Eugenol

Other Names

1,3,4-Eugenol1-Allyl-3-methoxy-4-hydroxybenzene1-Allyl-4-hydroxy-3-methoxybenzene1-Hydroxy-2-methoxy-4-allylbenzene1-Hydroxy-2-methoxy-4-prop-2-enylbenzene1-Hydroxy-2-methoxy-4-propenylbenzene2-Hydroxy-5-allylanisole2-Methoxy-1-hydroxy-4-allylbenzene2-Methoxy-4-(2-propen-1-yl)phenol2-Methoxy-4-(2-propenyl)phenol2-Methoxy-4-(3-propenyl)phenol2-Methoxy-4-(prop-2-en-1-yl)phenol2-Methoxy-4-allylphenol2-Methoxy-4-prop-2-enylphenol3-(3-Methoxy-4-hydroxyphenyl)propene4-(2-Propenyl)-2-methoxyphenol4-Allyl-1-hydroxy-2-methoxybenzene4-Allyl-2-methoxyphenol4-Allylcatechol 2-methyl ether4-Allylguaiacol4-Hydroxy-3-methoxy-1-allylbenzene4-Hydroxy-3-methoxyallylbenzene5-AllylguaiacolAllylguaiacolCaryophillic acidCaryophyllic acidEngenolEugenic acidEugenoloEugenolump-Allylguaiacolp-EugenolPhenol, 2-methoxy-4-(2-propen-1-yl)-Phenol, 2-methoxy-4-(2-propenyl)-Phenol, 4-allyl-2-methoxy-

Synopsis

Eugenol: A Comprehensive Reference Article

1. Identity and Chemical Profile

Chemical Names and Classification

Eugenol (C₁₀H₁₂O₂; phenylpropanoid) is an aromatic compound belonging to the group of phenols. More specifically, eugenol is an allyl chain-substituted guaiacol, a member of the allylbenzene class of chemical compounds. Its systematic IUPAC name is 4-allyl-2-methoxyphenol; it is also formally designated 2-methoxy-4-(2-propenyl)phenol. Synonyms include 4-allyl-2-methoxyphenol, p-allylguaiacol, p-eugenol, caryophyllic acid, engenol, eugenic acid, and 2-methoxy-1-hydroxy-4-allylbenzene. The CAS registry number is 97-53-0. The name "eugenol" is derived from Eugenia caryophyllata, the former Linnean nomenclature for cloves; the currently accepted name for the clove tree is Syzygium aromaticum.

Eugenol is a phenylpropene — specifically, an allyl chain-substituted guaiacol — and a member of the phenylpropanoids class of chemical compounds. It is a colorless to pale yellow, aromatic oily liquid extracted from certain essential oils, especially from clove, nutmeg, cinnamon, basil, and bay leaf. Eugenol is generally well soluble in organic solvents and sparingly soluble in water.

The biosynthesis of eugenol in plants begins with the amino acid tyrosine. Phenylpropenes such as eugenol are produced by plants as defense compounds against animals and microorganisms and as floral attractants of pollinators. At the enzymatic level, glandular trichomes of sweet basil (Ocimum basilicum), which synthesize and accumulate phenylpropenes, possess an enzyme that can use coniferyl acetate and NADPH to form eugenol.

Natural Sources and Concentrations

Eugenol is commonly obtained from the natural essential oils of plants from the Lamiaceae, Lauraceae, Myrtaceae, and Myristicaceae families, and is the most important component of clove oil (Syzygium aromaticum), where it constitutes between 9,381.7 mg and 14,650 mg per 100 g of fresh plant material and is primarily responsible for its characteristic aroma. It is present in concentrations of 80–90% in clove bud oil and 82–88% in clove leaf oil.

Beyond clove, eugenol occurs in a wide range of other species. Eugenol also occurs in allspice (Pimenta dioica), nutmeg (Myristica spp.), cinnamon (Cinnamomum spp.), and basil (Ocimum basilicum). Further aromatic plants containing eugenol include Cinnamomum tamala, Myristica fragrans, Melissa officinalis, Ocimum basilicum, Ocimum tenuiflorum, Illicium anisatum, and Cinnamomum verum. Eugenol is also found in cinnamon bark and leaves, Tulsi leaves, turmeric, pepper, ginger, oregano, and thyme, among various other herbs.

