Oregano essential oil

Oregano tree
Oregano tree

Oregano (origanum vulgare)is a member of the Labiatae family (commonly referred to as the mint family). Its name is from the Greek word oreganos, which loosely translated means “joy of the mountains.”

Native to Mediterranean regions, such as Greece and Crete, oregano is a perennial plant with an aromatic scent. With flowers that bloom from July to September, the plant is generally 2.5ft (75 cm) high and 2–3 ft (60–90 cm) wide. Its hairy, oval-shaped leaves are approximately 1.5 in (3.75 cm) in diameter and grow opposite of one another.

Oregano essential oil is produced from the oregano plant through the process of steam distillation. There are a variety of species referred to as oregano, but only a few qualify as high grade and are suitable for making oregano essential oil.

Oregano essential oil contains the following components:
  • carvacrol (share 40–70%)
  • gamma-terpinene (8–10%)
  • p-cymene (5–10%)
  • alpha-pinene
  • myrcene
  • thymol
  • flavonoids
  • caffeic acid derivatives

It should be noted that the Physicians’ Desk Reference for Herbal Medicines, also points out that there are various chemotypes with differing essential oil composition of thymol, linalool + terpinene-4-ol, linalool, caryophyllene + germacren D, or germacren D as chief components.

However, those strains, especially ones high in thymol, are not suitable for preparing oregano essential oil intended for internal consumption. Some of these essential oils are toxic to the liver and kidney in very small quantities. However prudent, short term, topical use of these variants may be safe.

General use

Historically, Greek physicians used oregano essential oils for wounds, headaches, and venomous bites and even hemlock poisoning. It wasn’t long before its medicinal benefits were used to treat lung conditions, bronchitis, sinusitis, and cold symptoms including cough.

During the seventeenth century, it was heralded throughout Great Britain as an effective remedy for head colds. Used by physicians to induce menstruation as early as the nineteenth century, the benefits of using oregano essential oil have captured the interest of modern-day researchers.

Today, oregano essential oil has antiviral, antibacterial, antifungal, antiparasitic, and antiseptic properties.

For external use, oregano essential oil is valued as a strong analgesic and antirheumatic agent. The diluted oil (usually 5 drops essential oil to 25 drops of carrier oil, like jojoba) can even be rubbed on a toothache to relieve pain.

The oil is also believed to reduce the discomfort associated with insect bites. Its powerful anti-microbial properties are said to assist in the prevention of infections and to treat skin fungi such as athlete’s foot. It has also been used to eliminate lice infestations and intestinal worms.

Oregano as a culinary spice became popular in the United States after World War II when the soldiers returned from Italy having developed a taste for pizza spiced with oregano.

The problem is that medicinally speaking not all oregano is created equal. Growing conditions (soil, climate, rainfall, altitude) and harvesting and processing can produce variations in constituents and effects.

Having penned over ten books, Dr. Cass Ingram who is considered an expert on oregano essential oil, further explains the seriousness of mislabeled oregano oil in his book The Cure is in the Cupboard.

He states that although many companies list products such as wild oregano or oil of oregano in their catalogues, “the problem is that the commercially available oil is almost exclusively thyme oil or marjoram oil,” neither of which possesses the same medicinal properties as true oregano essential oil.

Furthermore, Ingram states that thyme oil is usually made from a non-oregano plant, such as Thymus capitus from Spain, and even though it comes from an edible herb, thyme oil may be toxic. James A. Duke, Ph.D., a leading authority on healing herbs, agrees that thyme oil can be toxic; using it can lead to serious side effects and, in some cases, even cause death.

Therefore, it is critical when using oregano essential oil to be sure that its primary component is carvacrol and not thymol. As Ingram states, “true oregano grows only under specific soil and climate conditions and cannot be reproduced in your backyard.”

Dried oregano
Dried oregano

Oregano essential oil should be made only from high-grade oregano that grows wild in the mountains of the Mediterranean. Ingram provides seven key factors to consider when determining if the oil has been derived from a high-grade oregano plant.

He suggests that it should be: 1) a wild spice, not farm-raised, 2) from a proven edible species of oregano, 3) a species high in carvacrol, 4) a type used in modern research at prestigious institutions such as Georgetown University, 5) extracted in a natural process (steam distilled), 6) free of all chemical residues, and 7) relatively low in thymol (less than 5%).

Provided that the oregano essential oil being used is authentic and high grade, there is a great deal of scientific evidence to support its medicinal properties. Indeed, several studies have shown that oregano essential oil can inhibit or destroy many strains of bacteria, fungi, and parasites.

One ambiguous study, published in the Journal of Applied Microbiology in 1999, compared 52 plant oils and extracts. Oregano essential oil was found to have significant antibacterial action against a wide number of bacteria including E coli, Staph, Salmonella enterica, and Klebsiella pneumonie, which is a pneumonia that frequently occurs in people with a weakened immune system.

The following year, the Journal of Applied Microbiology published a study by Scottish researchers that showed oregano essential oil to be effective against 25 different bacteria. Other studies, such as the one done by researchers at the University of Tennessee in 2001, also showed oregano essential oil to have powerful antibacterial properties.

