Clove

Clove (Syzygium aromaticum) is the dried, unopened flower bud of a tropical evergreen tree in the myrtle family (Myrtaceae), native to the Maluku Islands in eastern Indonesia. The buds are harvested by hand before the flowers open and sun-dried until dark brown. Eugenol makes up about seventy to ninety percent of their essential oil; other important constituents include eugenyl acetate and beta-caryophyllene. Eugenol shapes the intense, sweet-spicy aroma and contributes to local anaesthetic effects.

The EMA Committee on Herbal Medicinal Products (HMPC) has a traditional-use monograph for clove oil, Caryophylli floris aetheroleum, for minor mouth and throat inflammation and temporary relief of toothache due to a cavity. For the whole bud, Caryophylli flos, it issued a public statement rather than a monograph. The German Commission E monograph is titled Caryophylli flos. The oral and dental uses attributed to Commission E in the EMA report concern clove oil. Alqareer and colleagues studied clove gel for needle insertion pain in 2006. Shan and colleagues found high antioxidant capacity for clove extract in the TEAC laboratory assay in 2005. This does not establish a corresponding effect in humans. At Christianes Naturkraft, clove is a spice ingredient in Klassik syrup, rooted in the Christmas tradition of mulled wine and gingerbread.

The history of clove is closely tied to the international spice trade. An often-told story about chewing cloves before audiences at the Chinese imperial court cannot be used here as a securely dated record. Asian trade routes carried the spice far beyond its native Maluku Islands. Portuguese and later Dutch ships reached the islands in the sixteenth century. During the seventeenth and eighteenth centuries, the Dutch East India Company enforced its clove monopoly through violence and destroyed trees outside controlled growing areas. The name Nelke refers to the nail shape of the bud, as does English clove, but the two words have different linguistic origins.

In the Austrian and broader German-speaking tradition, clove is first and foremost a Christmas spice. Whole cloves stuck into oranges make the classic Weihnachts-Pomander. Glühwein on the Christkindlmarkt is unthinkable without clove, cinnamon, and orange peel. Lebkuchen, Magenbrot, and the wider Weihnachtsbäckerei rely on ground clove for the deep, warm note that signals winter. The Apothekentradition runs in parallel: Nelkenöl as a topical Zahnschmerzen remedy is a classic of European household medicine, and the EMA HMPCEuropean Medicines Agency, Committee on Herbal Medicinal Products (HMPC) traditional-use monograph for clove oil (Caryophylli floris aetheroleum) formally recognises the traditional use for minor oral mucosa inflammation and temporary relief of toothache due to a cavity, while the German Commission E monograph is titled Caryophylli flos. The oral and dental uses attributed to Commission E in the EMA report also concern the oil. The plant therefore arrives in Austria along two routes that share the same chemistry: the culinary one through the Glühwein pot and the Lebkuchen tin, and the medicinal one through the pharmacy shelf.

Eugenol is the principal chemical constituent of clove and makes up about seventy to ninety percent of the essential oil from its buds. Other major components are eugenyl acetate and beta-caryophyllene. In laboratory studies, eugenol affects several ion channels, including TRPV1, which also responds to capsaicin and heat. Its local anaesthetic effect cannot, however, be explained by this receptor alone. Laboratory and animal studies also show effects on inflammatory pathways such as COX-2 and NF-κB, reviewed by Barboza and colleagues in 2018.

In experimental studies, beta-caryophyllene acts as an agonist at the CB2 cannabinoid receptor. It also occurs in other culinary spices; this does not establish a particular benefit of clove in humans. Antiplatelet effects of eugenol have also been described in the laboratory. They do not establish a clinically relevant interaction during short-term local use of clove oil; the EMA monograph lists no reported interactions. Traditional digestive uses of the spice should also be distinguished from these experimental findings.

In 2006, Alqareer and colleagues studied the topical anaesthetic effect of clove gel in a randomised trial involving 73 healthy adults. Clove gel and twenty percent benzocaine gel were each compared with placebo on the opposite side of the mouth. Both active gels reduced needle insertion pain compared with placebo; no statistically significant difference was found between them. Four participants developed small aphthous-like ulcers after clove gel application. The result does not establish formal equivalence and addresses neither cavity-related toothache nor effects after eating cloves. The EMA monograph for clove oil instead rests on long-standing use for minor mouth and throat inflammation and temporary relief of cavity-related toothache. Toothache requires dental assessment as soon as possible.