Commercial Production and Isolation

Eugenol was first isolated from clove oil in 1929, and the extraction method was employed for commercial production in the 1940s in the United States. Commercial eugenol is preferentially isolated from clove leaf oil and cinnamon leaf oil through extraction with sodium hydroxide solution, followed by removal of nonphenolic materials via steam distillation. Eugenol is extracted from essential oils by the steam distillation process and then concentrated to yield pure eugenol (>95%); the technical product contains 95–100% eugenol. Eugenol can also be synthesized chemically by allowing allyl chloride to react with guaiacol; however, enough quantity of eugenol is extracted from essential oils, which is cheaper than industrial synthesis.

Common Forms and Preparations

Eugenol is encountered in several forms depending on its application:

Crude clove essential oil: The essential oil is extracted through steam distillation of clove buds, leaves, and stems.
Isolated pure eugenol: Extracted from essential oils by steam distillation and concentrated to yield pure eugenol (>95%).
Zinc oxide–eugenol (ZOE) dental materials: Clinically approved formulations of eugenol, such as products of zinc oxide-eugenol, are available on the market and used in dentistry as an endodontic sealer for non-surgical root canal treatment.
Food additive / flavoring: Eugenol is an active ingredient in clove essential oil and is a generally recognized as safe (GRAS)-certified food ingredient.
Topical and cosmetic preparations: Eugenol appears in a wide range of consumer products including food and beverages, cosmetics and skincare, household products, and dental products such as toothache gels, mouthwashes, and temporary filling materials.

2. Traditional and Historical Use

Asia: China and Ayurveda

Since ancient times, clove has been used as a spice and fragrance in Asian countries. Humans have used phenylpropenes since antiquity for food preservation and flavoring and as medicinal agents. Ancient Chinese texts reference "Ji She Xiang," highlighting clove's esteemed status; during the Han Dynasty, courtiers were required to chew cloves before approaching the emperor to ensure fresh breath — a testament to cloves' antibacterial qualities.

In Ayurvedic medicine, clove is known as Lavanga and has been employed across multiple therapeutic areas. Cloves contain eugenol, a compound widely used as an analgesic and local anesthetic, particularly in dentistry. Clove oil provides significant benefit for toothaches and has natural analgesic, antiseptic, and antibacterial properties; it is used in the preparation of some toothpastes and Clovacaine solution, a local anesthetic used in oral ulceration and inflammation. Conventionally, eugenol has been endorsed in traditional systems to address diarrhea, bronchitis, hyperlipidemia, hyperglycemia, arthritis, inflammation, liver ailments, cancer, cardiovascular conditions, and skin diseases.

Indonesia and Southeast Asia

By the 14th century, the Serat Centhini (a vast Javanese encyclopedia of local culture, medicine, and mysticism) mentions a warming oil called "tel lawang" used by royal healers, who believed the strong potency of clove warmed the chest, relieved toothache, and boosted mental clarity. During the Dutch colonial period in the 17th–19th centuries, physicians in Batavia (present-day Jakarta) combined local methods with European distillation techniques; these hybrid preparations were sometimes standardized in early pharmacopoeias describing 1 part clove buds to 4 parts sesame or coconut oil, heated gently to release eugenol.

Dental Applications Across Traditions

Cloves are used in traditional medicine as an essential oil intended to be an anodyne (analgesic) mainly for dental emergencies; there is evidence that clove oil containing eugenol is effective for toothache pain and other types of pain. The use of eugenol in dentistry as a formalized material has deep historical roots: zinc oxide eugenol (ZOE) was discovered by Bonastre in 1837, subsequently used in dentistry by Chisolm in 1876, and until 2008 the American Academy of Pediatric Dentistry (AAPD) explicitly recommended ZOE as the only primary root canal filling material.

