Herb reference

Clove

Syzygium aromaticum (L.) Merr. & L.M. Perry

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Botanical / editorial

Family: Myrtaceae
Plant type: evergreen tree
Route: Mixed route
Evidence tier: Mixed evidence

Maluku Islands (Spice Islands), Indonesia2000+Myrtaceae

Botanical / meta

Botanical identity

Botanical description

The clove tree is a symmetrical evergreen reaching 8–20 m in height, with large, opposite, glossy, lanceolate leaves that are aromatic when crushed. Fragrant clusters of tiny, pale pink to crimson flowers with yellow centres are borne terminally. The spice "clove" is the unopened, dried flower bud — a nail-shaped structure with a rounded head and tapered stem, turning from pale green to deep reddish-brown upon drying. Clove buds are harvested by hand before the flowers open and are sun-dried or heat-dried until dark brown and hard.

Pharmacognosy intro

Clove buds contain 14–21% volatile oil, of which eugenol constitutes 70–90% — the highest natural concentration of this phenylpropanoid of any plant. Other oil constituents include eugenyl acetate (8–15%) and β-caryophyllene (5–12%). Non-volatile fractions include tannins (8%), oleanolic acid, triterpenoids, and flavonoids (kaempferol, quercetin, and their glycosides). The stem and leaf oils have similar but less refined compositions. Eugenol is responsible for clove's anaesthetic, antimicrobial, anti-inflammatory, and antiplatelet properties. The high eugenol content makes clove oil both powerfully therapeutic and potentially toxic at high doses. Clove essential oil has demonstrated broad-spectrum antimicrobial activity against bacteria, fungi, and viruses in vitro.

Editorial orientation

The practical read

Body-first read

What it is for

Route panel

Preparation shapes the claim

Evidence and safety may differ by preparation. Essential oil, tea, tincture, extract, infused oil, and topical use are not interchangeable.

Mixed route

Quality

Fresh, dried, oil, and garden read

Growing tips

Clove trees require a tropical maritime climate with high humidity, consistent rainfall, and temperatures between 20–30°C. They thrive in rich, well-drained volcanic soils at elevations up to 600 m. Trees begin flowering at 5–7 years of age and can produce commercially for over 50 years. Buds are hand-harvested when pink but before opening, requiring skilled labour. Clove cultivation is limited to tropical regions; the tree cannot tolerate temperatures below 10°C.

Quality notes

Whole clove buds should be oily, dark reddish-brown, and strongly aromatic with a sweet-spicy, penetrating scent. Quality is assessed by the eugenol content — premium cloves contain 15–21% volatile oil with eugenol at 70–90%. The buds should float vertically in water (the "float test"), indicating high oil content. Ground clove loses volatile oils rapidly and should be used within 3–6 months. Clove essential oil should be dark amber, very viscous, and have a powerful warm-spicy aroma. Store in airtight, dark glass containers away from heat. Distinguish from clove stems (thicker, less aromatic) and clove leaves (longer, flatter) which are inferior products sometimes used to adulterate whole cloves.

Companion

Crystal pairing reference

Crystal side

Companion crystal

The deeper layer

Compound and clinical layer

Clinical and compound notes are included as a research layer, not as treatment instructions.

Safety intro

Clove is GRAS as a culinary spice. However, the essential oil requires significant caution: ingestion of more than 5 mL of clove oil can cause severe toxicity including nausea, vomiting, abdominal pain, CNS depression, convulsions, liver injury, and metabolic acidosis. Clove oil is cytotoxic to human fibroblasts and endothelial cells at concentrations as low as 0.03% (v/v). Eugenol has documented hepatotoxic potential at high doses — acute overdose can cause hepatic necrosis resembling acetaminophen toxicity. Eugenol inhibits platelet aggregation; individuals on anticoagulant or antiplatelet medications should avoid medicinal doses. The EMA has noted that available genotoxicity and carcinogenicity data on eugenol are "inconsistent and equivocal," though short-term local use at therapeutic concentrations appears to carry low risk. Eugenol can cause contact dermatitis, mucosal irritation, and allergic reactions in sensitive individuals. Clove oil should never be applied undiluted to skin or mucous membranes. Avoid essential oil use in infants and young children. Avoid medicinal doses during pregnancy and lactation.

