If you’ve spent any time searching for natural antimicrobial supplements, you’ve likely come across oregano oil. It’s been called “nature’s strongest antibiotic” by enthusiastic proponents, though that claim deserves some scrutiny. What’s actually true is that oregano oil contains compounds with genuine antimicrobial properties that have been studied in laboratory and, to a lesser extent, in human trials.

Oregano oil (sometimes marketed as “Oil of Oregano”) is extracted from the leaves of the oregano plant through steam distillation. Don’t confuse this with the oregano you sprinkle on pizza - the concentrated essential oil is far more potent and isn’t used for cooking. Instead, it’s taken as a supplement or applied topically (always diluted) for various health purposes.

What Is Oregano Oil and Where Does It Come From?

Oregano (Origanum vulgare) is a perennial herb native to the Mediterranean region, though it now grows across Europe, North Africa, and parts of Asia. The plant thrives at elevations between 500 and 3,600 metres and belongs to the Lamiaceae (mint) family, which includes other aromatic herbs like thyme, rosemary, and lavender.

The essential oil extracted from oregano leaves contains several active compounds. The two most important are:

Carvacrol - This phenolic compound typically makes up 60-80% of high-quality oregano oil and is responsible for most of its antimicrobial activity. Studies have demonstrated carvacrol’s effects against various bacteria, fungi, and even some viruses in laboratory settings.

Thymol - Also found in thyme, this compound contributes additional antimicrobial properties and works synergistically with carvacrol.

Other components include cymene, terpinene, and various sesquiterpenes, though these are present in smaller amounts.

Traditionally, oregano has been used in folk medicine across Mediterranean cultures for respiratory complaints, digestive issues, and general infections. Modern research has begun investigating whether these traditional uses have scientific merit.

What Are the Benefits of Oregano Oil?

1. Antibacterial Effects

Infectious diseases caused by harmful bacteria remain a significant global health challenge. The rise of antibiotic-resistant strains has sparked interest in natural antimicrobial compounds, including those found in oregano oil.

Laboratory studies have shown oregano oil has activity against numerous bacterial strains, including Pseudomonas aeruginosa (a bacterium that causes urinary tract infections, respiratory infections, and skin infections), Staphylococcus aureus (including some antibiotic-resistant strains), and Escherichia coli.

One animal study demonstrated that oral oregano oil helped fight Staphylococcus aureus infections in mice [1]. The researchers found reduced bacterial counts and improved survival rates compared to untreated controls.

My take: The laboratory evidence for oregano oil’s antibacterial properties is reasonably solid. However, killing bacteria in a petri dish is very different from treating an infection in a human body. We need more clinical trials to determine effective doses, appropriate uses, and whether oregano oil can actually help with bacterial infections in people. I wouldn’t recommend it as a substitute for antibiotics when you have a genuine infection.

2. Anti-Inflammatory and Antioxidant Activity

Chronic inflammation contributes to numerous health problems, including cardiovascular disease, diabetes, and certain cancers. Antioxidants help neutralise free radicals that can damage cells and promote inflammation.

A systematic review and meta-analysis of nine animal studies examined carvacrol’s anti-inflammatory effects [2]. The researchers found that carvacrol reduced several inflammatory markers, including interleukin-1β, interleukin-4, interleukin-8, and malondialdehyde. Interestingly, it didn’t significantly affect interleukin-6 or tumour necrosis factor-alpha (TNF-α), two other key inflammatory markers.

Worth noting: These are animal studies, not human trials. While the anti-inflammatory effects look promising, we don’t yet know whether supplementing with oregano oil produces meaningful anti-inflammatory benefits in people. The doses used in animal research often don’t translate directly to human supplementation.

3. Wound Healing Support

Wound healing involves four distinct phases: haemostasis (stopping bleeding), inflammation, proliferation (new tissue growth), and remodelling. Various factors can disrupt this process, including infection, diabetes, and poor circulation.

A systematic review examining 13 animal experiments found that thymol and carvacrol (the main components of oregano oil) positively influenced multiple stages of wound healing [3]. These compounds appeared to regulate inflammatory responses, promote new tissue development, encourage blood vessel formation, and improve collagen deposition.

The catch: All this evidence comes from animal studies, mostly involving rats and mice. Topical application of diluted oregano oil or thymol-containing preparations might theoretically help minor wounds, but there’s no robust human evidence to support this. Plus, undiluted oregano oil can actually damage skin and delay healing, so proper dilution is essential.