3. Key Constituents, Chemistry, and Mechanisms of Action

Chemical Structure and Related Compounds

Eugenol (C₁₀H₁₂O₂) is a phenylpropanoid, an aromatic compound belonging to the phenol group. The molecule consists of a guaiacol (methoxyphenol) ring with an allyl side chain at the para position. This hydroxyl group and allyl chain are the structural elements principally responsible for both its biological activity and its capacity for oxidative transformation. Within the clove essential oil, eugenol is accompanied by minor constituents including eugenyl acetate and β-caryophyllene; roughly 89% of the clove essential oil is eugenol, and 5–15% is eugenyl acetate and β-caryophyllene.

Analgesic and Local Anesthetic Mechanisms

Eugenol's analgesic effects are mediated by at least two distinct ion-channel mechanisms. Eugenol is useful as a local anesthetic in dentistry because of its ability to allay tooth pain through inhibition of the voltage-gated sodium channel (VGSC) and activation of the transient receptor potential vanilloid subtype 1 (TRPV1).

Regarding VGSC inhibition, a published electrophysiological study demonstrated that using a whole-cell patch-clamp technique investigating the effect of eugenol on voltage-gated sodium channel currents in rat dental primary afferent neurons, eugenol inhibited action potentials and sodium currents in both capsaicin-sensitive and capsaicin-insensitive neurons. These results demonstrated that eugenol inhibits sodium currents in a TRPV1-independent manner, and this inhibition contributes to its analgesic effect.

Regarding TRPV1 modulation, a network pharmacology and molecular docking study found that eugenol could spontaneously bind to the TRPV1 receptor with high binding affinity, increasing the expression of TRPV1 in cells and activating TRPV1; upon continued exposure, eugenol acts as a TRPV1 agonist, increasing intracellular Ca²⁺ levels, which is associated with desensitization of pain sensations.

Anti-inflammatory Mechanisms

The mechanisms associated with the anti-inflammatory and antioxidant effects of eugenol converge on the regulation of transcription factors and pro-inflammatory cytokines, as well as endogenous molecules that constitute the antioxidant defense system.

A key pathway is NF-κB inhibition. Eugenol is capable of acting on the inhibition of adapter proteins such as myeloid differentiation factor 88 (MyD88), suppression of the activation of the IKK complex, and inhibition of the phosphorylation of p65 and IκB, preventing the NF-κB heterodimer from being translocated to the nucleus to induce gene expression.

Cyclooxygenase and lipoxygenase inhibition have also been proposed. In silico bioinformatics studies found that eugenol may inhibit both COX-2 and 5-LOX. It is therefore possible that eugenol may act as an anti-inflammatory agent analogous to some NSAIDs in various diseases, and could also be used in the synthesis of new selective drugs to fight diseases associated with inflammatory processes, such as osteoarthritis or cancer.

Antioxidant Mechanisms

Eugenol can activate antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) under conditions of oxidative stress. It also acts by inhibiting the ubiquitination and degradation of the Keap1-Cul3-Nrf2 complex; eugenol stimulates Nrf2 activation so that Nrf2 is released from the Keap1-Cul3 complex and translocated to the nucleus, where it binds to antioxidant response elements (ARE) leading to the transcription of antioxidant genes.

This Nrf2 pathway activation is supported at the molecular level: among natural compounds tested, eugenol was found to increase the transcriptional activity and expression level of Nrf2, a central regulator of cellular responses to oxidative stress, in a dose-dependent manner; the mRNA levels of Nrf2 target genes were also found to be upregulated following eugenol treatment.

Antimicrobial Mechanisms

Both clove oil and eugenol express significantly inhibitory effects on numerous kinds of food-source microorganisms, and the mechanisms are associated with reducing migratory and adhesion capacity and inhibiting the synthesis of biofilm and various virulence factors of these microorganisms.

Against fungi, the primary mechanism involves membrane disruption. Eugenol acts on the cell membrane by a mechanism that seems to involve the inhibition of ergosterol biosynthesis; the lower ergosterol content interferes with the integrity and functionality of the cell membrane.

