Does Oil Of Oregano Kill Good Bacteria

In this brief article we will answer the question, “does oil of oregano kill good bacteria?” We will also highlight the nutritional profile and health benefits of oregano oil and will guide you about its proper dosage and potential risks. 

Does Oil Of Oregano Kill Good Bacteria?

The simple answer is no, oil of oregano does not kill good bacteria. When oregano oil is used for treating bacterial infections, its antibacterial compound carvacrol only destroys the harmful ones. Oregano oil contains carvacrol, a plant metabolite classified as a terpenoid. Carvacrol has shown the ability to inhibit growth and the adhesion of gut pathogens and to have strong antibacterial activity, whilst, at the same time, enhancing the proliferation and adhesion of probiotic bacteria, which are related to promote a healthy gut microbiota (1).

Numerous studies have demonstrated that oregano oil has powerful antibacterial properties, and is even effective against antibiotic-resistant strains of bacteria such as methicillin-resistant Staphylococcus aureus (MRSA). It has antibacterial effect also against Salmonella spp, Escherichia coli and Bacillus cereus, which are important examples of bacteria that affect the quality and safety of food (2).

In a particular study investigating the antibacterial properties of various essential oils, oregano oil stood out as the most potent against bacterial growth. Because of this trait, topical oregano oil is also used effectively for healing and treating wounds. The most important component, carvacrol, has higher antibacterial action than sulfanilamide, a synthetic antibacterial drug (2).

This is why people have been using oregano oil to treat various infections over the years, including sinus and respiratory problems. Moreover, doctors used oregano oil to treat many diseases before modern medicines were invented. 

What Makes Oregano Oil Good For Health?

Oregano is the name used to refer to a great variety of plants that share a particular flavor and odor. At least 61 species and 17 genera belonging to six different botanical families are known as oregano (3). Oil of Oregano is obtained from the leaves of the oregano plant and has a distinctly bitter taste. It has been a significant part of folk medicine for centuries and even today, a lot of people use oregano oil to treat infections, especially the common cold. Essential oils of oregano are very complex mixtures of compounds, in which the major constituents are terpenes, generally mono- and sesquiterpenes. The principal terpenes identified in the different species of oregano are carvacrol, thymol, γ-terpinene and p-cymene; while terpinen-4-ol, linalool, β-myrcene, trans-sabinene hydrate, and β-caryophyllene are also present (3).

Research investigating the possible health benefits of oregano oil has confirmed that it possesses the following attributes (3):

  • Antimicrobial (antibacterial, antifungal, and antiviral)
  • Antioxidant (stops free radicals from damaging cells and causing serious illnesses)
  • Anti-inflammatory 
  • Antidiabetic
  • Cancer suppressant 
  • anti-hypertensive properties
  • Positive effect on the cardiovascular health

Oregano oil contains beneficial compounds known as phenols, terpenoids, and terpenes, which underlie its various health benefits and also give it its distinct smell. These include: 

  • Carvacrol, the majorly occurring phenol in oregano that has been found to inhibit the growth of various types of bacteria as well as drug-resistant varieties. 
  • Thymol, the natural antifungal in oregano that supports the immune system and protects against toxins 
  • Rosmarinic acid, a potent antioxidant that protects against cell damage from free radicals

Nutritional Profile 

A single teaspoon of dried oregano leaves contains: 

  • 2.65 calories 
  • 0.09 grams of protein
  • 0.04 grams of fat
  • 0.69 grams of carbohydrates 
  • 0.42 grams of fiber
  • 0.04 gram of sugar
  •  Beta-carotene
  •  Magnesium
  •  Calcium
  •  Potassium
  •  Phosphorus 
  •  Folate
  • Iron

Oregano is also rich in vitamin K which is vital for bone health, blood clotting,  and regulating blood sugar levels. 

How Much Oil Of Oregano Should You Take?

According to functional health experts, the recommended dosage of oregano oil should not exceed 50 to 80 milligrams, i.e. two or three drops of oil per dose. It’s better to use medicinal formulations that contain about 80 percent carvacrol.