4. Possible Benefits for Asthma

Asthma affects over 300 million people worldwide and causes approximately 250,000 deaths annually. Current treatment relies primarily on inhaled corticosteroids, which are effective but can have side effects with long-term use.

One small clinical trial tested carvacrol capsules in 23 patients with moderate to severe asthma over two months [4]. The researchers reported improvements in lung function tests, respiratory symptoms, and inflammatory markers (including high-sensitivity C-reactive protein).

Reality check: This is a single small trial with just 23 participants. While the results are intriguing, the study size is far too small to draw firm conclusions. Asthma is a serious condition that requires proper medical management - I wouldn’t suggest anyone replace their inhaler with oregano oil based on this limited evidence.

5. Activity Against Intestinal Parasites

Parasitic infections remain common in developing countries where clean water and sanitation are limited. These infections can cause digestive problems, malnutrition, and developmental issues in children.

A small human trial gave oregano oil to 14 adults who tested positive for intestinal parasites (specifically Blastocystis hominis) for six weeks [5]. Most participants showed improvement in their symptoms and reduced parasite burden.

My assessment: Fourteen people is a tiny study, and there was no control group taking a placebo. The results are suggestive but far from conclusive. If you suspect a parasitic infection, you need proper medical testing and treatment, not essential oil supplements.

Additional Traditional Uses

Beyond the benefits with some scientific backing, oregano oil has been traditionally used for:

Respiratory conditions: Inhaling diluted oregano oil steam is a folk remedy for coughs and congestion. Some people find it soothing, though there’s no clinical evidence proving it speeds recovery from colds or flu.
Oral health: The antimicrobial properties have led to oregano oil being included in some natural mouthwashes. A few small studies suggest it may help reduce oral bacteria, but more research is needed.
Skin conditions: Diluted oregano oil has been applied to fungal infections like athlete’s foot and nail fungus. Laboratory studies show antifungal activity, but clinical trials in humans are limited.

What Are the Side Effects of Oregano Oil?

When used in moderate amounts for short periods, oregano oil is generally well tolerated by healthy adults. However, possible side effects include:

Gastrointestinal upset: Nausea, vomiting, diarrhoea, and stomach discomfort are the most commonly reported side effects when taking oregano oil orally.
Allergic reactions: People allergic to plants in the Lamiaceae family may react to oregano oil. This includes those allergic to basil, mint, sage, rosemary, thyme, or lavender.
Skin irritation: Undiluted oregano oil can cause burns, irritation, and rashes when applied to skin. Always dilute with a carrier oil (like olive or coconut oil) before topical use.
Other reported effects: Headache, dizziness, fatigue, muscle pain, and difficulty swallowing have been occasionally reported.

Safety Precautions and Contraindications

Before using oregano oil, be aware of these important safety considerations:

1. Allergies to Lamiaceae plants: If you’ve had allergic reactions to basil, peppermint, rosemary, sage, marjoram, thyme, lavender, or perilla, you should avoid oregano oil. The same allergenic compounds may be present.

2. Pregnancy and breastfeeding: There’s insufficient safety data for pregnant or nursing women. Given that oregano oil may have effects on hormone levels and uterine contractions, it’s best avoided during pregnancy.

3. Children and infants: The concentrated essential oil hasn’t been studied for safety in children. Keep oregano oil products away from young children.

4. Liver or kidney problems: Since the body must process and eliminate the compounds in oregano oil, those with compromised liver or kidney function should avoid it.

5. Bleeding disorders or blood-thinning medications: Oregano oil may have anticoagulant effects. Avoid it if you have bleeding disorders, are taking blood thinners like warfarin, aspirin, clopidogrel, or dabigatran, or are scheduled for surgery within two weeks.

6. Other herbs affecting coagulation: Don’t combine oregano oil with supplements that may also thin blood, such as angelica, garlic, ginger, ginkgo, turmeric, or horse chestnut.

7. Topical use precautions: Never apply undiluted oregano oil to skin. Mix a few drops with a carrier oil (olive, coconut, or jojoba) at a ratio of approximately 1:10 to avoid chemical burns.

8. Diabetes medications: Oregano oil may lower blood sugar, which could interact with diabetes medications like metformin, insulin, or sulfonylureas. Monitor blood sugar closely if you choose to use it.

9. Blood sugar-lowering supplements: Avoid combining with other supplements that affect blood sugar, including bitter melon, fenugreek, chromium, or alpha-lipoic acid.