4. Scientific Evidence by Area of Use

4.1 Dental Analgesia and Endodontics

Eugenol's application in dentistry has the deepest body of clinical evidence of any of its uses. One review reported the efficacy of eugenol combined with zinc oxide as an analgesic for alveolar osteitis (dry socket). A 2025 systematic review on phytotherapeutic agents in dental pain management found that eugenol demonstrated efficacy in preventing alveolar osteitis, and for endodontic applications, four studies focused on postprocedural endodontic pain found eugenol and propolis showing significant benefits.

The zinc oxide–eugenol (ZOE) formulation has been evaluated in multiple clinical trials as a root canal filling material in primary (deciduous) teeth. A randomized clinical trial involving 120 primary second molars treated by electrosurgical pulpotomy randomly assigned to ZOE or zinc polycarboxylate (ZPC) cement and evaluated clinically and radiographically at 3, 6, and 12 months found that at 12 months the clinical and radiographic success rates in the ZOE group were 98.2% and 84.2%, respectively, with no statistically significant difference between groups (P > 0.05).

Another controlled study evaluating ZOE and Metapex as root canal filling materials in 42 necrotic primary teeth in children aged 4–7 years, followed for 6 months, found overall success rates of 85.71% for ZOE and 90.48% for Metapex, with both materials producing encouraging results.

A systematic review and meta-analysis examining calcium hydroxide/iodoform paste versus ZOE as filling materials, which identified 15 articles meeting all inclusion criteria from 5,000 articles, concluded that more high-quality randomized controlled clinical trials with long-term follow-up are needed before a reliable conclusion can be drawn as to the best pulpectomy material in primary teeth. The authors noted that zinc oxide eugenol or zinc oxide eugenol/iodoform combined with calcium hydroxide appears to be the material of choice if primary teeth are not nearing exfoliation.

Evidence strength (dental): Moderate-to-strong for the ZOE dental formulations; multiple randomized clinical trials and systematic reviews exist. Evidence for pure topical eugenol or clove oil in acute toothache is supported by mechanistic studies and limited clinical comparisons but lacks large-scale, placebo-controlled trial data for non-formulated preparations.

4.2 Anti-inflammatory and Antioxidant Activity

Studies have demonstrated that eugenol has anti-inflammatory, analgesic, and antioxidant properties, with potential use in the treatment of cancer, inflammatory bowel diseases, kidney and lung injuries, and osteoarthritis. However, the preponderance of this evidence comes from animal and cell-culture models. A 2018 PubMed-based review covering publications from January 2008 to January 2018 discussed eugenol's role in the inflammatory response in experimental models, including animals and cell culture tests, demonstrating its antioxidant profile and potential therapeutical application against inflammatory diseases.

In arthritis models, a study by Adefegha et al. (2018) revealed that eugenol was able to restore the activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione S-transferase (GST) in the liver of rats with arthritis; these enzymes are endogenous antioxidant factors considered the first line of defense against the formation of free radicals.

Evidence strength (anti-inflammatory/antioxidant): Predominantly preclinical (animal and in vitro). No large-scale human randomized controlled trials for systemic anti-inflammatory applications had been completed as of the most recent reviews. The mechanistic basis is well-characterized at the molecular level, but translation to human clinical benefit for chronic inflammatory conditions remains to be established.

4.3 Antimicrobial Activity

Several pharmacological activities have been reported to eugenol, including antibacterial, antifungal, antipyretic, anesthetic, and analgesic activities.

Antibacterial: A published MIC study reported that the minimum inhibitory concentration (MIC) against bacteria was found to be 1000 µg/mL for eugenol in broth dilution assays. Against specific food pathogens, both clove oil and eugenol express significantly inhibitory effects on numerous kinds of food-source microorganisms, with mechanisms associated with reducing migratory and adhesion capacity and inhibiting the synthesis of biofilm and various virulence factors.

Antiviral: Eugenol has demonstrated antiviral activity; it acts synergistically with acyclovir in inhibiting the herpes virus in vitro and against HSV-1 and HSV-2 by preventing viral replication and limiting viral infection. This evidence is in vitro only.

