Oregano herb supplement review, dosage, use for immune system  health benefit and side effects
May 20 2018 by Ray Sahelian, M.D.

Oregano herb is a member of the mint family. It is light green in color with strong, aromatic odor and pleasantly bitter taste. This spice goes well with tomato sauces, pizza, and vegetable and fish salads.

Compounds in oregano herb
There are dozens, including thymol, sabinene hydrate, aristolochic acid, and carvacol.

Q. Can you tell me if oregano oil typically contains thymol, and if this causes liver toxicity. I bought 2 different brands of oregano oil and it just lists carvacrol as an ingredient, but not thymol.
   A. As far as I know, reasonable amounts of thymol contained in dietary supplements are not toxic to the liver.

Environ Toxicol Pharmacol. 2018. Hepatoprotective effect of thymol against subchronic toxicity of titanium dioxide nanoparticles: Biochemical and histological evidences. Thymol effectively protects against nano-TiO2-induced hepatotoxicity in rats by its antioxidant properties.

Molecules. 2017. Cytotoxic Activity of Origanum Vulgare on Hepatocellular Carcinoma cell Line HepG2 and Evaluation of its Biological Activity.

Res Pharm Sci. 2018. Effects of oregano essential oil on brain TLR4 and TLR2 gene expression and depressive-like behavior in a rat model. The compositions of the oregano oil were determined by gas chromatography-mass spectroscopy. The main constituents were thymol (20%), gamma-terpinene (9%), borneol (9%), cymene (7%), carvacrol (6%), alfa-terpinene (5%), and sabinene (5%). Administration significantly alleviated depressive symptoms.

Phytother Res. 2018. Carvacrol and human health: A comprehensive review. Carvacrol is a phenolic monoterpenoid found in essential oils of oregano (Origanum vulgare), thyme (Thymus vulgaris), pepperwort (Lepidium flavum), wild bergamot (Citrus aurantium bergamia), and other plants. Carvacrol possesses a wide range of bioactivities putatively useful for clinical applications such antimicrobial, antioxidant, and anticancer activities.

Oil of Oregano benefit
Many studies have been done over the years, but I could only find one involving a human trial. Numerous laboratory and animal studies indicate the health benefit of oregano include immune stimulating effects, blood sugar control properties, antioxidant, anti-fungal, anti-parasite, and anti-bacterial activities. However, since human trials are lacking, the benefit of oregano oil or oregano herb in terms of human disease prevention and treatment. is difficult to say. There are many supplements, herbs or herbal extracts that play a role in immune system support. A few of these include olive leaf extract supplement, colostrum supplement and andrographis.

Q. Is it useful in skin cancer?
   A. I could not find a human study on Medline when I searched for the key words " oregano skin cancer "

Skin care products
Biochim Open. 2017. Anti-inflammatory, tissue remodeling, immunomodulatory, and anticancer activities of oregano (Origanum vulgare) essential oil in a human skin disease model. The use of oregano (Origanum vulgare) essential oil has become popular in skin care products. However, scientific research regarding its effects on human skin cells is scarce. We suggest that oregano oil extract, with carvacrol as the major active component, is a promising candidate for use in skin care products with anti-inflammatory and anticancer properties.

Oil of oregano side effects, danger, is it safe
Q. When I took one dropper full of oil of oregano my tongue became swollen 4 times it's size and I lost my taste buds. I had to go to the ER . I'm on Lidocaine solution to ease the pain My throat is swollen still no taste buds. My tongue 4 times it's original size. I'm hurting . The ER said my mouth and throat burned.
   A. An allergic, hypersensitivity, or irritant reaction can occur if it is not diluted. The side effects subside over a few hours or days depending on the amount used.

Cancer prevention with this plant
Anticancer Drugs. 2015. Carvacrol inhibits proliferation and induces apoptosis in human colon cancer cells. Carvacrol is a major component of oregano and thyme essential oils and shows antitumor properties.

