Clove Oil: Side Effects and Cytotoxicity Explained
Among the most powerful essential oils in aromatherapy, clove oil comes with well-documented effects, from simple irritation to a serious accidental ingestion.
Our article clove oil: dangers, dilution and precautions already set the general framework of caution for this essential oil. This companion piece details the documented side effects, from the most common (local irritation) to the most serious (ingestion), for clove oil.
What the laboratory cytotoxicity study shows
A study by Prashar, Locke and Evans, published in 2006 in Cell Proliferation, measured the effect of clove essential oil and its main component, eugenol, on human skin-cell cultures (see the study on Google Scholar). The result: marked cell toxicity at concentrations close to those found in undiluted use, which led the authors to recommend strict dilution before any contact with skin or mucous membranes. This laboratory finding explains the burning sensation reported by many users when the oil is applied neat, especially on the gum.
A documented case of liver failure after ingestion
A serious poisoning was documented by Janes and colleagues in 2005: a child who ingested clove essential oil developed acute liver failure, treated as an emergency with N-acetylcysteine, the antidote usually used for paracetamol poisoning (see the case on Google Scholar). This case is a reminder that eugenol, even at a modest ingested dose in a child, can carry serious liver toxicity — a radical difference from diluted skin use, where the absorbed quantity is nowhere near comparable.
Catalogue of possible side effects
| Effect | Context | Severity |
|---|---|---|
| Burning or tingling sensation | Undiluted application, especially on the gum | Common if undiluted, reversible |
| Skin irritation | Insufficient dilution on sensitive skin | Occasional |
| Localized tissue damage | Repeated undiluted application on a mucous membrane | Rare but documented |
| Liver failure | Ingestion, especially in a child | Rare but serious, documented case |
Reducing the risk in practice
- Never apply undiluted on the gum or skin, including for occasional dental use;
- Dilute heavily (1% maximum) before any skin or dental use;
- Keep out of children's reach: a bottle of essential oil poses a risk of severe accidental ingestion;
- Seek emergency care in case of ingestion, even a small amount, without waiting for symptoms to appear.
These pointers complement our article clove oil: dangers, dilution and precautions. General precautions are gathered in our safety and precautions guide.
Your questions about clove oil
Why does clove oil burn on the gum?
A 2006 laboratory study showed marked cell toxicity of eugenol, the oil’s main component, on human skin-cell cultures at concentrations close to undiluted use — hence the burning sensation with neat application.
Is ingesting clove oil dangerous?
Yes, a documented 2005 case describes acute liver failure in a child after ingestion, treated as an emergency. The bottle must stay out of children’s reach and the oil should never be swallowed.
Can I use undiluted clove oil on an aching tooth?
No, not even for occasional use. Strict dilution (1% maximum) is recommended before any contact with the gum, to avoid irritation or localized tissue damage from repeated use.
What should I do if clove oil is accidentally ingested?
Seek emergency care, even for a small amount and even without immediate symptoms, given the documented liver risk in children.
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