For digestive uses, the rationale for clove comes mainly from tradition; many other effects have so far been studied in the laboratory. Shan and colleagues compared twenty-six spice extracts using the TEAC assay in 2005. Clove extract was among the samples with high antioxidant capacity. Such a chemical measurement does not establish a health benefit in humans. Chaieb and colleagues reviewed laboratory findings on the antimicrobial activity of clove oil and eugenol in 2007. This does not establish similar effects from ordinary culinary amounts in humans. The 2018 review by Barboza and colleagues describes effects of eugenol on COX-2 and NF-κB, among other pathways, in cell and animal models. It likewise does not demonstrate a clinical effect of culinary amounts.

Forms and preparation

For culinary use, whole cloves are the standard form. Two to four cloves go into a litre of mulled wine or Glühwein together with cinnamon, orange peel, and star anise, simmered gently for ten to twenty minutes and strained before serving. One or two cloves can be added to a chai or to a pot of black tea. Ground cloves are the form most often used in Lebkuchen, Spekulatius, and the broader Weihnachtsbäckerei spice mix; the amount depends on the recipe. For a traditional clove tea, one or two crushed cloves steeped in a cup of freshly boiled water for five to ten minutes is the household preparation. The EMA monograph covers preparations containing clove oil. A chewed bud or homemade clove tea is not equivalent. For a mouthwash or targeted dental application, use a suitable preparation with clear instructions. Do not drip clove oil onto the gums or swallow it. Temporary toothache relief does not replace dental treatment.

Dosage

In cooking, the amount depends on the recipe and taste: whole cloves flavour punch or compote, while ground cloves are used in Christmas baking. Even small amounts have an intense flavour. This does not provide a dose for clove oil. The EMA distinguishes mouthwashes from targeted dental use at different concentrations. Use a medicinal product intended for the purpose according to its leaflet and seek advice from a pharmacist or dentist. Start sparingly when seasoning and adjust to taste. Clove oil for toothache relief is only a temporary measure; see a dentist as soon as possible. Worsening or persistent mouth and throat complaints also need professional assessment. The EMA limits both uses to no more than one week. Follow the product age limits and warnings.

1. Athbi Alqareer; Asma Alyahya; Lars Andersson. The effect of clove and benzocaine versus placebo as topical anesthetics. 2006. doi:10.1016/j.jdent.2006.01.009
2. Bin Shan; Yizhong Z. Cai; Mei Sun; Harold Corke. Antioxidant capacity of 26 spice extracts and characterization of their phenolic constituents. 2005. doi:10.1021/jf051513y
3. Kamel Chaieb; Hafedh Hajlaoui; Tarek Zmantar; Amel Ben Kahla-Nakbi; Mahmoud Rouabhia; Kacem Mahdouani; Amina Bakhrouf. The chemical composition and biological activity of clove essential oil, Eugenia caryophyllata (Syzigium aromaticum L. Myrtaceae): a short review. 2007. doi:10.1002/ptr.2124
4. Joice Nascimento Barboza; Carlos da Silva Maia Bezerra Filho; Renan Oliveira Silva; Jand Venes R. Medeiros; Damião Pergentino de Sousa. An Overview on the Anti-inflammatory Potential and Antioxidant Profile of Eugenol. 2018. doi:10.1155/2018/3957262
5. European Medicines Agency, Committee on Herbal Medicinal Products (HMPC). Community herbal monograph on Syzygium aromaticum (L.) Merill et L. M. Perry, floris aetheroleum. 2011. Source
6. Jürg Gertsch; Marco Leonti; Stefan Raduner; Ildiko Racz; Jian-Zhong Chen; Xiang-Qun Xie; Karl-Heinz Altmann; Meliha Karsak; Andreas Zimmer. Beta-caryophyllene is a dietary cannabinoid. 2008. doi:10.1073/pnas.0803601105
7. C.-K. Park; H. Y. Li; K.-Y. Yeon; S. J. Jung; S.-Y. Choi; S. J. Lee; S. Lee; K. Park; J. S. Kim; S. B. Oh. Eugenol inhibits sodium currents in dental afferent neurons. 2006. doi:10.1177/154405910608501005