Essential Oils, the Liver and Kidneys and Medicine Cautions
Which liver and medicine concerns with essential oils are documented in case reports, which are only laboratory findings, and where the sources we read say nothing.
Content last updated . This page has not been medically reviewed.
Safety first. Supplements can cause side effects and interact with medicines. Read mushroom safety and interactions before you use any mushroom product.
Urgent first
If an essential oil has been swallowed, call Poison Help at 1-800-222-1222. Poison Control says swallowed pennyroyal oil is highly poisonous to the liver. [1] Call 911 for collapse, seizure or trouble breathing. A person taking warfarin or another blood thinner who notices unusual bleeding or bruising after using a rub should contact the prescriber, pharmacist or emergency services.The short answer
Few essential-oil liver or medicine problems are documented in the sources we could read, and the best-documented ones involve swallowing (pennyroyal) or a methyl salicylate product used with warfarin. Much else is theoretical or comes from laboratory work. Poison Control states in general terms that essential oils may interact with medications. [1] For how interactions are graded, see how interactions work.Documented, reported and theoretical
| Concern | What the source found | Strength of evidence |
|---|---|---|
| Pennyroyal oil and the liver | Pennyroyal has long been used as an abortifacient despite potentially lethal liver toxicity. [2] A review of 18 earlier case reports documented moderate to severe toxicity in patients exposed to at least 10 mL of pennyroyal oil. [2] | Evidence of harm (case reports and a case series of swallowing). See pennyroyal oil. |
| Wintergreen oil (methyl salicylate) swallowed | Poison Control says wintergreen oil is very dangerous if more than a tiny amount is swallowed. [1] A review says ingestion poses a threat of severe, rapid-onset salicylate poisoning. [3] | Evidence of harm (reports). See wintergreen oil. |
| Methyl salicylate rubs and warfarin | A review says excessive use of such preparations in people taking warfarin may result in adverse interactions and bleeding. [3] A case report describes an INR of 12.2 after a woman used a topical pain-relieving gel on her knees daily for eight days. [4] Methyl salicylate is absorbed through the skin in measurable amounts. [4] | Documented in case reports. One case is not a rate. The product was a gel containing methyl salicylate, not a pure essential oil. |
| Lavender oil and medicine-processing enzymes | In human liver preparations in a laboratory, lavender oil weakly inhibited the enzymes CYP3A4 and CYP1A2. [5] The authors concluded this suggests little potential to change how conventional medicines work if used together. [5] | Preclinical (cells or lab preparations). Not a human trial. |
| Children's livers | Poison Control says children have thin skin and immature livers, which might make them more susceptible to toxic effects. [1] | Expert statement (general), not specific to one oil. |
| Other ingredients | Poison Control says toxicity could come from other ingredients, such as other oils or alcohol, depending on how a product is made. [1] | Expert statement |
Where we found nothing
- Clove oil and the liver: Proper evidence not found. We searched PubMed for clove oil, eugenol, liver injury and child ingestion and found no usable report. The NIH LiverTox database, which would be a main source, would not load for us (it showed a browser check), so we make no claim from it.
- Kidneys: Proper evidence not found. We searched PubMed for essential oils and kidney injury and found only a 1998 letter with no abstract available, so we say nothing about it.
- Tea tree, eucalyptus, peppermint and medicines: the sources we read for this page do not describe documented interactions. That is not proof of safety.
- Which medicine groups are affected: the only medicine named in the sources we read is warfarin. For the full picture see interactions by drug class and essential oils and medicines.
Why contents matter
Each oil has a unique chemical composition, and that affects its smell, absorption and effects on the body. [6] Poison Control adds that it can be hard to know exactly what species, concentration or contaminants are in an essential oil bottle. [1] See product quality.Frequently asked questions
Can essential oils damage the liver?
Swallowed pennyroyal oil is documented to be highly poisonous to the liver. [1] We did not find usable reports for most other oils.
Is it safe to use a wintergreen rub with warfarin?
Case reports describe raised INR with methyl salicylate products in people taking warfarin. [4] Ask a pharmacist.
Do essential oils interact with medicines?
Poison Control says they may. [1] Few specific interactions are documented in the sources we read.
Do lab findings about enzymes matter?
They are a reason to ask, not proof of a problem. In one lab study, lavender oil had weak effects on two enzymes. [5]
Do I need to tell my surgeon?
Yes, mention any oils or rubs you use regularly.
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety and who should ask a clinician
- Liver or kidney disease, or taking regular medicines: ask a pharmacist or the prescriber before using oil-containing rubs or products, and say which product and which botanical name.
- Warfarin and other blood thinners: methyl salicylate products need a pharmacist's advice.
- Before surgery: tell the surgical team about any oils or rubs. See supplements before surgery.
- Pregnancy and children: see pregnancy and breastfeeding and babies and children.
- Never stop or change a prescribed medicine because of an oil. Ask the prescriber or pharmacist. This page gives no amounts.
References
- Essential oils: Poisonous when misused, Poison Control (US). Read 2026-10-23.
- Pennyroyal toxicity: measurement of toxic metabolite levels in two cases and review of the literature, Anderson IB et al., Ann Intern Med 1996, PMID 8633832. Read 2026-10-23.
- Potential dangers from topical preparations containing methyl salicylate, Chan TY, Hum Exp Toxicol 1996, PMID 8880210. Read 2026-10-23.
- Potentiation of warfarin anticoagulation associated with topical methyl salicylate, Joss JD and LeBlond RF, Ann Pharmacother 2000, PMID 10860133. Read 2026-10-23.
- In Vitro Metabolism and CYP-Modulating Activity of Lavender Oil and Its Major Constituents, Mondal G et al., Molecules 2023, PMID 36677813. Read 2026-10-23.
- Essential Oils, National Institute of Environmental Health Sciences (NIH), last reviewed March 19, 2026. Read 2026-10-23.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.