When we think of this fragrant spice, we usually see it as studded artfully in a beautifully baked ham or flavoring a delicious cup of spiced tea. While food products comprise the largest and most well-known uses of cloves, its use in folk medicine is older and more established. The small, dark brown, odd-shaped spice that we know is the dried flower bud of the clove tree, or Syzygium aromaticum. In contrast to the tiny half-inch structure of its dried flower bud, the clove tree grows as tall as 12 meters with large leaves and reddish flowers.1 The trees can live to be 100 years old.
For medicinal purposes, cloves are used in either whole or expressed oil forms. Harvested mostly in Indonesia, cloves are a huge cash crop industry for the country, accounting for nearly one quarter of a billion dollars annually in exports.2 Cloves have been prized for their properties for centuries, with the spice being found in vessels of the Roman Empire dating back to over 1,700 BC. When Magellan’s ships returned from their circumnavigation of the world, one of the ships was carrying a cargo of cloves. At that time, cloves were more valuable than gold due to their lack of availability and wide range of use.
The main compound found in cloves that is believed to be responsible for most of its medicinal action is the essential oil eugenol.2 Eugenol is a phenolic compound and a potent anti-inflammatory, as well as antimicrobial agent. Clove oil is categorized as ‘Generally Recognized to be Safe’ in oral doses up to 2.5 mg/kg in humans.3
Probably the most exciting use of clove oil is as an antimicrobial. This action has been studied extensively as it applies to oral health. Growing attention is being paid to the role of oral health in overall health and well-being. In the United States alone, tooth decay remains the most common chronic disease of school-aged children and up to 90% of adults.4 With the high cost of professional dental care, self-care agents are increasingly attractive.
The main bacterium causing gingivitis and tooth decay is Streptococcus mutans.5 In an in-vitro study of various essential oils including clove against erythromycin as a positive control, clove oil inhibited the growth of S mutans as well as the adherence of the bacteria to the gingival and tooth surfaces.5
Researchers have found that the main mechanism of action of clove oil is cell membrane damage, which results in cell death and lack of proliferation.6 With the known inhibitory action on S mutans, clove oil has also been studied for its antibacterial effect on other enteropathogens. In another in-vitro study comparing clove extract’s action with chloramphenicol and ampicillin against four common enteropathogens, clove oil was up to 70% as effective at preventing growth of these pathogens as the positive control ampicillin.6,7
Another more traditional use of clove oil is for pain relief. Holding a clove seed in the mouth next to an aching tooth is an age-old home remedy. The mechanism of action for pain relief appears to be linked to the activation of calcium and chloride channels in ganglion cells.8 Additional research indicates inhibition of prostaglandin synthesis, cyclooxygenase, and lipoxygenase, which are all known to increase pain perception.9
Other very early in-vitro studies indicate promising anti-mutagenic action of clove oil. In a laboratory animal study examining clove oil’s effect on melanoma growth, treatment showed a very significant retardation of tumor growth, as well as an almost 40% reduction in actual tumor size.10 In an impressive endpoint, 50% of the animals in the control group died from the disease but none of the animals treated with clove oil showed any metastatic invasion of the tumor cells.10
How supplied, dose, cost
Cloves may be purchased in a wide variety of forms. The intended use typically drives the form chosen. The whole spice and the essential oil are the most common forms and can be found in grocery or health food stores. The cost is minimal, at usually $5 or less. As a topical treatment for pain, especially in the oral cavity, one to five drops of essential oil on a small piece of gauze or cotton as needed is usually sufficient.9
Safety, interactions, side effects
As with any essential oil, there may be allergic reactions. Careful skin patch testing should be performed if topical use is planned. For oral use, due to the highly aromatic nature of clove oil, bronchospasm has been noted, along with tissue irritation.9
There are no known interactions. However, due to its anti-inflammatory activity, the oil should be used with caution in conjunction with any other medication that possesses prostaglandin inhibitory action.
Whether as a tasty addition to a recipe or a quick remedy for a toothache, there appears to be no downside to the use of clove oil or spice. In underserved healthcare areas, addition of daily oral rinses with clove oil mouthwash may improve dental health and help prevent the known health problems associated with gum disease and dental caries. Future studies examining the potential in fighting certain malignant conditions are ongoing. Recommending the use of cloves for patients should be considered safe and helpful when added to current health regimens.
- Clove characteristics. Botanical-online website. http://www.botanical-online.com/english/clove.htm. Accessed November 14, 2016.
- Agrawal M, Agrawal S, Rastogi R, Singh P, Adyanthaya BR, Gupta HL. A review on uses of clove in oral and general health. Indian Journal of Research in Pharmacy and Biotechnology. 2014;2(4):1321-1324.
- Gülçin I, Elmastaş M, Aboul-Enein HY. Antioxidant activity of clove oil—a powerful antioxidant source. Arab J Chem. 2012;5(4):489-499.
- Hygiene-related diseases: dental caries (tooth decay). Centers for Disease Control and Prevention website. http://www.cdc.gov/healthywater/hygiene/disease/dental_caries.html. Updated September 22, 2016. Accessed November 14, 2016.
- Chaiya A, Saraya S, Chuakul W, Temsiririrkkul R. Screening for dental caries: Preventive activities of medicinal plants against Streptococcus mutans. Mahidol University Journal of Pharmaceutical Sciences. 2013;40(1):9-17.
- Dua A, Garg G, Nagar S, Mahajan R. Methanol extract of clove (Syzygium aromaticum Linn.) damages cells and inhibits growth of enteropathogens. J Innov Biol. 2014;1(4):200-205.
- Shah A, Jani M, Shah H, Chaudhary N, Shah A. Antimicrobial effect of clove oil (Luang) extract on Enterococcus faecalis. Journal of Advanced Oral Research. 2014;5(3):36-38.
- Li HY, Lee BK, Kim JS, Jung SJ, Oh SB. Eugenol inhibits ATP—induced P2X currents in trigeminal ganglion neurons. Korean J Physiol Pharmacol. 2008;12(6):315-321.
- Skidmore-Roth L. Mosby’s Handbook of Herbs & Natural Supplements. 3rd ed. St. Louis, MO: Elsevier Health Sciences; 2005.
- Ghosh R, Nadiminty N, Fitzpatrick JE, Alworth WL, Slaga TJ, Kumar AP. Eugenol causes melanoma growth suppression through inhibition of E2F1 transcriptional activity. J Biol Chem. 2005;280(7):5812-5819.