Oregano Plant studies
J Egypt Soc Parasitolology. 2012. The efficacy of Origanum vulgare on Eimeria tenella. Eimeria tenella is one of the most common and pathogenic species of the genus Eimeria in the chicken and is associated with many coccidiosis outbreaks and a high rate of mortality. Experimentally, Origanum vulgare proved to be an anti-Eimeria tenella regimen.

Oregano: properties, composition and biological activity
Arch Latinoam Nutrition. 2004.
The wild oregano spice includes various plant species. The most common are the genus Origanum, native of Europe, and the Lippia, native of Mexico. Among the species of Origanum. their most important components are the limonene, gamma-cariofilene, rho-cymenene, canfor, linalol, alpha-pinene, carvacrol and thymol. In the genus Lippia, the same compounds can be found. The oregano composition depends on the specie, climate, altitude, time of recollection and the stage of growth. Some of the properties of this plant's extracts are being currently studied due to the growing interest for substituting synthetic additives commonly found in foods. Oregano has a good antioxidant capacity and also presents antimicrobial activity against pathogenic microorganisms like Salmonella typhimurium, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, among others. These are all characteristics of interest for the food industry because they may enhance the safety and stability of foods. There are also some reports regarding the antimutagenic and anticarcinogenic effect of oregano; representing an alternative for the potential treatment and/or prevention of certain chronic ailments, like cancer. Oregano oil herb.

Performance of rabbits and oxidative stability of muscle tissues as affected by dietary supplementation with wild oregano essential oil.
Arch Anim Nutr. 2004.
The effect of dietary supplementation with herb oregano essential oil on the performance of rabbits, and the susceptibility of the produced raw and thermally treated muscle tissue to lipid oxidation during refrigerated storage, were investigated. A total of 96 weaned rabbits were separated into four equal groups with three subgroups each. One group was given the basal diet and served as control, two groups were administered diets supplemented with oregano essential oil at levels of 100 and 200 mg/kg diet, whereas the remaining group was given a diet supplemented with alpha-tocopheryl acetate at 200 mg/kg. During the 42-day experimental period, body weight and feed intake were recorded weekly and the feed conversion ratio was calculated. Feeding the experimental diets to rabbits, performance parameters were not affected. Therefore, dietary oregano essential oil exerted no growth-promoting effect on rabbits. With increased supplementation of oregano essential oil, malondialdehyde values decreased in both raw and thermally treated muscles during refrigerated storage. This finding suggests that dietary oregano essential oil exerted a significant antioxidant effect. Dietary supplementation of oregano essential oil at the level of 200 mg/kg was more effective in delaying lipid oxidation compared with the level of 100 mg/kg, but inferior to dietary supplementation of 200 mg alpha-tocopheryl acetate per kg. This study indirectly provides evidence that antioxidant compounds occurring in oregano essential oil were absorbed by the rabbit and increased the antioxidative capacity of tissues.

Anti-hyperglycaemic activity of the aqueous extract of Origanum vulgare growing wild in Tafilalet region.
J Ethnopharmacology 2004.
The effect of an aqueous extract of wild oregano leaves on blood glucose levels was investigated in normal and streptozotocin (STZ) diabetic rats. In normal rats, the blood glucose levels were slightly decreased 6 h after a single oral administration as well as 15 days after once daily repeated oral administration of aqueous wild oregano extract (20 mg/kg). After a single dose or 15 daily doses, oral administration of the wild oregano aqueous extract (20 mg/kg) produced a significant decrease on blood glucose levels in STZ diabetic rats. In STZ rats, the blood glucose levels were normalised from the fourth day after daily repeated oral administration of aqueous wild oregano extract (20 mg/kg). However, this effect was less pronounced 2 weeks after daily repeated oral administration of wild oregano extract. In addition, no changes were observed in basal plasma insulin concentrations after treatment in either normal or STZ diabetic rats indicating that the aqueous Oregano extract acted without changing insulin secretion. We conclude that an aqueous extract of Oregano exhibits an anti-hyperglycaemic activity in STZ rats without affecting basal plasma insulin concentrations.

