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Oregano: benefits, dosage, side effects

23 Nov 2022 • 1 min read

Find out all about oregano, including what it does, the benefits to taking it and how much you might need

Written by Jack Feeney on January 7, 2019 Reviewed by Gabriella Clarke on January 24, 2019


What is oregano and what does it do?

Oregano is a fragrant herb growing in mountainous Mediterranean regions. It’s well-known for its use in Italian, Greek and Spanish cooking, but it doesn’t just taste good. Historically, oregano has been used as a herbal medicine for indigestion and as an antiseptic. Nowadays, it’s used as a natural antibiotic and an antifungal.1 It’s also a good source of vitamin K – needed for blood-clotting and strong bones. A teaspoon of oregano contains 8% of your recommended daily amount of vitamin K. Oregano is available as a fresh or dried herb, or in capsules. It can also be used as a highly concentrated essential oil, so remember to dilute it first.

Benefits of oregano

What does oregano do in the body?

The main active ingredients in oregano are two powerful antioxidants:3
  • carvacrol
  • thymol
Antioxidants help prevent free radicals from causing oxidative damage to our cells, which is linked to conditions such as heart disease and dementia. Oregano may also be an effective:
  • antifungal – in 2007, Japanese researchers tested the effectiveness of 11 different essential oils against the fungi that cause athlete’s foot, and oregano was found to be the most successful,4 while a 2001 study by the Georgetown University Medical Center, Washington, reported that oregano oil inhibited the growth of C. albicans – the fungal yeast that can trigger thrush – by up to 75%5
  • antibacterial – a 2009 study by the University of Karachi in Pakistan pitted oregano oil against 23 different types of bacteria, including staphylococcus saprophyticus, and oregano ‘won’6
  • antiviral – according to a laboratory study in the Journal of Applied Microbiology in 2014, carvacrol inactivated the norovirus – the winter vomiting bug within an hour,7 while a Taiwanese study in Planta Medica in 2012 found that a combination of thymol and carvacrol could disable the herpes simplex type 1 virus that causes cold sores by 90% in the same time8
  • antiseptic – in 2011, Israeli researchers discovered that a spray containing oregano oil significantly improved the symptoms of upper respiratory tract infections, such as sore throat, hoarseness and coughing, in 60 patients within 20 minutes9
Scientists believe that oregano has these properties because both carvacrol and thymol can attack the membrane of a bacteria cell, leading to its destruction.10


How much oregano is safe to take?

No safe upper limit has been established for oregano, so make sure you stick to any guidelines on packaging, leaflets or bottles of oregano essential oil. However, it is not safe for women who are pregnant or breast-feeding. Children over 12 can take it, but seek advice from a qualified medical herbalist for younger children. If you are allergic to plants in the Lamiaceae family, like lavender, mint, sage and basil, avoid taking or using oregano.11


What are the side-effects of taking oregano?

The normal amount of fresh or dried oregano you use in food is unlikely to cause any side-effects. But you need to be more cautious when using oregano oil – its high concentration means a larger amount of active ingredients, in particular thymol, which can cause irritation at high doses.12 Side-effects of taking or using oregano can include:13
  • feeling sick
  • vomiting
  • gastric problems
When applied topically, diluted oregano oil may cause a skin rash. Stop using if this happens and ask your GP or medical herbalist for advice. Shop Supplements Advice is for information only and should not replace medical care. Please check with your GP before trying any remedies. Sources 1. Alexandra Rowles. Healthline 2. Nutrition Data. Spices, oregano, dried Nutrition Facts and Calories 3. Terenina MB, et al. Oregano essential oil as an inhibitor of higher fatty acid oxidation 4. Inouye S, et al. Combined effect of heat, essential oils and salt on fungicidal activity against Trichophyton mentagrophytes in a foot bath 5. Manohar V, et al. Antifungal activities of origanum oil against Candida albicans 6. Saeed S, Tariq P. Antibacterial activity of oregano (Origanum vulgare Linn.) against gram positive bacteria 7. Gilling GH, et al. Antiviral efficacy and mechanisms of action of oregano essential oil and its primary component carvacrol against murine norovirus 8. Lai WL, et al. Inhibition of herpes simplex virus type 1 by thymol-related monoterpenoids 9. Ben-Arye E, et al. Treatment of upper respiratory tract infections in primary care: a randomized study using aromatic herbs 10. Levya-Lopez N, et al. Essential Oils of Oregano: Biological Activity beyond their Antimicrobial Properties 11. Corey Whelan. Healthline. Oregano Oil Side Effects 12. As above 13. As Source 11
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