Does oil of oregano kill good bacteria?

In this brief article we will answer the question, “does oil of oregano kill good bacteria?” and discuss how oregano oil kills bacteria, as well as other effects of the oil of oregano. 

Does oil of oregano kill good bacteria?

No, oil of oregano does not kill good bacteria. On the contrary, plant compounds, such as phenolics and antioxidants, can favor the growth of probiotic bacteria, which are the bacteria that promote health.

Oregano oil contains mainly terpenoids, including carvacrol, cymene, terpinen and thymol. These compounds have shown to be effective against several pathogenic bacteria, including Listeria monocytogenes, Cronobacter and Escherichia coli (1). 

At the same time, it has been reported by studies that the same compounds that can inhibit the proliferation of harmful bacteria can help the growth and adhesion of probiotic bacteria in the human gut, improving health.

How does oil of oregano kill pathogenic bacteria?

The exact mechanism by which oregano oil and other plant metabolites are able to kill pathogenic bacteria, however, a possible explanation relies on the chemical structure of the compounds present in the oil of oregano (1,2).

As mentioned above, oregano oil contains terpenoids and polyphenols. These compounds have many hydroxyl groups (-OH) in their structures, which are able to act on the bacterial cell structure, leading to their disruption. In addition, these groups bind on the active sites of bacterial enzymes, inactivating them.  

As a result, oregano oil has powerful antibacterial properties, and is even effective against antibiotic-resistant strains of bacteria such as methicillin-resistant Staphylococcus aureus, as demonstrated by numerous studies. 

What is the action of oil of oregano on good bacteria?

The effect of oregano oil on good bacteria is of favoring their growth and their adhesion on the intestine walls (1).

Probiotic bacteria are favored by the presence of plant antioxidants, such as organic acids and phenolics and also by some minerals provided by plant extracts and oils. Phenolics are antioxidants, that means, they can reduce the oxygen concentration in the intestines.

Since probiotics are preferentially anaerobic (they grow better without oxygen), their growth is favored by the lower oxygen concentration. Probiotic bacteria also produce organic acids and other compounds, which are known to be antioxidant and improve health (1,6).

What are other benefits of oregano oil?

The other benefits of oregano oil are improving health by the preventive action against metabolic diseases, such as diabetes, obesity and heart disease (3).

Research investigating the possible health benefits of oregano oil has confirmed that oregano oil 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 aroma. 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

How much oil of oregano should you take?

There is not much information available regarding the use of oregano oil and its potential toxicity doses for humans, since most of the studies were realized in animal models. In this way, it is recommended to be used carefully and with moderation, especially in the case of children and pregnant women (4).

Is there any risk of using oregano oil?

Yes, there are risks related to the use of great amounts of oregano oil, as well as in small amounts, in the case of allergic reactions. Essential oils are related to possible allergic reactions and intoxications.

It is recommended to consult a doctor before using oregano oil or any plant oil directly or as a supplement form (5). 


In this brief article we answered the question, “does oil of oregano kill good bacteria?” and discussed how oregano oil kills bacteria, as well as other effects of the oil of oregano. 


  1. Gyawali, Rabin, and Salam A. Ibrahim. Impact of plant derivatives on the growth of foodborne pathogens and the functionality of probiotics. Appl Microbiol Biotechnol, 2012, 95, 29-45.
  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.