Immunostimulatory effect of dietary oregano etheric oils on lymphocytes from growth-retarded, low-weight growing-finishing pigs and productivity.
Tijdschr Diergeneeskd. 2004.
The present study was designed to evaluate the possible effect of dietary oregano etheric oils as non-specific immunostimulating agents in growth-retarded, low-weight growing-finishing pigs. Results show dietary oregano improves growth in growth-retarded growing-finishing pigs and has non-specific immunostimulatory effects on porcine immune cells.

Effect of dietary supplementation with oregano essential oil on performance of broilers after experimental infection with Eimeria tenella.
Arch Tierernahr. 2003.
A study was carried out to examine the effect of dietary supplementation of oregano essential oil on performance of broiler chickens experimentally infected with Eimeria tenella at 14 days of age. A total of 120 day-old Cobb-500 chicks separated into 4 equal groups with three replicates each, were used in this study. Two groups, one infected with 5 x 10(4) sporulated oocysts of E. tenella and the other not, were given a basal diet and served as controls. The other two groups also infected with E. tenella were administered diets supplemented with oregano essential oil at a level of 300 mg/kg, or with the anticoccidial lasalocid at 75 mg/kg. Following this infection, survival rate, bloody diarrhoea and oocysts excretion as well as lesion score were determined. Two weeks after the infection with E. tenella supplementation with dietary oregano oil resulted in body weight gains and feed conversion ratios not differing from the non-infected group, but higher than those of the infected control group and lower than those of the lasalocid group. These parameters correspond with the extent of bloody diarrhoea, survival rate, lesion score and oocyst numbers and indicated that oregano essential oil exerted an anticoccidial effect against E. tenella, which was, however, lower than that exhibited by lasalocid.

Antithrombin activity of some constituents from Origanum vulgare - wild oregano plant.
Fitoterapia. 2002.
Aristolochic acid I, aristolochic acid II, and raffinose were isolated from oregano plant. Their inhibition of thrombin and activity against leukemia were evaluated. Aristolochic acid I and II have high inhibition of thrombin activity and were confirmed to possess activity against cancer.

Inhibition of enteric parasites by emulsified oil of oregano in vivo.
Phytother Research. 2000.
Oil of Mediterranean oregano plant was orally administered to 14 adult patients whose stools tested positive for enteric parasites, Blastocystis hominis, Entamoeba hartmanni and Endolimax nana. After 6 weeks of supplementation with 600 mg emulsified oil of oregano daily, there was complete disappearance of Entamoeba hartmanni (four cases), Endolimax nana (one case), and Blastocystis hominis in eight cases. Also, Blastocystis hominis scores declined in three additional cases. Gastrointestinal symptoms improved in seven of the 11 patients who had tested positive for Blastocystis hominis.

Q. What is the safety record of using oil of oregano daily as an immune booster?
   A.  We are not familiar with any long term studies regarding supplement use of oil of oregano. Breaks from use of supplements are often recommended in order to minimize any potential problems that may exist with daily use for prolonged periods. 

Q. Is it okay to use wild oregano oil 6 months of the year during the winter flu season?
   A. I really don't know if oil of oregano use is safe to use for prolonged periods or whether prolonged oregano use leads to side effects. Oregano used reasonably, is probably side effect free, but I prefer taking at least 2 days a week off from an oregano supplement and to avoid continuous use of oregano for more than 2 months at a time.

Q. Can you tell me about oregano and essential oils
   A. I am still learning about essential oils and click the link for more information.

Q. Is Mexican oregano plant different than herbal oregano plant grown other places?
   A. The chemical composition of an herbal plant can be slightly or moderately different depending on which kind of soil it is grown in, the type of fertilizer used, sun exposure, temperature, etc.

Q. I am the administrator of a web site on cystic fibrosis. We have had forums for the past 10 years. I notice the forum members are beginning to use Oil of Oregano with good results. I wonder if you can point me in a direction for a study of oil of oregano and people with cystic fibrosis.
   A. I have not come across any research regarding the use of oil of oregano for cystic fibrosis.

