A steam-distilled essential oil from oregano leaf, sold neat, diluted in a carrier oil, or as an emulsified softgel. Its dominant compounds are the phenolic monoterpenes carvacrol and thymol.
Almost everything written about oregano oil rests on laboratory work: carvacrol disrupts bacterial and fungal membranes in a dish at concentrations that are easy to reach in vitro and much harder to reach in a human gut. Controlled human trials are close to non-existent, and the products vary enormously — "oregano oil" on a label may be Origanum vulgare, Origanum onites or Thymus capitatus, at anything from 3% to 85% carvacrol.
Usually expressed as percentage carvacrol; retail products commonly claim 55–85% — a product without this marker may not resemble what was studied.
Also known as
Oil of oregano, Origanum oil, Wild oregano oil
Regulation: Sold in the US as a dietary supplement, which means it reaches shelves without any pre-market review of efficacy or safety. Undiluted essential oil is not intended for internal use by most manufacturers, and dilution instructions vary widely between brands.
What the research used
The amounts, forms and durations published trials of Oregano oil actually administered.
These are the amounts published trials administered — not a recommendation, and not a dose to copy. Trial participants were screened, supervised and given a characterised preparation. What is in a retail bottle is frequently not what was studied, and the amount that suits one person is not general advice.
Studied for Intestinal parasite carriage
600 mg
Not enough
Emulsified oregano oil, divided doses · 6 weeks
From a single small open-label study with no control group. It is the most-cited human dose for oregano oil and it is nowhere near enough to establish a dose.
Studied for General supplement use
50–200 mg
Not enough
Softgel of oil in a carrier · Typically labelled 55–75% carvacrol
This is what retail products contain, not what trials tested. There is no established human dose for oregano oil, and carvacrol content between brands can differ several-fold.
This is general information about food, not medical advice. It cannot diagnose, treat or replace guidance from a clinician who knows your history.
When it was taken
Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.
None of the timings below were directly compared in a trial. They reflect how the research happened to dose, or what the pharmacology implies — which is not the same as a timing being better.
🍽️With food
Not enough
Usually taken with a meal because neat phenolic oils are irritating to an empty stomach. That is tolerability reasoning, not a tested comparison.
Timing was not directly compared. This reflects convention or how the compound behaves in the body, not a trial showing this window works better.
The evidence in depth
Best supported: Not enough
What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how promising the supplement sounds. How we rate evidence.
Evidence is limited for oregano oil and digestive symptoms. It is widely sold for small intestinal bacterial overgrowth and gut yeast on the strength of laboratory antimicrobial work; controlled human trials measuring symptoms are essentially absent.
What may be going on: Carvacrol and thymol disrupt microbial cell membranes in vitro. Whether enough intact carvacrol survives digestion to do that in the small intestine has not been established in people.
Not enough evidence. Not enough human research to say anything useful yet.
There is not enough human research to say whether oregano oil affects respiratory infections. The antimicrobial data are almost entirely from cell culture and animal work.
Not enough evidence. Not enough human research to say anything useful yet.
No source is attached to this association yet, so it is rated not enough evidenceby default. It is listed because people commonly ask about it — not because there is evidence for it.
Things to know
Interactions, contraindications and dose limits, most serious first. Concentrated extracts interact with medication in ways the whole plant does not, so this section carries more weight here than it does on a food page.
Worth knowing
Undiluted essential oil is caustic
Neat oregano oil burns mucous membranes. Reports of mouth, throat and oesophageal irritation follow swallowing it undiluted, and it should never go on skin or in a mouth without carrier dilution.
Avoid
Not established as safe in pregnancy
Concentrated oregano preparations have traditionally been used as emmenagogues, and animal work raises questions about high-dose exposure. Culinary amounts are a different matter from concentrated oil, which is best avoided in pregnancy and while breastfeeding.
Interaction
Possible additive effect with blood thinners
Interacts withWarfarin, direct oral anticoagulants, antiplatelet drugs
Carvacrol and thymol inhibit platelet aggregation in laboratory work, and oregano leaf carries vitamin K. Human interaction data are absent, so anyone on warfarin or a direct oral anticoagulant should raise it with their prescriber rather than assume it is inert.
Worth knowing
Blood sugar and iron absorption
Small studies suggest oregano preparations may lower blood glucose modestly and reduce non-heme iron absorption from a meal. Neither is well characterised, but both matter for people on glucose-lowering medication or managing low iron.
Allergy
Lamiaceae cross-reactivity
People who react to basil, mint, sage, thyme or lavender may react to oregano oil, which belongs to the same plant family.
In the food catalogue
The whole-food form, where one exists. The evidence for a concentrated extract rarely transfers to the food, or the other way round — these are cross-links, not equivalents.