Tea Tree Oil
Scientific Name(s): Melaleuca alternifolia Cheel. Family: Myrtaceae
Common Name(s): Tea tree oil , melaleuca oil
Despite an abundance of commercial preparations promoted for antimicrobial use, sound clinical trials are limited. Trials have been conducted in conditions including nail infections, athlete's foot, fungal skin infections, acne, and methicillin-resistant Staphylococcus aureus . Case reports exist for use in other conditions.
Decolonization of methicillin-resistant S. aureus : Tea tree oil as a nasal cream (4% to 10%) applied 3 times a day for 5 days and 5% body wash for 5 days. Acne vulgaris: 5% tea tree oil gel applied for 20 minutes twice daily, then washed off. Onchomycosis (fungal nail infections): 100% tea tree oil applied for 6 months. Tinea pedis (athlete's foot): 25% to 50% tea tree oil for 4 weeks.
Oral ingestion is contraindicated.
Information regarding safety and efficacy in pregnancy and lactation is lacking.
None well documented.
Case reports exist of dermatitis associated with topical tea tree oil.
Tea tree oil is toxic when ingested orally. Some case studies of accidental and intentional poisoning exist; however, no deaths have been reported to the American Association of Poison Control Centers through 2006. Mutagenicity of tea tree oil appears to be low; however, chemical constituents have been shown to be cytotoxic and embryotoxic.
There are many plants known as tea trees, but the species M. alternifolia is the source of tea tree essential oil. Native to Australia coastal areas, the tea tree is an evergreen shrub that grows from 5 to 8 m in height. Its narrow, 4 cm, needle-like leaves release a distinctive aroma when crushed. The fruits grow in clusters, and its white flowers bloom in the summer. Ornamental Leptospermum species are distinct and are not the source of tea tree oil. Related species include Melaleuca quinquenervia (Cav.) S.T. Blake ( Melaleuca viridiflora sol.), a New Caledonian evergreen tree that yields niaouli oil, Melaleuca leucaden L., and Melaleuca cajuputi Powell (synonym, Melaleuca minor Sm.), which is the source of oil of cajuput that contains similar chemical constituents. 1 , 2
The indigenous people of Australia have used tea tree oil from crushed leaves as a traditional remedy for coughs and colds, as well as to treat wounds and skin conditions. Tea tree oil was first used in surgery and dentistry in the mid-1920s. Its healing properties were also used during World War II for skin injuries in munitions factory workers. Tea tree oil's popularity has resurfaced within the last few years as interest in natural therapies evolves, and it can be found in soaps, shampoos, and lotions. 2 , 3
The essential oil is normally obtained by steam distillation of the leaves and terminal branchlets, resulting in a transparent, colorless to pale yellow oil with a characteristic odor. The main constituent in tea tree's essential oil and present in concentrations of 30% or more is terpinen-4-ol, with more than 100 other constituents identified. The International Standards Organization requires 15 of these chemicals to be present, and concentrations of terpinen-4-ol must be at least 30% and 1,8-cineole (controversially considered a skin irritant) must be less than 15%. However, essential oils from other related species ( Melaleuca dissitiflora and Melaleuca linariifolia ) can also meet these same standards and have been used as adulterants. Other constituents include terpinene, terpinolene, pinene, cymene, and limonene. The composition of the essential oil may change with storage conditions, because heat, light, air, and moisture can affect the oil. 2 , 3 , 4
Uses and PharmacologyAntibacterial
In vitro studies have confirmed bactericidal and bacteriostatic (at lower concentrations) action of tea tree oil. A broad spectrum of bacterial pathogens are affected, including common skin Staphylococcus species, Enterococcus faecalis , and Pseudomonas aeruginosa , and most are susceptible to concentrations of 1% or less of tea tree essential oil; however, the minimum inhibitory concentration (MIC) of some pathogens is as high as 8%. The activity has been attributed mainly to terpineol content, but some studies suggest that cineole has a role. 2 , 5 , 6 , 7Animal data
