Home Ingredients Carvacrol (Oregano Oil Phenol)

Carvacrol (Oregano Oil Phenol)

Evidence Level
Limited
6 Clinical Trials
5 Documented Benefits
2/5 Evidence Score

Carvacrol is a phenol found in the essential oils of oregano and thyme, and it is usually the main compound in the oregano oil capsules sold as supplements. This page covers the single compound; whole oregano oil, which also contains thymol and other constituents, has its own page. The human research on oral carvacrol comes from one research group in Iran: a short safety study in healthy adults and five small placebo-controlled reports in patients with asthma or with old chemical-weapon lung injury, in which inflammation and oxidative stress markers improved over two months. Most results were measured against each group's own starting values, and none has been repeated elsewhere. The well-known antibacterial and antifungal effects of carvacrol come from laboratory cultures, not from studies in people. Concentrated carvacrol irritates the mouth, and pregnancy safety has not been studied.

Studied Dose 1.2 mg/kg/day in capsules for two months in the patient trials (about 84 mg/day for a 70 kg adult); 1 or 2 mg/kg/day for one month in the healthy volunteer safety study. No dose has been established for supplement use.
Active Compound Carvacrol (5-isopropyl-2-methylphenol), a monoterpene phenol from the essential oils of oregano, thyme and related Lamiaceae plants.

Benefits

CRP and cytokine levels in small trials

In two-month trials of 1.2 mg/kg/day carvacrol capsules, hs-CRP fell in adults with asthma, and TNF-alpha and several interleukins fell in people with decades-old sulfur mustard lung injury, all against each group's own baseline. No trial abstract reports a carvacrol versus placebo difference in CRP or cytokines; one 20-person trial did so for white cell counts. One team ran every trial, and two reports may share participants.

Supported by Trial 1, Trial 4

Antioxidant enzyme and oxidative stress markers in two carvacrol trials

In 20 patients with old sulfur mustard lung injury, two months of carvacrol raised thiol, superoxide dismutase and catalase and lowered malondialdehyde, and these were better than placebo at the end. An asthma trial from the same team reported improvement in most oxidative stress markers against baseline. Both trials were small and in patients.

Supported by Trial 3, Trial 2

Breathing test measures in patients taking carvacrol capsules

Pulmonary function values and respiratory symptom scores improved over two months on carvacrol in the asthma and sulfur mustard trials, mostly measured against baseline, alongside usual medicines. These are small studies in people with diagnosed lung disease, and carvacrol is not a replacement for prescribed treatment.

Supported by Trial 2, Trial 1

Tolerance at 1 to 2 mg/kg/day for one month in healthy adults

In a phase I study, healthy adults took 1 or 2 mg/kg/day of carvacrol for a month. Some blood values shifted, such as lower hemoglobin and longer prothrombin time at the lower dose and lower HDL cholesterol and iron at the higher dose, but all stayed within the normal range. Longer use has not been studied.

Supported by Trial 6

Antibacterial activity of carvacrol in laboratory cultures

In culture, carvacrol makes bacterial membranes leak ions and kills Bacillus cereus, and it reduced spore production by Clostridium difficile. Bacteria grown with low carvacrol levels also adapted to it. These are test tube findings; no human study shows that swallowing carvacrol prevents or treats any infection.

Supported by Trial 2, Trial 3

Mechanism of action

1

Leaky bacterial membranes (laboratory)

Carvacrol lodges in bacterial membranes and makes them permeable to protons and potassium, collapsing the membrane potential and draining the cell's ATP, which leads to cell death in culture. Bacteria exposed to sub-lethal amounts can change their membrane fats and become less sensitive. Shown in the lab only.

2

Warmth and irritation receptor activation (TRPV3)

Carvacrol activates TRPV3, a warmth-sensing ion channel. On the human tongue it causes numbing, warmth and brief burning or stinging that fades with repeated exposure, which helps explain why concentrated oregano oil feels hot and irritating in the mouth.