Q. I enjoy your site. Just a comment about the use of oregano in respiratory ailments. I have a decades-long history of severe sinus infections and continued to get these 4 or 5 times a year despite surgery to correct a deviated septum and improve drainage. Needless to say, I was concerned about the continued, repeated use of strong antibiotics to address this issue.  About 18 months ago a friend recommended oil of oregano to me. After trying short-term oregano therapy I am happy to report that I have not needed an antibiotic to cure a sinus infection since discovering this method. I use Oregacyn (softgels and capsules) 4 times day (one capsule, one softgel each time). It consistently wipes out sinus infections within four to five days, and works especially well when combined with a twice-a-day warm saline sinus rinse with a neti pot or other rinsing device. The softgels have the equivalent of about 6 drops of wild oregano oil and I believe this could also be used successfully, though Oregacyn has a few complementary herbs that may provide some additional benefits. Oregacyn is not cheap, but it's been a Godsend after all these years of antibiotic use. I only use it when an infection is present (green gunk), not on a continuous basis. I have no connection with the manufacturer of this Oregacyn product but wanted to post a plug for it because it has really worked wonderfully for me when conventional medicine had little to offer but repeated courses of ceftin, augmentin, biaxin ad infinitum.
     A. Thank you for sending your anecdote.

Q. Dear Dr. I've read all you write on the Oil of Oregano and the daily dosage, but how long do we take it for. 10 days, 2 wks, 3 wks. etc. Thank YOU for all you do.
   A. There is no right or wrong answer on how to take oil of oregano. Each person is unique in their requirement depending on what they treating or preventing or what other supplements they are taking, or what kind of diet they have. For general immune health maintenance, using oil of oregano 2 or 3 times a week seems safe.

I will be interested to know if my husband who was just diagnosed with gleason 6 on one lobe and gleason 7 on other lobe (3+3), (3+4), could safely use oil of oregano. How many times a week?
    I can't give specific advice, but, as a general rule, oil of oregano is a safe supplement when diluted appropriately according to the instructions on the bottle, but his doctor would have to approve.

I stumbled upon your website while doing some research on elderberry supplements after it was recommended by Dr. Oz on tv. I was worried about bacterial infection which I might have picked up from washing a sick dog in July 2009. The dog died. I have had numerous blood tests since then and all come back normal / negative but have had some symptoms (headaches, itchy acne-like skin bumps on the neck, lactose intolerance, etc). Consequently, the doctors I have seen are unconcerned and think I am imagining an illness. I think symptoms usually indicate risk and an ounce of prevention is worth a pound of cure. I don't blood bacteria to eat my brain like it did the dog. So I tried the elderberry product Sambucol to boost immunity (as well as eating lots of garlic, cranberry juice, etc) and have also purchased Oil of Oregano which is supposed to be (according to my internet research) a herbal antibiotic as effective as the strongest prescription antibiotics. Just curious if you have any advice about taking the oil of oregano and elderberry - ie. how long should it be taken, how should the oil be taken - topical or mixed in food, should acidophilus be taken with it to keep up the "good bacteria", what is "good bacteria", etc.
    These are all good questions and there are no easy answers since each person may respond differently depending on their age, diet, other supplements used, other medications taken, etc. Oil of oregano is a good product for the immune system but it is not as effective as the strongest prescription antibiotic.

buy Oil of Oregano Supplement
Source Naturals
Oregano Supplement Facts:
Serving Size 4 Drops
Servings Per Container 275
Amount Per Serving:                                                   
Wild Oregano Oil 37.6 mg
    (Origanum vulgare herb) Yielding approximately 22.6 mg of carvacrol
Extra Virgin Olive Oil - 70 mg

Purchase Oregano Oil supplement

Suggested Use or dosage : 1 to 4 oil of oregano drops in water, juice or milk once or twice daily.  Oregano oil may also be used topically. Do not use this product undiluted.