A limited number of dermatological studies have been conducted in animals, particularly for chronic itching and fleas in dogs, but toxicity associated with ingesting the oil via licking limits therapeutic applications. 2 , 3 , 8 , 9Clinical data
Despite the large number of in vitro studies reported, few quality clinical trials have been conducted. Clinical studies have been conducted in acne, methicillin-resistant S. aureus , and gingivitis. Case reports exist for use in bacterial vaginitis. 10
One small trial established 5% tea tree oil to be more effective than placebo over 45 days in treating mild to moderate acne vulgaris. 11 A second trial demonstrated equivalence with benzoyl peroxide 5% over 3 months of treatment; however, it may have been insufficiently powered to detect a difference. 12
In studies evaluating tea tree oil in the decolonization of methicillin-resistant Staphylococcus aureus nasal application of ointment (4% to 10%) and body wash (5%), no difference was shown versus mupirocin 2% and chlorhexidine or triclosan. 13 , 14 In subgroup analysis of data from the larger trial, mupirocin nasal ointment performed better than 10% tea tree oil in nasal decolonization, while tea tree oil performed better than chlorhexidine in decolonizing the skin and skin lesions. 14 The results of a multicenter, open-label, randomized clinical trial on the effect of 5% tea tree oil wash in preventing methicillin-resistant S. aureus colonization in patients in the intensive care unit are forthcoming. 15
A wide range of yeasts, dermatophytes, and other filamentous fungi were susceptible to varying concentrations of tea tree oil. Reported MICs range from 0.12% to 2%, but some species (eg, Aspergillus niger ) require higher concentrations of up to 8%. It has been suggested that different phases of fungal growth are affected differently by tea tree oil. 2 , 3 , 10 , 18 , 19Clinical data
Despite an abundance of commercial preparations promoted for antifungal use, clinical trials of sound methodology are limited. Trials have been conducted in conditions including nail infections (onchomycosis), tinea pedis and versicolor, dandruff, and oral candidiasis, along with case reports of other fungal conditions.
Equivalence was found for 100% tea tree oil and clotrimazole 1% in treating onchomycosis over 6 months in one study. 20 However, a study evaluating butenafine with tea tree oil versus tea tree oil alone in treating fungal toenail infections found no effect for tea tree oil alone (the placebo arm of the study) applied over 8 weeks. 21
Tea tree oil (25% and 50%) was better than placebo in treating tinea pedis (athlete's foot) in one clinical trial. 22 A second trial found 10% tea tree oil to be no better than placebo in attaining a negative culture, but equivalent to tolnaftate 1% as assessed by reduction of symptoms. 23 The popularity of tea tree oil in treating tinea pedis is attributed to the reduction of scaling, itching, and burning symptoms. 8
A 5% tea tree oil shampoo used for 4 weeks was shown to be effective in treating dandruff, 24 and in an open-label study with no control arm, tea tree oil resolved oral candidial lesions in some, but not all, patients who were positive for HIV. 25Antiviral
Early studies examined the antiviral action of tea tree oil on tobacco mosaic virus, while in vitro studies in human viruses have been limited mainly to the herpes simplex viruses. 2 , 3 At 2.5 mcg/mL, tea tree oil suppressed herpes simplex virus type 1 in an in vitro study examining various oils. 26 A small pilot study found some benefit in using a 6% tea tree oil gel in the treatment of recurrent herpes labialis over placebo; however, statistical significance was not achieved. 27Other effects
Anti-inflammatory action has been described for tea tree oil and may account for observed clinical response of reduced itching. In histamine studies and nickel-induced contact hypersensitivity tests, tea tree oil reduced flare and erythema at higher concentrations (40% to 100%). 2 , 8 , 28 , 29
DosageDecolonization of methicillin-resistant Staphylococcus aureus
100% tea tree oil applied for 6 months. 20Tinea pedis (athlete's foot)
Information regarding safety and efficacy in pregnancy and lactation is lacking. Alpha-terpinene, present in tea tree oil, was embryotoxic in rats. 9
None well documented.