Health experts also suggest taking oregano oil via pills or capsules since it has a very unpleasant and bitter flavor. But if you don’t mind the taste, you can also consume the oil directly; mix two drops with a teaspoon of olive oil. 

Remember that using oil of oregano directly can aggravate the mucous linings of the throat, esophagus, and stomach. This is why it shouldn’t simply be taken with water. Using a carrier oil such as olive oil as mentioned above can prevent irritation of the membranes.

There is not much information available regarding the use of oregano oil and its potential toxicity doses. Some studies done on mice using 50, 100 or 200 mg/kg body weight per day of oregano oil for 90 days caused no increased occurrences of DNA strand breaks detected in the tissues analyzed, that is, it did not cause genotoxicity effect. In another study, mice were fed with doses of oregano oil of 0, 50, 100 or 200 mg/kg bw per day of oregano oil during 90 days. Gross necropsy revealed no changes in organ weights in the treated groups compared to the control group except for a slight increase in kidney weight for the 200 mg/kg bw per day females when compared to the 100 mg/kg bw per day female group and a significant increase in the ovary weights for the 50 mg/kg bw per day females. Histopathological analyses of the liver, kidney, intestine, stomach, lung, heart, and testicle or ovary found no differences between the control and treatment groups (4). These studies indicate that there could be a high tolerance for oregano oil. However, since there are no safe information on the toxicity of this oil for humans, it should be consumed with caution, especially in the case of children and pregnant homen. In 2015, the Flavor and Extract Manufacturers Association (FEMA) recognized as safe the use of oregano oil as the levels of intended use as flavoring ingredients (4).

For How Long Should You Use Oregano Oil?

You shouldn’t use oregano oil for more than a week. Start with one dose thrice a day for the first two days, then cut it down to one dose twice a day. 

If your symptoms do not improve after seven days, discontinue use and consult a doctor.

Is There Any Risk Of Using Oregano Oil?

Yes. Since oregano oil contains many powerful ingredients, you must consult a doctor before using it directly or in supplement form (5). 

Here are some risks involved with using oregano oil either in pill/capsule form or topically:

  • Toxicity – using oregano oil in large doses for long periods can cause toxicity and may even be lethal. This is why you should always stick to the recommended dosages. More research on the toxic effects of oregano oil on humans is underway.
  • Skin Irritation – applying oregano oil topically might irritate sensitive skin. Never use undiluted oregano oil directly on the skin. Always mix it with a carrier oil, or do a patch test to make sure there aren’t any adverse effects. More research is underway.
  • Pregnancy and Lactation – these effects remain inconclusive; however, if you are pregnant or breastfeeding, it’s best to avoid using oregano oil. 


In this brief article we answered the question, “does oil of oregano kill good bacteria?” We also highlighted the nutritional profile and health benefits of oregano oil and guided you about its proper dosage and potential risks. 

If you have any more questions or comments please let us know.


  1. Gutiérrez, S., Morán, A., Martínez-Blanco, H. et al. The Usefulness of Non-Toxic Plant Metabolites in the Control of Bacterial Proliferation. Probiotics & Antimicro. Prot., 2017, 9, 323–333
  2. Guimarães, Aline Cristina, et al. Antibacterial activity of terpenes and terpenoids present in essential oils. Molecules, 2019, 24, 2471.
  3. Leyva-López, Nayely, et al. Essential oils of oregano: Biological activity beyond their antimicrobial properties. Molecules, 2017, 22, 989.
  4. Cohen, Samuel M., et al. FEMA GRAS assessment of natural flavor complexes: Origanum oil, thyme oil and related phenol derivative-containing flavoring ingredients. Food Chem Toxicol, 2021, 155, 112378.
  5. Vostinaru, Oliviu, Simona Codruta Heghes, and Lorena Filip. Safety profile of essential oils. Essential Oils-Bioactive Compounds, New Perspectives and Applications, 2020, 1-13.