Antifungal: A study investigating eugenol against 14 strains of Trichophyton rubrum (a dermatophyte causing chronic skin infections with high rates of drug resistance) found that eugenol inhibited the growth of 50% of T. rubrum strains at an MIC of 256 μg/ml, caused abnormalities in hyphae and decreased conidiogenesis, and exerted antifungal effects on the cell wall and cell membrane, acting on the cell membrane via inhibition of ergosterol biosynthesis, with the lower ergosterol content interfering with membrane integrity and functionality.

Against Candida species, an investigation of eugenol's antifungal potential using broth microdilution found MIC values of 400–800 µg/mL for Candida tropicalis and 200–400 µg/mL for Candida krusei; synergistic effects of eugenol and voriconazole were observed for Candida tropicalis (83.3%) and Candida krusei (77.7%), with no antagonistic activity.

Evidence strength (antimicrobial): Mostly in vitro / preclinical. A mechanistic viewpoint has been well described, and the evidence base in food preservation contexts is robust. Clinical data in humans for systemic or topical antimicrobial applications (outside of dentistry) is limited.

4.4 Anticancer Activity

Eugenol is reported to possess anticancer activity against various cancers, and the molecular mechanism of eugenol-induced apoptosis in melanoma, osteosarcoma, leukemia, gastric, skin tumors, and mast cells has been documented.

At the cellular level, in a leukemia cell line study, for the HL-60 cell line, the IC₅₀ of eugenol was 14.1 µM, with high gene expression of pro-apoptotic biomarkers (Caspase-3 and Caspase-9); Hoechst staining showed prominent apoptotic bodies leading to nuclear fragmentations, and eugenol proved to possess robust pro-apoptotic potential against the leukemia HL-60 cell line.

A 2025 review of eugenol's anticancer perspective reported that eugenol, a volatile phenolic bioactive compound with the formula C₁₀H₁₂O₂, has been reported with anticancer, antidiabetic, cardio- and pulmonary-protective roles. However, a critical systematic review of animal model studies noted that the major portion of animal trials fall into unclear and high-risk groups; the review emphasizes the importance of carrying out animal intervention research in animal-ethics-maintained laboratory conditions before translating in vivo experiments into human clinical studies. Furthermore, there is no report on anticancer formulations of eugenol approved for clinical use.

Evidence strength (anticancer): Predominantly in vitro and animal model data. No human clinical trials for cancer treatment have been completed or published. Current evidence is considered hypothesis-generating only.

4.5 Antidiabetic and Metabolic Effects

Research into eugenol's effects on glucose metabolism and diabetes has been conducted primarily in animal models. A study of eugenol's protective role against type 1 diabetes-induced oxidative stress showed that eugenol supplementation activated Nrf2, upregulated NQO-1 and HO-1, mitigated β-cell damage, and reduced oxidative stress-linked cell apoptosis. Another animal study by Jiang et al. (2022) studying the antidiabetic effect of eugenol in high-fat diet/streptomycin-induced diabetic mice showed that eugenol increased GLUT4 translocation and AMPK phosphorylation in skeletal muscles, increased intracellular Ca²⁺ levels via TRPV1, and activated CaMKK2; overall, eugenol was found efficient against high-fat-induced diabetes in this model.

Evidence strength (antidiabetic): Preclinical animal and in vitro data only. No human randomized controlled trials exist demonstrating glycemic or metabolic benefit from eugenol supplementation.

4.6 Cardiovascular Effects

Emerging preclinical research has investigated eugenol's potential cardiovascular applications. A 2023 cell-based study found that histone active mark H3K27ac was significantly reduced in cardiomyocytes exposed to ischemic conditions, and in a high-throughput drug screening assay of an antioxidant compound library comprising 84 drugs, eugenol was among the phenolic compounds found to play a crucial role in epigenetic modulation under ischemic stress. A study on vascular smooth muscle cells explored eugenol's effect in the context of atherosclerosis-related signaling; however, this work remained at the cell-biology level.

Evidence strength (cardiovascular): Early-stage preclinical data. No human clinical trials for cardiovascular endpoints have been reported.