3

Rapid conjugation and liver metabolism

In chickens fed a delayed-release carvacrol product designed to reach the lower gut, very little free carvacrol reached the blood; most circulated as glucuronide and sulfate conjugates and much of the dose passed to the lower gut. In human liver microsomes, the enzyme CYP2A6 did most of the metabolism. How much free carvacrol reaches human tissues after a capsule is not known.

Clinical trials

1
Carvacrol Capsules in Adults with Asthma: Phase II Placebo-Controlled Trial
PubMed

Randomized, double blind, placebo controlled phase II trial of carvacrol capsules 1.2 mg/kg/day for two months. (Alavinezhad et al. 2018, Phytother Res)

23 adults with asthma (12 carvacrol, 11 placebo) in Mashhad, Iran.

Pulmonary function values rose and most respiratory symptoms, white cell counts and hs-CRP fell in the carvacrol group after two months, with no significant changes on placebo. The abstract reports changes against each group's baseline, not a direct comparison between groups. Purified carvacrol, not oregano oil.

2
Carvacrol in Moderate Asthma: Oxidative Stress and Cytokine Trial
PubMed

Randomized, placebo controlled, double blind trial of carvacrol 1.2 mg/kg/day, capsules three times daily with usual medicines, for two months. (Ghorani et al. 2021, Phytomedicine)

33 adults with moderate asthma (17 carvacrol, 16 placebo).

Respiratory symptoms, pulmonary function, most oxidative stress markers and serum and blood cell cytokine levels improved against pretreatment values in the carvacrol group; the placebo group showed no significant changes. The abstract reports no direct comparison between groups. Same research team as the other carvacrol trials, with no independent replication.

3
Carvacrol After Sulfur Mustard Lung Injury: Blood Cells and Antioxidant Markers
PubMed

Randomized, double blind trial of carvacrol 1.2 mg/kg/day or placebo for two months. (Khazdair et al. 2018, J Clin Pharm Ther)

20 patients exposed to sulfur mustard 27 to 30 years earlier (10 per group).

White cells and neutrophils fell, thiol, superoxide dismutase and catalase rose and malondialdehyde fell in the carvacrol group; after two months these markers and FVC and PEF were significantly better than placebo. Ten people per group.

4
Carvacrol After Sulfur Mustard Lung Injury: Serum Cytokines
PubMed

Double blind, randomized, placebo controlled trial of carvacrol 1.2 mg/kg/day for two months. (Khazdair et al. 2019, Cytokine)

20 patients exposed to sulfur mustard 27 to 30 years earlier (10 per group); possibly the same participants as the 2018 report.

In the carvacrol group, IL-2, IL-4, IL-6 and IL-8 fell and IL-10 and interferon gamma rose against baseline, and several airflow measures rose. The abstract reports within-group changes only.

5
Carvacrol in Veterans Exposed to Sulfur Mustard: Inflammatory Mediators
PubMed

Randomized, placebo controlled trial (IRCT2014031617020N1) of carvacrol 1.2 mg/kg/day for two months. (Khazdair et al. 2019, Respir Med)

21 veterans exposed to sulfur mustard more than two decades earlier.

FEV1 rose, chest and night wheeze and night cough fell, and serum TNF-alpha, EGF, VEGF and (at two months) MCP-1 fell in the carvacrol group, all against baseline. The abstract gives neither group sizes nor any between-group comparison.

6
Carvacrol Safety in Healthy Adults: Phase I Study
PubMed

Randomized phase I safety and tolerability study of oral carvacrol at 1 or 2 mg/kg/day for one month. (Ghorani et al. 2021, Drug Chem Toxicol)

Healthy adults in two dose groups; the abstract does not state the number.

Several blood values changed from baseline, including lower hemoglobin and hematocrit and higher prothrombin time and triglycerides at 1 mg/kg/day, and lower HDL cholesterol, iron and red cell count at 2 mg/kg/day, but all post treatment values were within the normal range. FEV1 rose at 2 mg/kg/day. The authors judged carvacrol safe and tolerated at these doses over one month.

