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Pennyroyal (Mentha pulegium)
A mint-family herb used historically as an abortifacient, and a documented cause of fatal liver failure. This entry exists so that pennyroyal can be SCREENED — it is never recommended, and the oil in particular has no safe dose.
Research compound — not a dietary supplement
Pennyroyal is a research compound, not a regulated dietary supplement. It is sold for research or off-label use. The evidence below is largely preclinical (animal and in-vitro) or early-stage, so no evidence score is assigned. This page is provided for transparency and education — it is not a recommendation to use. Consult a qualified healthcare provider, and be aware that purity, dosing, and legal status vary by jurisdiction.
What the evidence says
Pennyroyal doesn't have enough studies with structured effect-size data yet to pool a verdict. Browse the studies below for individual findings.
Most evidence is from high-quality studies published 1996–2015.
Based on 2 studies
Confidence
Very low confidenceBy outcome
Scores at the floor because no controlled human evidence supports any use. The literature is toxicological: measured metabolite levels in human poisoning, and three decades of mechanistic work on how pulegone injures the liver.
Pennyroyal (Mentha pulegium) looks and smells like an ordinary mint and is not one in the ways that matter.
Its principal constituent, pulegone, is converted by CYP450 enzymes to menthofuran and other reactive metabolites that deplete hepatic glutathione and bind covalently to liver protein — the same acute metabolism-based mechanism that makes paracetamol overdose dangerous.
Ingestion of the concentrated oil has caused fulminant hepatic failure and death, and the herb's historical use as an abortifacient means the exposures reported are often deliberate and large.
It is carried here as a screenable entry rather than as an option: flagged `researchCompound`, no goal mappings, excluded from every recommendation flow. A reader who scans or types the name is told what it is, instead of being told it could not be identified.
CYP450 enzymes convert pulegone to menthofuran and further reactive metabolites, which deplete glutathione and bind covalently to liver protein.
The historical abortifacient use, which is why reported exposures tend to be deliberate and large.
Avoid — abortifacient, and hepatotoxic to the mother. There is no amount of the oil that is safe.
Avoid — pulegone and its reactive metabolites are pharmacologically active and there is no safety data for the nursing infant.
Avoid — the injury mechanism is hepatic and a damaged liver has less reserve.
Avoid — never give this herb to a child.
Both deplete hepatic glutathione through reactive metabolites; the liver injury is additive.
Induction increases conversion of pulegone to its toxic metabolites.
Tip: Do not take this herb; seek medical care after any ingestion of the oil
Tip: Emergency medical care — this has been fatal
The current evidence for Pennyroyal is insufficient to assign an evidence score, based on 2 indexed studies. A mint-family herb used historically as an abortifacient, and a documented cause of fatal liver failure. This entry exists so that pennyroyal can be SCREENED — it is never recommended, and the oil in particular has no safe dose. Representative study: PMID 8633832.
The commonly studied dose of Pennyroyal is No appropriate dose. This entry exists so the herb can be screened, not taken.. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
Timing is flexible for Pennyroyal — consistent daily use matters more than the time of day. No dose is appropriate; no timing guidance is given.
Pennyroyal should be used with caution — talk to a healthcare provider before taking it. The most commonly reported side effects are nausea, vomiting, abdominal pain, acute liver failure. Use caution if any of these apply to you: Pregnancy — do not take; abortifacient and hepatotoxic; Breastfeeding — do not take; Any liver disease.
Blue Cohosh
Too few graded studiesA herb traditionally used to induce labour, and a serious teratogen. This entry exists so that blue cohosh can be SCREENED — it is never recommended, and there is no dose at which it is appropriate in pregnancy or breastfeeding.
Comfrey
Too few graded studiesA traditional poultice herb containing unsaturated pyrrolizidine alkaloids, which are hepatotoxic and carcinogenic. This entry exists so that comfrey can be SCREENED — it is never recommended, and internal use has caused fatal hepatic veno-occlusive disease.
Psyllium Husk
Likely helpsGel-forming soluble fiber that lowers LDL cholesterol, regulates blood sugar, and promotes digestive regularity.
St. John's Wort
Mixed evidenceModulates serotonin, dopamine, and norepinephrine; studied for mood, with trials in mild-to-moderate depression comparing it to SSRIs — requires drug-interaction caution.
Reviewed by Dr. Baher Al Hakim · Last reviewed August 2026 · evidence from 2 studies · how we score · editorial policy
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.