Questions

Frequently asked about Clove

What are the critical safety warnings and drug interactions for clove?

Whole clove (Syzygium aromaticum) is GRAS as a culinary spice, but the essential oil demands serious caution because of its extreme eugenol concentration. Ingesting more than about 5 mL of clove oil can cause severe toxicity including vomiting, abdominal pain, CNS depression, convulsions, metabolic acidosis, and liver injury; eugenol has documented hepatotoxic potential and acute overdose can produce hepatic necrosis resembling acetaminophen toxicity. Clove oil is cytotoxic to human fibroblasts and endothelial cells at concentrations as low as 0.03 percent. Eugenol inhibits platelet aggregation, so people on anticoagulant or antiplatelet medications should avoid medicinal doses. The oil should never be applied undiluted to skin or mucous membranes, must be kept away from infants and young children, and medicinal doses should be avoided in pregnancy and lactation.

How is clove prepared and dosed, especially for dental use?

Whole or ground cloves are used as a spice to taste, while the essential oil is the medicinal form and must always be heavily diluted. For the traditional dental application, a drop of clove oil diluted in a carrier oil is applied to a carrier such as a cotton ball and held against an aching tooth, where eugenol provides temporary local anaesthesia and antimicrobial action; this is a stopgap, not a substitute for dental care. Concentrations matter because the oil is cytotoxic even at low percentages, so undiluted application to gums or mucosa is unsafe. Never swallow clove oil, and keep total exposure low given the 5 mL toxicity threshold. Powdered clove loses volatile oil quickly once ground, so whole buds give the most reliable potency.

How do you evaluate clove quality?

Quality whole cloves should be plump, dark reddish-brown, and oily enough to leave a faint mark or float upright when dropped in water; cloves that sink horizontally or are pale, shrivelled, and brittle have lost volatile oil. The bud should still have its round ball-shaped head intact, since headless stems indicate older or lower-grade material. Aroma is the quickest test: a strong, warm, sharply sweet scent signals high eugenol content, while a weak smell means depletion. For the essential oil, bud oil is more refined than the harsher stem and leaf oils, which have similar but coarser compositions. Pre-ground clove is the most degraded form and should be bought in small quantities.

Why does clove contain so much eugenol, and what does that mean in practice?

Clove buds contain 14 to 21 percent volatile oil, of which eugenol makes up 70 to 90 percent, the highest natural concentration of this phenylpropanoid of any plant, alongside eugenyl acetate and beta-caryophyllene. Eugenol is the molecule behind clove's anaesthetic, antimicrobial, anti-inflammatory, and antiplatelet properties, and it has demonstrated broad-spectrum antimicrobial activity against bacteria, fungi, and viruses in vitro. This same concentration is exactly what makes clove oil both powerfully therapeutic and genuinely hazardous: the dose that numbs a tooth is close in character to the dose that injures the liver. Understanding clove means understanding that its virtue and its danger are the same compound. That is why dilution and restraint define every safe use of the oil.

How should clove be stored and what is its shelf life?

Whole cloves are remarkably durable, retaining strong aroma and eugenol content for one to two years or more when kept in an airtight container away from light, heat, and moisture. Ground clove degrades far faster, losing much of its volatile oil within a few months, so buying whole and grinding as needed preserves potency. The essential oil is comparatively stable and lasts two to four years in dark glass kept cool, though oxidation gradually increases irritancy. Store the oil well out of reach of children given its toxicity. When whole cloves no longer release a sharp warm scent on being crushed, the eugenol-rich oil has significantly diminished.

Sources & Citations

Where this entry can be checked

Peer-reviewed sources for the pharmacological and clinical claims on this page. Crystalis herb entries describe tradition and current research; they are reference, not medical advice.

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SCI
Clove Essential Oil (Syzygium aromaticum L. Myrtaceae): Extraction, Chemical Composition, Food Applications, and Essential Bioactivity for Human Health
Haro-González JN, et al. (2021). Clove Essential Oil (Syzygium aromaticum L. Myrtaceae): Extraction, Chemical Composition, Food Applications, and Essential Bioactivity for Human Health. Molecules. [SCI]DOI 10.3390/molecules26216387

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