Side effects and drug interactions

Common Potential side effects

Mouth and throat irritation: carvacrol applied to the tongue caused numbing, warmth and brief burning or stinging in a human sensory study, so concentrated carvacrol and oregano oil should not be held in the mouth or taken undiluted.
Blood test shifts: in a one-month study in healthy adults, carvacrol at 1 to 2 mg/kg/day changed some blood values (for example hemoglobin, iron, HDL cholesterol and prothrombin time) while keeping them in the normal range. Effects of longer use are unknown.
High doses: in rats, carvacrol at 100 and 500 mg/kg raised the pancreatic enzyme alpha-amylase and caused inflammatory cell infiltration and swelling in the pancreas, while 10 mg/kg did not. Even allowing for body size, these doses are far above the amounts tested in people, but they show that toxicity rises with dose.
Pregnancy and breastfeeding: no human safety data exist. In lab tissue from pregnant rats, carvacrol inhibited uterine muscle contractions, so it should be avoided in concentrated form during pregnancy unless a doctor advises otherwise.
Children: all human studies were in adults; carvacrol supplements have not been studied in children.

Important Drug interactions

Anticoagulants (warfarin, acenocoumarol): in a single case report, a woman on acenocoumarol had a sharply raised INR after a week of daily oregano tea, and prothrombin time rose, though within the normal range, in a carvacrol safety study. Anyone on a blood thinner should talk to their doctor and have INR checked before using carvacrol or oregano oil.
Drugs cleared by CYP2A6: in human liver microsomes, CYP2A6 was the main enzyme that metabolized carvacrol, so competition with other CYP2A6 substrates is possible; this has not been tested in people.
Drugs cleared by UGT1A9, such as the anesthetic propofol: carvacrol inhibited UGT1A9 in laboratory enzyme tests. The clinical relevance is unknown; mention supplement use before surgery or sedation.

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Frequently asked questions about Carvacrol (Oregano Oil Phenol)

Is carvacrol the same as oregano oil?

No. Carvacrol is one compound, usually the largest one, in oregano essential oil, which also contains thymol and other constituents in amounts that vary between plants and harvests. Most human research on oral use tested purified carvacrol capsules, not oregano oil.

Has carvacrol been tested in people?

Yes, but only in small studies from one research team: a one-month safety study in healthy adults and two-month placebo-controlled trials in 20 to 33 patients with asthma or old chemical-weapon lung injury, which reported lower inflammation and oxidative stress markers, mostly measured against each group's own starting values. These results have not been repeated by other groups.

Does carvacrol kill germs inside the body?

That has not been shown. Carvacrol kills bacteria in laboratory dishes by damaging their membranes, and in chickens it lowered gut bacteria counts, but very little free carvacrol reached the birds' blood. No human study shows that carvacrol supplements prevent or treat an infection, and they are not a substitute for prescribed antibiotics.

Is carvacrol safe, and does it have side effects?

One month at 1 to 2 mg/kg/day was tolerated by healthy adults, with blood values staying in the normal range. Concentrated carvacrol irritates the mouth, high doses damaged the pancreas in rats, pregnancy safety is unknown, and it may affect blood thinners, so talk to a doctor if you take medicines.

What is Carvacrol?

Carvacrol is a phenol found in the essential oils of oregano and thyme, and it is usually the main compound in the oregano oil capsules sold as supplements. This page covers the single compound; whole oregano oil, which also contains thymol and other constituents, has its own page.

What is Carvacrol used for?

NutraSmarts does not list Carvacrol under a health category. What the research covers: In two-month trials of 1.2 mg/kg/day carvacrol capsules, hs-CRP fell in adults with asthma, and TNF-alpha and several interleukins fell in people with decades-old sulfur mustard lung injury, all against each group's own baseline.

What is the recommended dosage of Carvacrol?

The clinically studied dose is 1.2 mg/kg/day in capsules for two months in the patient trials (about 84 mg/day for a 70 kg adult); 1 or 2 mg/kg/day for one month in the healthy volunteer safety study. No dose has been established for supplement use. Always follow the product label and check with a healthcare provider for personal advice.