10. Lithium and diuretics: Oregano oil may affect how the body processes lithium and could interact with diuretic medications. Consult your doctor if you take these medications.

Dosage Considerations

There’s no established standardised dose for oregano oil because clinical trials are limited and have used varying preparations. However, here are some general guidelines from available research:

Oral supplements: Most commercial products provide 100-200mg of oregano oil per capsule, often standardised to contain a minimum percentage of carvacrol. Following product label instructions is advisable.
Liquid oil: Some practitioners suggest 2-4 drops diluted in water or juice, but this is based on traditional use rather than clinical evidence.
Topical application: Dilute 1-2 drops of essential oil in approximately 10ml of carrier oil before applying to skin.
Duration: Most sources recommend limiting oral use to 2-4 weeks at a time to reduce the risk of disrupting gut bacteria. Like antibiotics, oregano oil may affect beneficial gut microbiota along with harmful organisms.

How to Use Oregano at Home

If you’d prefer gentler approaches, you can enjoy oregano’s potential benefits through culinary uses:

Oregano Tea

Oregano tea provides a milder way to consume the herb’s beneficial compounds.

To make oregano tea:

Strip fresh oregano leaves from the stem and chop them finely to release more of the active compounds.
Place about one tablespoon of fresh herbs (or one teaspoon dried) in a cup.
Pour boiling water over the leaves.
Let it steep for 15-20 minutes, then strain.
Drink warm, with honey if desired.

You can also make a larger batch by adding a cup of fresh oregano to a glass jar, covering with four cups of boiling water, and letting it cool before refrigerating. This keeps for about a week.

Oregano tea is much gentler than concentrated oil and is a traditional remedy for digestive discomfort and respiratory congestion. However, don’t expect the same antimicrobial potency as the essential oil.

Oregano Seasoning

Simply adding more oregano to your cooking provides flavonoids and antioxidants in safe, food-level amounts. Dried oregano works well in:

Pasta sauces and pizza
Mediterranean vegetable dishes
Marinades for meat and fish
Homemade salad dressings

Comparing Oregano Oil to Other Essential Oils

If you’re interested in antimicrobial essential oils, oregano is often compared to tea tree oil. Both have demonstrated activity against bacteria and fungi in laboratory studies. Tea tree oil has somewhat more clinical research supporting topical uses (particularly for acne and minor skin infections), while oregano oil’s carvacrol content makes it potentially more potent but also more likely to cause skin irritation.

The Bottom Line

Oregano oil contains compounds with genuine antimicrobial and anti-inflammatory properties demonstrated in laboratory and animal studies. A handful of small human trials hint at potential benefits for conditions like intestinal parasites and asthma, but the evidence is preliminary.

What we can say with reasonable confidence:

Oregano oil has antimicrobial activity in laboratory settings
The main active components are carvacrol and thymol
It should always be diluted before topical use
It’s probably safe for short-term use in healthy adults at typical supplement doses
It has significant drug interactions, particularly with blood thinners and diabetes medications

What remains uncertain:

Whether oral supplementation actually fights infections in humans
Optimal dosing for any specific condition
Long-term safety
Whether it’s more effective than cheaper alternatives like garlic or honey

If you’re considering oregano oil, start with small amounts, watch for adverse reactions, and don’t use it as a substitute for medical treatment of serious infections. As with any supplement, tell your doctor what you’re taking, especially if you have health conditions or take medications.

References

Manohar V, et al. Antifungal activities of origanum oil against Candida albicans. Mol Cell Biochem. 2001;228(1-2):111-7.
Gholijani N, et al. Modulatory effects of carvacrol on pro-inflammatory cytokines in animal models: A systematic review and meta-analysis. Immunopharmacol Immunotoxicol. 2020;42(3):228-237.
Niksic H, et al. Thymol and carvacrol wound healing effects: A systematic review. Chem Biol Interact. 2019;298:59-68.
Alavinezhad A, et al. Effect of carvacrol on bronchial responsiveness, inflammatory mediators, and pulmonary function tests in asthmatic patients: A randomized, double-blind, placebo-controlled, phase II clinical trial. Phytother Res. 2018;32(1):151-159.
Force M, et al. Inhibition of enteric parasites by emulsified oil of oregano in vivo. Phytother Res. 2000;14(3):213-4.
Singletary K. Oregano: Overview of the Literature on Health Benefits. Nutr Today. 2010;45(3):129-138.