Latin name: Syzygium aromaticum
Common names: Clove, Cloves
Synonyms: Caryophyllus aromaticus, Eugenia caryophyllata
A spice, which may result in allergy symptoms in sensitised individuals.
Cloves are native to the Moluccas (once known as the Spice Islands), but are now grown in other tropical areas throughout the world. Cloves are extremely aromatic, with up to 15% essential oil (70 to 85% eugenol), and so have long been prized for their intense fragrance and burning taste, as well as their medicinal properties. Trade between the ‘Clove island’ (Ternate) and China dates back at least 2 500 years. Archaeology suggests clove was known to the Egyptians, and it was evidently supplied to the Romans of the late Empire by Egyptian traders. During the seventeenth century, the Dutch had a virtual monopoly on the clove trade.
The clove tree is a slender evergreen, conical or cylindrical and up to 30 m tall. Roots are a dense mat close to the ground surface. The flowers, when allowed to develop, are red and white, or rose-peach in colour. ‘Cloves’ are the deep red-brown, dried flower buds, under a centimetre in length. The name ‘clove’ is derived from Latin clavus, or ‘nail’, because of its shape.
From Sri Lanka to North Africa, cloves are essential ingredients in ethnic cuisines, especially in meat and rice dishes. Cloves are less popular in Europe and America, but are traditional (particularly when combined with cinnamon) in some pastries and stewed fruits. They are also found in certain stews and pickles. The most common flavouring method in the West is to simmer whole cloves with fish, poultry, game and meat.
In Southeast Asia, however, cloves are seldom a flavouring for food. Both the clove (the flower bud) and the mother-of-clove (the fruit) have mainly medicinal and other non-food uses. Indonesia uses 50% of the world's production of cloves, almost exclusively in clove-flavoured cigarettes (kretek). These have become increasingly popular among US smokers, even though delivering more nicotine, carbon monoxide and tar than conventional cigarettes. (1) Clove may be added to other cigarettes as a taste enhancer.
In Ethiopia, coffee is often roasted together with cloves. Perhaps the most universal use of cloves is in spice mixtures, including curry paste and Mexican mole sauces. Worcestershire (or Worcester) sauce has a strong clove component.
Medicinal uses of cloves, though various, have centred on the treatment of digestive ailments (flatulence, diarrhoea and disorders of the liver, stomach and bowel), fungi and parasites. Their efficacy depends on the essential oil of clove, which can come from the spice, the bud or the leaf. The oil is widely used as an analgesic and antiseptic agent in dentistry, and so is often found in toothpaste and tooth powders. It flavours medicines and is a flavourant, scent or deodorant in a range of products, including perfumes, soaps and detergents.
No allergens from this plant have yet been characterised.
Cross-reactivity can be expected among the different species of the genus. (2)
Clove and allspice have often been reported to provoke allergic patch-test reactions in patients allergic to balsam of Peru, a phenomenon thought to be a result of these spices containing several of the same or related substances, e.g. cinnamic aldehyde, eugenol and vanillin. (3)
Anecdotal evidence suggests that clove may induce symptoms of food allergy in sensitised individuals; however, few studies have been reported to date. It is possible that the allergy occurs more frequently than has been reported. Tests for specific IgE assess immediate hypersensitivity reactions, and clove allergy has been infrequently reported.