Does Carvacrol interact with any medications?

Possible interactions include: Anticoagulants (warfarin, acenocoumarol): in a single case report, a woman on acenocoumarol had a sharply raised INR after a week of daily oregano tea, and prothrombin time rose, though within the normal range, in a carvacrol safety study. If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for Carvacrol?

NutraSmarts rates the evidence for Carvacrol as Limited (2 out of 5). It is backed by 6 study summaries and 16 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(16 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Alavinezhad A, Khazdair MR, Boskabady MH. Possible therapeutic effect of carvacrol on asthmatic patients: A randomized, double blind, placebo-controlled, Phase II clinical trial. Phytother Res. 2018;32(1):151-159. doi: 10.1002/ptr.5967.PubMedUsed to support: Randomized double blind placebo controlled phase II trial in 23 adults with asthma: 12 took carvacrol capsules at 1.2 mg/kg/day and 11 took placebo for two months. In the carvacrol group, pulmonary function values rose, most respiratory symptoms fell, and total and differential white cell counts and hs-CRP fell; the placebo group showed no significant changes. The abstract reports changes against each group's baseline, not a direct comparison between groups. Purified carvacrol, one research group, patients with a diagnosed lung disease.
  2. Ghorani V, Alavinezhad A, Rajabi O, Boskabady MH. Carvacrol improves pulmonary function tests, oxidant/antioxidant parameters and cytokine levels in asthmatic patients: A randomized, double-blind, clinical trial. Phytomedicine. 2021;85:153539. doi: 10.1016/j.phymed.2021.153539.PubMedUsed to support: Randomized placebo controlled double blind trial in 33 adults with moderate asthma (17 carvacrol at 1.2 mg/kg/day, 16 placebo), capsules taken three times a day for two months alongside usual medicines. Respiratory symptoms, pulmonary function, most oxidative stress markers and serum and blood cell cytokine levels improved against pretreatment values in the carvacrol group, with no significant change on placebo. Same research group as the other carvacrol trials.
  3. Khazdair MR, Alavinezhad A, Boskabady MH. Carvacrol ameliorates haematological parameters, oxidant/antioxidant biomarkers and pulmonary function tests in patients with sulphur mustard-induced lung disorders: A randomized double-blind clinical trial. J Clin Pharm Ther. 2018;43(5):664-674. doi: 10.1111/jcpt.12684.PubMedUsed to support: Randomized double blind trial in 20 patients exposed to sulfur mustard 27 to 30 years earlier (10 carvacrol at 1.2 mg/kg/day, 10 placebo) for two months. Total white cells and neutrophils fell, thiol, superoxide dismutase and catalase rose and malondialdehyde fell in the carvacrol group, and the abstract reports these and FVC and PEF as significantly better than placebo after two months. One of the few between-group results in this set of trials.
  4. Khazdair MR, Boskabady MH. A double-blind, randomized, placebo-controlled clinical trial on the effect of carvacrol on serum cytokine levels and pulmonary function tests in sulfur mustard induced lung injury. Cytokine. 2019;113:311-318. doi: 10.1016/j.cyto.2018.07.031.PubMedUsed to support: Randomized double blind placebo controlled trial in 20 patients exposed to sulfur mustard 27 to 30 years earlier (10 per group), carvacrol 1.2 mg/kg/day for two months. In the carvacrol group, serum IL-2, IL-4, IL-6 and IL-8 fell and IL-10 and interferon gamma rose against baseline, and some airflow measures rose. Results are reported as within-group changes. The group sizes and exposure history match the other sulfur mustard paper from the same team, so the two reports may describe overlapping participants.
