Supplement analysis backed by scientific evidence · PT

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Limited evidenceGut health

Oregano Oil

Oregano oil is a genuinely potent antimicrobial in a petri dish and almost untested in humans — one 14-person open-label parasite study is the most-cited clinical evidence there is. Treat the SIBO, candida and "natural antibiotic" claims as unproven.

What the science says

  • Intestinal parasites and gut microbes Limited evidence

    The single most-cited human study gave 600 mg/day of emulsified oregano oil for 6 weeks to 14 adults with enteric parasites; Blastocystis hominis cleared in 8 of 11 cases and GI symptoms improved in 7 of 11. It was uncontrolled, unblinded and tiny — hypothesis-generating at best, and it has never been replicated in a randomized trial.

  • Antibacterial and antifungal activity Limited evidence

    Carvacrol and thymol disrupt bacterial membranes and inhibit Staphylococcus aureus, E. coli, Candida albicans and many others at low concentrations in vitro, which is why oregano oil dominates laboratory antimicrobial screens. Reaching those concentrations in the human gut or bloodstream after oral dosing has not been demonstrated, and no clinical trial shows it treats an infection.

  • SIBO and candida protocols Limited evidence

    Oregano oil is a staple of herbal SIBO protocols, but the trial usually cited for these regimens tested multi-herb combinations, not oregano oil alone, so no effect can be attributed to it. There is no controlled evidence at all for oral oregano oil in candida overgrowth.

Dosage & safety

Studied doseThe parasite study used 600 mg/day of emulsified oregano oil for 6 weeks. Commercial capsules typically supply 100-600 mg/day of oil standardized to 50-85% carvacrol, or a few drops of diluted oil, usually for 2-4 weeks. No dose has been validated in a randomized trial, and undiluted essential oil should never be swallowed.
SafetyUndiluted oregano essential oil is caustic and can burn the mouth, oesophagus and skin — always dilute or use enteric capsules. Common effects are heartburn, nausea and burping. It may lower blood glucose and has antiplatelet activity in vitro, so use caution with antidiabetic drugs, anticoagulants and before surgery. It can reduce iron absorption when taken with meals. People allergic to Lamiaceae plants (mint, basil, sage, lavender) may react. Avoid in pregnancy — traditional use as an emmenagogue and animal data raise concern — and do not give to infants or young children. It is antibacterial without selectivity, so prolonged use as a routine "gut cleanse" is not benign.

Scientific references

Where to buy

NOW Foods, Oregano Oil, 90 Softgels

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