5. Body Systems and Health Areas Associated with Eugenol

Based on the peer-reviewed literature, eugenol has been studied in relation to the following body systems and health areas:

Oral and dental system: Local analgesia, temporary dental obturation, alveolar osteitis prevention, endodontic sealing, antibacterial action against oral pathogens.
Immune and inflammatory system: Modulation of NF-κB, COX-2, and 5-LOX pathways; inhibition of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6).
Antioxidant / cellular protection: Activation of the Nrf2-ARE pathway, upregulation of SOD, CAT, GSH, GPx, GST.
Microbiology / infectious diseases: Antibacterial, antifungal (including Candida and Trichophyton), and antiviral (HSV-1/2 in vitro) activity.
Neurological / pain pathways: Voltage-gated sodium channel inhibition, TRPV1 modulation (agonism followed by desensitization).
Oncology (preclinical only): Pro-apoptotic effects in melanoma, leukemia, osteosarcoma, gastric, and skin cancer cell lines.
Metabolic / endocrine system (preclinical only): AMPK pathway activation, GLUT4 translocation, Nrf2-mediated pancreatic β-cell protection in animal models.
Cardiovascular system (preclinical only): Epigenetic modulation in ischemic cardiomyocytes; anti-proliferative effects on vascular smooth muscle cells.
Food safety / preservation: Biofilm inhibition, broad-spectrum antimicrobial activity against food-borne pathogens.

6. Dosage Forms and Dosages Reported in Studies

Dosage information for eugenol varies considerably depending on the application context. The following figures are drawn directly from regulatory and published scientific sources:

Safe daily intake (regulatory): The Joint FAO/WHO Expert Committee on Food Additives sets the safe daily limit for eugenol at 2.5 milligrams per kilogram of body weight; for a 150-pound person, that is approximately 170 milligrams per day. This is consistent with the figure noted in peer-reviewed reviews: a dose of 2.5 mg/kg body weight is regarded as safe.
No-observed-adverse-effect level (NOAEL) in regulatory toxicology: No adverse effects were observed up to the highest dose tested (300 mg/kg/day), with one eugenol study setting a NOAEL of 300 mg/kg/day and a lowest-observed-adverse-effect level (LOAEL) of 625 mg/kg/day based on decreased body weight. These are animal study values used for regulatory hazard assessment.
Antimicrobial (in vitro MIC values): The MIC against bacteria was 1000 µg/mL for eugenol in one comparative study. Against T. rubrum, eugenol inhibited the growth of 50% of strains at an MIC of 256 μg/mL.
Dental ZOE formulations: Eugenol is employed in clinical dental formulations (zinc oxide–eugenol pastes and sealers) at standardized concentrations as defined by manufacturers and regulatory standards; specific weight ratios vary by product and are not reducible to a single "dose."
Topical/transdermal (experimental): Research on transdermal eugenol administration for pain has used eugenol embedded in nanoparticle carriers; however, standardized clinical topical dosages for this route have not yet been established in completed trials.

Note: No large-scale human clinical trials have established therapeutic oral or systemic dosing regimens for eugenol as a supplement for non-dental indications.

7. Safety Considerations and Interactions

Regulatory Status

Eugenol is approved by the U.S. Food and Drug Administration (FDA) for use as a food additive and is generally recognized as safe (GRAS) by the FDA under 21 CFR 184.1257. Eugenol has been classified as a generally accepted safe chemical substance by the World Health Organization (WHO). Eugenol has been acknowledged as GRAS by the WHO and recognized as nonmutagenic. As such, eugenol has long been part of the normal human diet.

Concentration-Dependent Toxicity

Due to its known antibacterial, antiviral, antifungal, anticancer, anti-inflammatory and antioxidant properties, eugenol has long been used in various areas, but high concentrations can be toxic. Problems arise at much higher doses; in animal studies, the lethal dose ranges from about 1,190 to 3,000 mg per kilogram of body weight depending on species. Accidental high-dose exposure in humans has been linked to liver damage, lung irritation, and nervous system effects, though these cases are rare and involve amounts far beyond what anyone would get from food or normal product use.