  5. Khazdair MR, Boskabady MH. The effect of carvacrol on inflammatory mediators and respiratory symptoms in veterans exposed to sulfur mustard, a randomized, placebo-controlled trial. Respir Med. 2019;150:21-29. doi: 10.1016/j.rmed.2019.01.020.PubMedUsed to support: Randomized placebo controlled trial (registered IRCT2014031617020N1) in 21 veterans exposed to sulfur mustard more than two decades earlier, carvacrol 1.2 mg/kg/day or placebo for two months. In the carvacrol group, FEV1 rose, wheeze and night cough fell, serum TNF-alpha, EGF and VEGF fell at one and two months and MCP-1 at two months, all reported against baseline.
  6. Ghorani V, Alavinezhad A, Rajabi O, Mohammadpour AH, Boskabady MH. Safety and tolerability of carvacrol in healthy subjects: a phase I clinical study. Drug Chem Toxicol. 2021;44(2):177-189. doi: 10.1080/01480545.2018.1538233.PubMedUsed to support: Phase I study in healthy adults randomly assigned to oral carvacrol at 1 or 2 mg/kg/day for one month, with blood and urine tests and spirometry before and after. Several values shifted from baseline (for example hemoglobin and hematocrit fell and prothrombin time and triglycerides rose at 1 mg/kg/day; HDL cholesterol, iron and red cell count fell at 2 mg/kg/day), but all post treatment values stayed within the normal range and the authors concluded carvacrol was tolerated. The abstract does not give the number of participants.
  7. Klein AH, Carstens MI, Carstens E. Eugenol and carvacrol induce temporally desensitizing patterns of oral irritation and enhance innocuous warmth and noxious heat sensation on the tongue. Pain. 2013;154(10):2078-2087. doi: 10.1016/j.pain.2013.06.025.PubMedUsed to support: Human sensory study (university volunteers; full text reports 524 subjects across all experiments) in which carvacrol solution (50 mM) was applied to one side of the tongue on filter paper. Carvacrol caused irritation that faded with repeated application, briefly enhanced heat pain and enhanced warmth; subjects described it mainly as numbing and warmth with brief burning, stinging and tingle. The paper describes carvacrol as an agonist of the warmth-sensing TRPV3 channel. This is a mouth sensation study, not a supplement trial.
  8. Dong RH, Fang ZZ, Zhu LL, Ge GB, Cao YF, Li XB, Hu CM, Yang L, Liu ZY. Identification of CYP isoforms involved in the metabolism of thymol and carvacrol in human liver microsomes (HLMs). Pharmazie. 2012;67(12):1002-6..PubMedUsed to support: Laboratory study with human liver microsomes and recombinant enzymes: carvacrol formed two metabolites, and CYP2A6 was the main enzyme responsible. The authors advise attention when carvacrol is combined with other compounds mainly cleared by CYP2A6. Test tube work, not a human interaction study.
  9. Dong RH, Fang ZZ, Zhu LL, Liang SC, Ge GB, Yang L, Liu ZY. Investigation of UDP-glucuronosyltransferases (UGTs) inhibitory properties of carvacrol. Phytother Res. 2012;26(1):86-90. doi: 10.1002/ptr.3525.PubMedUsed to support: Laboratory study with recombinant enzymes: carvacrol inhibited the drug metabolizing enzyme UGT1A9 (Ki 5.7 µM with one probe substrate and 25.0 µM with propofol) with negligible effects on other UGT forms. The authors caution that the results are substrate dependent and hard to extrapolate to people.
  10. Allaoua M, Etienne P, Noirot V, Carayon JL, Téné N, Bonnafé E, Treilhou M. Pharmacokinetic and antimicrobial activity of a new carvacrol-based product against a human pathogen, Campylobacter jejuni. J Appl Microbiol. 2018;125(4):1162-1174. doi: 10.1111/jam.13915.PubMedUsed to support: Laboratory and broiler chicken study of a delayed release carvacrol feed product. In the birds, carvacrol was found mainly in the ceca, large intestine and droppings, with extremely low free carvacrol in blood plasma and larger amounts of its glucuronide and sulfate metabolites. At about 9.5 mg/kg body weight per day in feed it lowered cecal Campylobacter jejuni load by 1.5 log after 35 days. Animal work; no human data.