Case reports describe the irritant effect of topical tea tree oil and contact dermatitis. 3 , 9 , 33 The irritant effect of tea tree oil, often attributed to the cineole constituent, has been disputed because 1,8-cineole concentrations of up to 28% have not produced reactions. 2 , 9
Internal doses of 10 to 70 mL have resulted in ataxia and decreasing levels of consciousness. Activated charcoal and sorbitol have been used as an antidote in cases of poisoning in children. No ongoing neurological sequelae have been reported. 9
Reports of cytotoxicity experienced with tea tree oil vary, and mutagenicity is likewise unclear but appears to be low based on experimental data. 9 , 26 Ototoxicity has been evaluated in guinea pigs, and strengths of 2% or less are considered safe for use. 9
Bibliography1. Melaleuca alternifolia Cheel. USDA, NRCS. 2010. The PLANTS Database ( http://plants.usda.gov , January 2010). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.
2. Carson CF, Hammer KA, Riley TV. Melaleuca alternifolia (tea tree) oil: a review of antimicrobial and other medicinal properties. Clin Microbiol Rev . 2006;19(1):50-62.
3. Crawford GH, Sciacca JR, James WD. Tea tree oil: cutaneous effects of the extracted oil of Melaleuca alternifolia . Dermatitis . 2004;15(2):59-66.
4. International Organization for Standardization. Oil of Melaleuca , terpinen-4-ol type (Tea Tree oil). ISO 4730:2004. Geneva, Switzerland. http://www.iso.org/iso/catalogue_detail.htm?csnumber=37033 .
5. Carson CF, Riley TV. Antimicrobial activity of the major components of the essential oil of Melaleuca alternifolia . J Appl Bacteriol . 1995;78(3):264-269.
6. Carson CF, Hammer KA, Riley TV. Broth micro-dilution method for determining the susceptibility of Escherichia coli and Staphylococcus aureus to the essential oil of Melaleuca alternifolia (tea tree oil). Microbios . 1995;82(332):181-185.
7. Raman A, Weir U, Bloomfield SF. Antimicrobial effects of tea-tree oil and its major components on Staphylococcus aureus , Staph. epidermidis and Propionibacterium acnes . Lett Appl Microbiol . 1995;21(4):242-245.
8. Bergstrom KG. Tea tree oil: panacea or placebo? J Drugs Dermatol . 2009;8(5):494-496.
9. Hammer KA, Carson CF, Riley TV, Nielsen JB. A review of the toxicity of Melaleuca alternifolia (tea tree) oil. Food Chem Toxicol . 2006;44(5):616-625.
10. Van Kessel K, Assefi N, Marrazzo J, Eckert L. Common complementary and alternative therapies for yeast vaginitis and bacterial vaginosis: a systematic review. Obstet Gynecol Surv . 2003;58(5):351-358.
11. Enshaieh S, Jooya A, Siadat AH, Iraji F. The efficacy of 5% topical tea tree oil gel in mild to moderate acne vulgaris: a randomized, double-blind placebo-controlled study. Indian J Dermatol Venereol Leprol . 2007;73(1):22-25.
12. Martin KW, Ernst E. Herbal medicines for treatment of bacterial infections: a review of controlled clinical trials. J Antimicrob Chemother . 2003;51(2):241-246.
13. Caelli M, Porteous J, Carson CF, Heller R, Riley TV. Tea tree oil as an alternative topical decolonization agent for methicillin-resistant Staphylococcus aureus . J Hosp Infect . 2000;46(3):236-237.
14. Dryden MS, Dailly S, Crouch M. A randomized, controlled trial of tea tree topical preparations versus a standard topical regimen for the clearance of MRSA colonization. J Hosp Infect . 2004;56(4):283-286.
15. Thompson G, Blackwood B, McMullan R, et al. A randomized controlled trial of tea tree oil (5%) body wash versus standard body wash to prevent colonization with methicillin-resistant Staphylococcus aureus (MRSA) in critically ill adults: research protocol. BMC Infect Dis . 2008;8:161.
16. Soukoulis S, Hirsch R. The effects of a tea tree oil-containing gel on plaque and chronic gingivitis. Aust Dent J . 2004;49(2):78-83.
17. Arweiler NB, Donos N, Netuschil L, Reich E, Sculean A. Clinical and antibacterial effect of tea tree oil—a pilot study. Clin Oral Investig . 2000;4(2):70-73.
