than the prescription medication tinidazol in inhibiting the parasite giardia (Giardia duodenalis). 15 In another test tube study, volatile oils of oregano, thyme, cinnamon, and cumin were individually able to stop the growth of another food-borne pathogen called Aspergillus parasiticus. Higher concentrations of these volatile oils were also able to stop the production of aflatoxin, a potent poison from the food moldAspergillus.16 Together these facts suggest the volatile oils in oregano used during food processing have an important role in preventing the spoilage of food and in reducing the risk of ingesting harmful bacteria, fungi, and parasites. Again, these actions have not yet been confirmed by human clinical trials.
The German Commission E does not approve oregano for any medical indication.17
Dried or fresh leaf of oregano can be made into a tea by steeping 1 to 2 teaspoons (5 to 10 grams) in hot water for ten minutes. This tea can be consumed three times a day.18 The oil (50% or greater dilution) may be applied topically twice a day to areas affected by athlete’s foot or other fungal infections. The affected area should be covered by the oil with each application. The safety of the internal use of the oil has not been well studied and should be used with caution or after consulting with a healthcare professional.
Oregano leaf is very safe. The German Commission E and American Herbal Products Association both state there are no known risks with oregano leaf;19 neither of these references mentions oregano oil.
Due to the lack of human research and the highly concentrated nature of oregano volatile oil, there is potential for harm from its use; therefore, until its internal use in humans has been proven safe, it should taken with caution if not recommended by a healthcare professional.20 Volatile oils are generally considered contraindicated in pregnancy as they likely reach the baby and may cause harm.21 Topically, the volatile oil of oregano may be moderately irritating to skin and can be a potent mucous membrane irritant. It should not be applied topically to mucous membranes in greater than a 1% concentration.22 Children less than two years of age and people with damaged or very sensitive skin should not use the oil topically.23
1. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients, 2nd ed. New York: John Wiley & Sons, 1996, 398-9.
2. Grieve M. A Modern Herbal, vol II. New York: Dover Publications, 1982, 520-1.
3. Castleman M. The Healing Herbs. Emmaus, PA: Rodale Press, 1991, 275-6.
4. Hammer KA, Carson CF, Riley TV. In-vitro activity of essential oils, in particular Melaleuca alternafolia (tea tree) oil and tea tree oil products, against Candida albicans. J Antimicrobial Chemother 1998;42:591-5.
5. Stiles JC, Sparks W, Ronzio RA. The inhibition of Candida albicans by oregano. J Applied Nutr 1995;47:96-102.
6. Forster HB, Niklas H, Lutz S. Antispasmodic effects of some medicinal plants. Planta Med 1980;40:303-19.
7. Blumenthal M, Busse WR, Goldberg A, et al. (eds). The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Austin: American Botanical Council and Boston: Integrative Medicine Communications, 1998, 425-6.
8. Weiss RF. Herbal Medicine. Beaconsfield, UK: Beaconsfield Publishers Ltd, 1988, 185-6.
9. Blumenthal M, Busse WR, Goldberg A, et al. (eds). The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Austin: American Botanical Council and Boston: Integrative Medicine Communications, 1998, 198.
10. Stiles JC, Sparks W, Ronzio RA. The inhibition of Candida albicans by oregano. J Applied Nutr 1995;47:96-102.
11. Wren RC. Potter's New Cyclopedia of Botanical Drugs and Preparations. Essex, England: C.W. Daniel, 1985, 185.
12. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients, 2nd ed. New York: John Wiley & Sons, 1996, 398-9.
13. Stiles JC, Sparks W, Ronzio RA. The inhibition of Candida albicans by oregano. J Applied Nutr 1995;47:96-102.
14. Hammer KA, Carson CF, Riley TV. Antimicrobial activity of essential oils and other plant extracts. J Appl Microbiol 1999;86:985-90.
15. Ponce MM, Navarro AI, Martinez GMN, et al. In vitro effect against Giardia of 14 plant extracts. Rev Invest Clin 1994;46:343-7 [in Spanish].
16. Tantaoui EA, Beraoud L. Inhibition of growth and aflatoxin production in Aspergillus parasiticus by essential oils of selected plant materials. J Environ Pathol Toxicol Oncol 1994;13:67-72.
17. Blumenthal M, Busse WR, Goldberg A, et al. (eds). The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Boston, MA: Integrative Medicine Communications, 1998, 358-9.
18. Peirce A. Practical Guide to Natural Medicines. New York: William Morrow and Co., 1999, 476-7.
19. Blumenthal M, Busse WR, Goldberg A, et al, eds.The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Boston: Integrative Medicine Communications, 1998, 358-9.
20. McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, 1997, 80.
21. Tisserand R, Balacs T.Essential Oil Safety. New York: Churchill Livingston, 1996, 234-5.
22. Tisserand R, Balacs T. Essential Oil Safety. New York: Churchill Livingston, 1996, 156-7.
23. Tisserand R, Balacs T. Essential Oil Safety. New York: Churchill Livingston, 1996, 156-7.
Last Review: 07-08-2014
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