  11. Stojanović NM, Stevanović M, Randjelović P, Mitić K, Petrović V, Sokolović D, Mladenović B, Lalić J, Radulović NS. Low dose of carvacrol prevents rat pancreas tissue damage after L-arginine application, while higher doses cause pancreatic tissue impairment. Food Chem Toxicol. 2019;128:280-285. doi: 10.1016/j.fct.2019.04.010.PubMedUsed to support: Rat study: carvacrol at 100 and 500 mg/kg raised serum alpha-amylase and caused inflammatory cell infiltration and patchy edema in the pancreas, while 10 mg/kg reduced damage in a chemically induced pancreatic injury model. Shows dose dependent toxicity at high intakes in animals; not a human study.
  12. Mooyottu S, Flock G, Venkitanarayanan K. Carvacrol reduces Clostridium difficile sporulation and spore outgrowth in vitro. J Med Microbiol. 2017;66(8):1229-1234. doi: 10.1099/jmm.0.000515.PubMedUsed to support: Laboratory study in two hypervirulent Clostridium difficile isolates: a sub-inhibitory concentration of carvacrol reduced spore production and down-regulated sporulation genes, and the minimum inhibitory concentration blocked spore outgrowth, although neither concentration stopped spore germination. Bacteria in culture only; no animal or human data.
  13. Munoz-Perez VM, Ortiz MI, Gerardo-Munoz LS, Carino-Cortes R, Salas-Casas A. Tocolytic effect of the monoterpenic phenol isomer, carvacrol, on the pregnant rat uterus. Chin J Physiol. 2020;63(5):204-210. doi: 10.4103/CJP.CJP_56_20.PubMedUsed to support: Organ bath study of uterine tissue taken from rats at 16 to 18 days of pregnancy: carvacrol caused concentration dependent inhibition of spontaneous and drug or electrically induced contractions, linked to calcium channel blockade. It shows carvacrol acts on pregnant uterine muscle in the lab; it is not a human pregnancy safety study.
  14. Ultee A, Kets EP, Smid EJ. Mechanisms of action of carvacrol on the food-borne pathogen Bacillus cereus. Appl Environ Microbiol. 1999;65(10):4606-10. doi: 10.1128/AEM.65.10.4606-4610.1999.PubMedUsed to support: Laboratory study in Bacillus cereus: 1 to 3 mM carvacrol cut viable cell numbers within 30 minutes, 2 mM depleted the cells' internal ATP within 7 minutes, concentrations from 0.01 mM reduced and from 0.15 mM fully dissipated the membrane potential, and the membrane became more permeable to protons and potassium. The authors conclude carvacrol kills by making the bacterial membrane leak ions.
  15. Ultee A, Kets EP, Alberda M, Hoekstra FA, Smid EJ. Adaptation of the food-borne pathogen Bacillus cereus to carvacrol. Arch Microbiol. 2000;174(4):233-8. doi: 10.1007/s002030000199.PubMedUsed to support: Laboratory study: Bacillus cereus grown with non-lethal carvacrol concentrations became less sensitive to it, by changing the fatty acid and head group make-up of its membrane to lower membrane fluidity. Shows bacteria can adapt to carvacrol in culture.
  16. Beghriche I, Belhachem A, Hamidene I, Fendri AH. [Origanum vulgare and hemorrhagic risk, about a case]. Ann Cardiol Angeiol (Paris). 2025;74(1):101856. doi: 10.1016/j.ancard.2024.101856.PubMedUsed to support: Single case report (article in French, English abstract) of a 77 year old woman stable for years on the anticoagulant acenocoumarol whose INR rose to 6.42 after a week of daily oregano herbal tea, occasionally with verbena. The INR fell after the anticoagulant was paused for a day and the tea stopped and stabilized when intake was limited and the anticoagulant dose reduced. The authors attribute the effect partly to carvacrol and thymol. One case, tea rather than oil or purified carvacrol, and causation is not proven.