18. Hammer KA, Carson CF, Riley TV. In vitro activities of ketoconazole, econazole, miconazole, and Melaleuca alternifolia (tea tree) oil against Malassezia species. Antimicrob Agents Chemother . 2000;44(2):467-469.
19. Bagg J, Jackson MS, Petrina Sweeney M, Ramage G, Davies AN. Susceptibility to Melaleuca alternifolia (tea tree) oil of yeasts isolated from the mouths of patients with advanced cancer. Oral Oncol . 2006;42(5):487-492.
20. Buck DS, Nidorf DM, Addino JG. Comparison of two topical preparations for the treatment of onychomycosis: Melaleuca alternifolia (tea tree) oil and clotrimazole. J Fam Pract . 1994;38(6):601-605.
21. Syed TA, Qureshi ZA, Ali SM, Ahmad S, Ahmad SA. Treatment of toenail onchomycosis with 2% butenafine and 5% Melaleuca alternifolia (tea tree) oil in cream. Trop Med Int Health . 1999;4(4):284-287.
22. Satchell AC, Saurajen A, Bell C, Barnetson RS. Treatment of interdigital tinea pedis with 25% and 50% tea tree oil solution: a randomized, placebo-controlled, blinded study. Australas J Dermatol . 2002;43(3):175-178.
23. Tong MM, Altman PM, Barnetson RS. Tea tree oil in the treatment of tinea pedis. Australas J Dermatol . 1992;33(3):145-149.
24. Satchell AC, Saurajen A, Bell C, Barnetson RS. Treatment of dandruff with 5% tea tree oil shampoo. J Am Acad Dermatol . 2002;47(6):852-855.
25. Vazquez JA, Zawawi AA. Efficacy of alcohol-based and alcohol-free melaleuca oral solution for the treatment of fluconazole-refractory oropharyngeal candidiasis in patients with AIDS. HIV Clin Trials . 2002;3(5):379-385.
26. Astani A, Reichling J, Schnitzler P. Comparative study on the antiviral activity of selected monoterpenes derived from essential oils. Phytother Res . 2010;24(5):673-679.
27. Carson CF, Ashton L, Dry L, Smith DW, Riley TV. Melaleuca alternifolia (tea tree) oil gel (6%) for the treatment of recurrent herpes labialis. J Antimicrob Chemother . 2001;48(3):450-451.
28. Khalil Z, Pearce AL, Satkunanathan N, Storer E, Finlay-Jones JJ, Hart PH. Regulation of wheal and flare by tea tree oil: complementary human and rodent studies. J Invest Dermatol . 2004;123(4):683-690.
29. Pearce AL, Finlay-Jones JJ, Hart PH. Reduction of nickel-induced contact hypersensitivity reactions by topical tea tree oil in humans. Inflamm Res . 2005;54(1):22-30.
30. Greay SJ, Ireland DJ, Kissick HT, et al. Induction of necrosis and cell cycle arrest in murine cancer cell lines by Melaleuca alternifolia (tea tree) oil and terpinen-4-ol. Cancer Chemother Pharmacol . 2010;65(5):877-888.
31. Gray SG, Clair AA. Influence of aromatherapy on medication administration to residential-care residents with dementia and behavioral challenges. Am J Alzheimers Dis Other Demen . 2002;17(3):169-174.
32. Sadr Lahijani MS, Raoof Kateb HR, Heady R, Yazdani D. The effect of German chamomile ( Marticaria recutita L.) extract and tea tree ( Melaleuca alternifolia L.) oil used as irrigants on removal of smear layer: a scanning electron microscopy study. Int Endod J . 2006;39(3):190-195.
33. Halcón L, Milkus K. Staphylococcus aureus and wounds: a review of tea tree oil as a promising antimicrobial. Am J Infect Control . 2004;32(7):402-408.
34. Bronstein AC, Spyker DA, Cantilena LR Jr, Green J, Rumack BH, Heard SE. 2006 Annual Report of the American Association of Poison Control Centers' National Poison Data System (NPDS). Clin Toxicol (Phila) . 2007;45(8):815-917.
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