According to the CICBAA data bank in France, in skin-specific IgE tests conducted for spice carried out in 589 patients with food allergy and suspected food allergy to spices, frequent sensitisation to Apiaceae was observed, in coriander, caraway, fennel and celery. No patients were found to be allergic to clove. (4)
However, in a study of Type VI delayed-hypersensitivity reactions to spice, clove caused the most reactions. Nine common spices were tested epicutaneously in 338 dermatological patients, 118 of whom were allergic to balsam of Peru; positive reactions to 1 or more spices were seen in 50 patients. The spices giving positive reactions most often were clove, Jamaica pepper and cinnamon (cassia). (3) Similarly, patch tests with a number of spices on 29 patients yielded the report that positive reactions to balsam of Peru were seen in 17 patients, and to clove, Jamaica pepper or cinnamon in 5. (5)
Of 1 000 patients investigated for occupational skin disease, 5 had hand (or finger) occupational allergic contact dermatitis from spices. The causative spices were garlic, cinnamon, ginger, allspice and clove. (6)
Clove and clove oil contain eugenol. An early survey indicated that, at the concentrations present in consumer products, eugenol alone or as part of clove leaf oil has a very low potential to elicit pre-existing sensitisation (‘elicited’ reactions) or to induce hypersensitivity (‘induced’ reactions). (7)
Nevertheless, a number of reports have indicated the allergic potential of clove oil or eugenol. Oral irritation, purpura of the lips and stomatitis with clove oil have been reported. (8)
Occupational allergic contact dermatitis from eugenol, oil of cinnamon and oil of cloves was described in a physiotherapist. (9) The frequency of responses to selected fragrance materials in 218 fragrance-sensitive subjects was evaluated in 8 centres worldwide, using a fragrance mixture and 17 less well-studied fragrance materials. Reaction to the fragrance mixture occurred in 76% of the subjects, and 93% of the reactions were to clove bud oil. (10)
The results of a study done on rats suggest that eugenol has anti-anaphylactic properties in preventing mast cell degranulation. (11)
Clove, present in an herbal product, was said to potentially increase the risk of bleeding or potentiate the effects of warfarin therapy. (12) Two antiplatelet components have been isolated and identified: eugenol and acetyl eugenol. They inhibited arachidonate-, adrenaline- and collagen-induced platelet aggregation. (13) Acetyl eugenol, a component of oil of cloves, was reported to inhibit aggregation of platelets and to alter arachidonic acid metabolism in human blood platelets. (14)
Health effects, including severe pulmonary toxicity, are suspected to be associated with clove cigarette (kretek) use among adolescents and young adults. The most likely candidate for a specific toxic effect, of the chemical constituents of kreteks, is eugenol. (15) Inhaling clove cigarette smoke has been associated with severe lung injury in a few susceptible individuals with prodromal respiratory infection. Some individuals with normal respiratory tracts appear to have suffered aspiration pneumonitis as the result of a diminished gag reflex, induced by a local anaesthetic action of eugenol, which is volatilised into the smoke. (16)
Compiled by Dr Harris Steinman.
- Malson JL, Lee EM, Murty R, Moolchan ET, Pickworth WB. Clove cigarette smoking: biochemical, physiological, and subjective effects. Pharmacol Biochem Behav 2003;74(3):739-45.
- Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09.
- Niinimaki A. Delayed-type allergy to spices. Contact Dermatitis 1984;11:34-40.
- Moneret-Vautrin DA, Morisset M, Lemerdy P, Croizier A, Kanny G. Food allergy and IgE sensitization caused by spices: CICBAA data (based on 589 cases of food allergy). Allerg Immunol (Paris) 2002;34(4):135-40.
- Niinimaki A. Double-blind placebo-controlled peroral challenges in patients with delayed-type allergy to balsam of Peru. Contact-Dermatitis. 1995;33(2):78-83.
- Kanerva L, Estlander T, Jolanki R. Occupational allergic contact dermatitis from spices. Contact Dermatitis 1996;35(3):157-62.
- Rothenstein AS, Booman KA, et al. Eugenol and clove leaf oil: a survey of consumer patch-test sensitization. Food Chem Toxicol 1983;21(6):727-33.
- Silvers SH. Stomatitis and dermatitis venanata with purpura, resulting from oil of cloves and oil of cassia. Dental Items of Interest 1939;61:649-51.
- Sanchez-Perez J, Garcia-Diez A. Occupational allergic contact dermatitis from eugenol, oil of cinnamon and oil of cloves in a physiotherapist. Contact Dermatitis 1999;41(6):346-7.
- Larsen W, Nakayama H, Fischer T, Elsner P, Frosch P, Burrows D, Jordan W, Shaw S, Wilkinson J, Marks J, Sugawara M, Nethercott M, Nethercott J. Fragrance contact dermatitis - a worldwide multicenter investigation (Part III). Contact Dermatitis 2002;46(3):141-4.
- Kim HM, Lee EH, Kim CY, Chung JG, Kim SH, Lim JP, Shin TY. Antianaphylactic properties of eugenol. Pharmacol Res. 1997;36(6):475-80.
- Heck AM, DeWitt BA, Lukes AL. Potential interactions between alternative therapies and warfarin. Am J Health Syst Pharm 2000;57(13):1221-7.
- Srivastava KC. Antiplatelet principles from a food spice clove (Syzygium aromaticum L) [corrected] Prostaglandins Leukot Essent Fatty Acids 1993;48(5):363-72.
- Srivastava KC, Malhotra N. Acetyl eugenol, a component of oil of cloves (Syzygium aromaticum L.) inhibits aggregation and alters arachidonic acid metabolism in human blood platelets. Prostaglandins Leukot Essent Fatty Acids 1991;42(1):73-81.
- Guidotti TL. Critique of available studies on the toxicology of kretek smoke and its constituents by routes of entry involving the respiratory tract. Arch-Toxicol. 1989;63(1):7-12.
- No authors listed. Evaluation of the health hazard of clove cigarettes. Council on Scientific Affairs. JAMA 1988;260(24):3641-4.