Research published in the International Journal of Food Microbiology in 1988 found oil of oregano to be an excellent antifungal, completely inhibiting the growth of the nine fungi tested. Since that time, numerous research studies have been published that repeatedly show the ability of oregano essential oil to kill yeast, including Candida albicans.

In 2002, oregano essential oil was put to the test in an interesting study by researchers in Yugoslavia and the results were published in Nahrung. Among the 13 fungi tested were food poisoning, plant, animal, and human pathogenic species. Oregano essential oil high in carvacrol possessed the best and broadest antifungal properties.

A small clinical trial published in 2000 examined the effects of oregano oil in adults with intestinal parasites. Of the 14 adult participants, 11 tested positive for the intestinal parasite, Blastocystis hominis, which is known to cause diarrhea, anal itching, and weight loss.

The 11 test-positive participants took 600 mg of emulsified oregano essential oil daily for six weeks. Eight were completely free of the parasite and the remaining three participants had a reduction in parasitic presence and symptoms.


Oregano essential oil should never be used undiluted. Always dilute it in a suitable carrier oil, such as olive oil, almond oil, or v-6 mixing oil. As with any product used for medicinal purposes, it is important to read and follow the label instructions and warnings.

A skin patch test should be conducted prior to using oregano essential oil for the first time. To do this, place a small amount of diluted essential oil on the inside of your elbow and apply a bandage. Wait 24 hours to see if there is any negative reaction, such as redness or irritation, before proceeding with more extensive use

Because oregano essential oil is concentrated, a little bit goes a long way. At first, it may be wise to start out cautiously by using only 1 drop of oregano essential oil to 3 parts olive oil and massage into the affected area once or twice a day.

To topically treat fungal infections on the skin and nails, Dr. Jennifer Brett, a naturopathic physician and chair of the botanical medicine department at the University of Bridgeport College of Naturopathic Medicine in Connecticut suggests the following: Dilute 1 teaspoon oregano essential oil in 2 teaspoons olive oil and apply with a cotton swab to the affected area up to three times a day.

To treat bacterial and fungal infections in other parts of the body, 1 drop of oil may be placed in an 8-ounce glass of water or juice once or twice a day. One drop may also be placed under the tongue twice a day, but it should be mixed with 1 teaspoon of honey, maple syrup, or olive oil.

For use in the bath, mix 1 to 3 drops of diluted oregano essential oil with body gel or shampoo and add it to the bath water. As an antiseptic, the diluted oil can be used in cloths to wipe down kitchen and bathroom countertops.


Do not use oregano essential oil, either topically or internally, while pregnant.

Nursing mothers should avoid applying the oil to their nipples, because it can be difficult to wash off and may be ingested inadvertently by their infants.

During the weaning process, nursing mothers wishing to use a breast message oil that contains oregano essential oil as a method to reduce milk production should do so with caution and be sure that all the oil is removed before breast-feeding.

Because of safety issues regarding breast milk and infant care, nursing mothers should always obtain the approval of an obstetrician and/or pediatrician before using oregano essential oil either topically or internally.

Topically, oregano essential oil may be irritating to the skin, especially mucous membranes, and can cause burning. Therefore, it should always be suitably diluted, and according to Tisserand and Balacs, never applied topically to mucous membranes in concentrations greater than 1%.

They also caution that people with damaged or very sensitive skin as well as children less than two years of age should not use the oil.

Special care should be taken when using oregano essential oil internally, because many of the commercially available products are erroneously labeled and are not made from high grade oregano. In fact, many contain dangerous levels of thymol.

Some experts caution that oregano essential oil should never be taken internally, while others suggest that it is safe for internal use provided that it is suitably diluted and its source and contents are verified; it must be extracted from high grade oregano and meet seven strict requirements.

Internal use (swallowed or as a rectal suppository) should be highly restricted (ie, a few drops only of the pure essential oil per dose, and limiting duration of use to a few days to weeks) This is because essential oils represent highly concentrated extracts through distillation compared to the whole crude plant (essential oils have 100’s of times more essential oil per drop due to purification, than does fresh or dried oregano herb) And although therapeutic in small, short term doses, these oils are toxic to liver, kidneys and the nervous system if taken in excess.

Always be sure to use true oregano essential oil (containing less than 5% thymol) and not thymol oil, which should never be taken internally and used topically only with extreme caution after being diluted in a suitable carrier oil.

People with any medical condition should use oregano essential oil only after consulting with a physician.

Side effects

The use of oregano essential oil can cause skin irritation, redness, and burning. If any of these negative side effects occur, discontinue use immediately.

When used either topically or internally to treat thrush, it has the potential to decrease a nursing mother’s milk supply.

In low doses over a short period of time, oregano essential oil is considered generally safe. However, high doses may be toxic to the liver.


In general, essential oils tend to be photosensitive. To avoid this interaction, stay away from direct sunlight or sun beds after applying oregano essential oil to prevent skin burn.

Do not apply oregano essential oil after perspiring; the combination of the oil and sweat could cause irritation.