The toxic mechanism at high doses involves reactive intermediates: eugenol has neurotoxic and hepatotoxic effects at high doses, and reactive quinone intermediates formed by its phenolic hydroxyl metabolism trigger oxidative stress and mitochondrial dysfunction; long-term intake at high levels may lead to irreversible neurological and liver damage.

In dental contexts specifically, eugenol released from zinc oxide eugenol (ZOE)-based sealants may cause irritation to the periapical tissues and has cytotoxic potential. At low concentrations, eugenol works as a mild anti-inflammatory and local anesthetic; however, higher concentrations are directly toxic to living tissue, and if pure eugenol contacts exposed pulp (the soft interior of the tooth), it can cause extensive tissue damage.

Hepatotoxicity Risk with Concentrated Forms

The danger with eugenol is concentrated forms — mainly clove essential oil, which is 60–90% eugenol by weight. At normal dietary doses, eugenol has never been shown to cause elevated liver enzymes or clinically apparent liver injury in humans; the toxicity risk is specific to concentrated oil ingestion. High doses of eugenol may cause damage to the liver.

Skin Sensitization and Allergic Contact Dermatitis

The more common concern at normal use levels is allergic reactions, particularly among dental professionals who handle eugenol-containing materials daily. Allergic contact dermatitis is a main concern; eugenol is one of the 26 fragrance allergens that must be listed on cosmetic labels in the European Union, and skin patch testing identifies it as a sensitizer in a small percentage of the population.

The sensitization mechanism involves oxidative metabolism: although eugenol is itself a weak sensitizer, it is oxidized to the highly reactive orthoquinone; the reactive hapten binds to proteins in the skin (haptens often have an affinity to electrons and bind covalently with amine and sulfhydryl groups on proteins), modifying the protein which, when exposed to the immune system, elicits an immune reaction.

Inhalation and Mucosal Irritation

Inhalation of eugenol can lead to bronchial irritation, dizziness, and rapid and shallow breathing. Concentrated eugenol or undiluted clove oil can irritate or burn skin and mucous membranes on contact.

Ingestion of Undiluted Clove Oil

As little as 5 to 10 milliliters of undiluted clove oil can cause seizures, coma, and liver failure, particularly in children. Swallowing large quantities of concentrated eugenol can cause nausea, vomiting, and in extreme cases, liver damage.

Pharmacokinetics

After oral intake, eugenol is rapidly absorbed and metabolized in the liver; approximately 95% of the dose is recovered in urine, with nearly all of it appearing within 24 hours.

Methyleugenol Distinction

It is important to distinguish eugenol from its closely related structural analogue methyleugenol. Methyleugenol has been shown to induce tumors of the bile duct, kidney, mesothelium, mammary gland, and skin in treated rats; in NTP studies on mice, increases in the incidences of liver neoplasms were observed in higher-dosed groups. Positive results on DNA adduct formation in the liver of both rats and humans, as well as in vivo genotoxicity testing, suggest that genotoxicity is an important mechanism in the carcinogenicity of methyleugenol. Eugenol itself has been recognized as nonmutagenic and is clearly distinguished from methyleugenol in regulatory and toxicological assessments.

References

Health Conditions

Health conditions that Eugenol may help support.

Bad Breath (Halitosis)Scientific
Eugenol, the principal active in clove oil, is a well-characterized antimicrobial used in clinical dentistry. It inhibits VSC-producing oral pathogens and is an active ingredient in commercial antiseptic mouthwashes including Listerine. A systematic review of essential oils for halitosis confirmed eugenol-containing oils exert documented antimicrobial effects against halitogenic bacteria. It is listed by systematic reviews and dental pharmacology sources among effective oral antiseptic agents.
ToothacheScientific
Eugenol is the primary bioactive constituent of clove oil and a foundational compound in professional dental analgesia. It inhibits voltage-gated sodium channels and prostaglandin synthesis, providing direct local anesthesia to dental pulp nociceptors. A landmark 2006 RCT demonstrated equivalence to benzocaine 20% for topical pre-injection anesthesia. It remains a standard ingredient in dental cements and root canal medicaments used clinically for toothache and pulpitis.

Body Systems

Body systems that Eugenol may help support.

No body systems available.