Tea tree oil
Tea tree oil (TTO), or melaleuca oil, is an essential oil with a fresh camphoraceous odor and a colour that ranges from pale yellow to nearly colourless and clear. It is taken from the leaves of the Melaleuca alternifolia, which is native to Southeast Queensland and the Northeast coast of New South Wales, Australia.
Tea tree oil is toxic when taken by mouth, but is widely used in low concentrations in cosmetics and skin washes. Tea tree oil has been claimed to be useful for treating a wide variety of medical conditions. It shows some promise as an antimicrobial. Tea tree oil may be effective in a variety of dermatologic conditions, including dandruff, acne, lice, herpes, and other skin infections. However, the quality of the evidence is low.
Tee tree oil is not recommended for the treatment of athlete's foot.
Tee tree oil is not recommended for treating head lice in children because it could cause skin irritation or allergic reactions, because of contraindications, and because of a lack of knowledge about the oil's safety and effectiveness.
A 2006 review of the toxicity of tea tree oil concludes that it may be used externally in its diluted form by the majority of individuals without adverse effect (provided oxidization is avoided). Tea tree oil is poisonous when taken internally.
Tea tree oil is a commercially refined composition of several naturally occurring chemical compounds and is hazardous if misused. Available literature suggests that tea tree oil can be used topically in diluted form by the majority of individuals without adverse effects. Topical application of tea tree oil can cause adverse reactions at high concentration. Adverse effects including skin irritation, allergic contact dermatitis, systemic contact dermatitis, linear immunoglobulin A disease, erythema multiforme like reactions, and systemic hypersensitivity reactions.
Tea tree oil is toxic when swallowed. According to the American Cancer Society, ingesting tea tree oil has been reported to cause drowsiness, confusion, hallucinations, coma, unsteadiness, weakness, vomiting, diarrhea, stomach upset, blood cell abnormalities, and severe rashes. It should be kept away from pets and children. Tea tree oil should not be used in or around the mouth. There is at least one case of poisoning reported in medical literature.
Exposure of tea tree oil to air and light results in oxidation of some of its components. Oxidized tea tree oil should not be used. Some people experience allergic contact dermatitis as a reaction to dermal contact with tea tree oil. Allergic reactions may be due to the various oxidation products that are formed by exposure of the oil to light and/or air.
In vitro testing of tea tree oil shows that it contains chemicals which are weakly estrogenic, causing particular concern for use with children. However, in tests, the chemicals which show this effect failed to show absorption into the skin, and evidence of a hormonal effect is therefore considered implausible by an EU scientific committee.
In dogs and cats, death or transient signs of toxicity (lasting 2 to 3 days), such as depression, weakness, incoordination and muscle tremors, have been reported after external application at high doses. In rats the median lethal dose (LD50) is 1.9–2.4 ml/kg.
Undiluted tea tree oil can cause some hearing loss when used in the ears of non-human animals. However, a 2% concentration has not been shown to have any lasting effect. It is not known whether the same is true for humans.
Composition and characteristics
Tea tree oil is defined by the International Standard ISO 4730 ("Oil of Melaleuca, Terpinen-4-ol type"), which specifies levels of 15 components needed to define an oil as "tea tree oil." The oil has been described as having a fresh, camphor-like smell.
Tea tree oils come in six different chemical combinations: a terpinen-4-ol type, a terpinolene type, and four 1,8-cineole types. These various oil types contain over 98 compounds, with terpinen-4-ol the major component responsible for antimicrobial and anti-inflammatory properties. A second component 1,8-cineole, is likely responsible for most allergies in TTO products. Adverse reactions to TTO diminish with minimization of 1,8-cineole content. In commercial production, TTO is prepared as a terpinen-4-ol type.
History and extraction
The name tea tree is used for several plants, mostly from Australia and New Zealand, from the family Myrtaceae, related to the myrtle. The use of the name probably originated from Captain James Cook's description of one of these shrubs that he used to make an infusion, to drink in place of tea.
The commercial tea tree oil industry originated in the 1920s when Arthur Penfold, an Australian, investigated the business potential of a number of native extracted oils; he reported that tea tree oil had promise, as it exhibited powerful antiseptic properties.
Tea tree oil was first extracted from Melaleuca alternifolia in Australia, and this species remains the most important commercially. Several other species are cultivated for their extracted oil: Melaleuca armillaris and Melaleuca styphelioides in Tunisia and Egypt; Melaleuca leucadendra in Egypt, Malaysia and Vietnam; Melaleuca acuminata in Tunisia; Melaleuca ericifolia in Egypt; and Melaleuca quinquenervia in the United States. Similar oils can also be produced by water distillation from Melaleuca linariifolia and Melaleuca dissitiflora.
Studies using petri dishes originally suggested that tea tree oil kills methicillin-resistant Staphylococcus aureus (MRSA) in nasal or extra-nasal (topical) colonization studies, but, as of 2005, there appeared to be insufficient evidence to recommend it for use. A 2008 article from the American Cancer Society says that studies have previously suggested a possible role for the topical application of tea tree oil as an antiseptic, but that, "despite years of use, available clinical evidence does not support the effectiveness of tea tree oil for treating skin problems and infections in humans."
The National Center for Complementary and Integrative Health say there is tentative evidence for the use of tea-tree oil in additional-to-standard treatments of MRSA, but notes that the evidence is from small studies, and that there is no evidence involving humans. Other uses that have been researched include applications for nail fungus, dandruff, acne, and athlete's foot, but the evidence is of poor quality. Gingivitis is mentioned as another potential use.
A 2012 review of head lice treatment recommended against the use of tea tree oil on children because it could cause skin irritation or allergic reactions, because of contraindications, and because of a lack of knowledge about the oil's safety and effectiveness.
- Cajeput oil — derived from Melaleuca leucadendra
- [unreliable source?]"Directory of Essential Oils for Aromatherapy: Tea-Tree Oil (Melaleuca alternifolia)". Holistics Online.
- Russell J, Rovere A, eds. (2009). "Tea Tree Oil". American Cancer Society Complete Guide to Complementary and Alternative Cancer Therapies (2nd ed.). American Cancer Society. ISBN 9780944235713.
- "Tea Tree Oil". National Capital Poison Center. Retrieved 4 December 2013.
-  SCCP/1155/08 Scientific Committee on Consumer Products SCCP OPINION ON Tea tree oil – European Union Commission Health and Consumer Union protection director general – adopted 18th plenary of 16 December 2008
- Pazyar, N; Yaghoobi, R; Bagherani, N; Kazerouni, A (July 2013). "A review of applications of tea tree oil in dermatology". International Journal of Dermatology. 52 (7): 784–90. doi:10.1111/j.1365-4632.2012.05654.x. PMID 22998411.
- "Tea tree oil". National Center for Complementary and Integrative Health (NCCIH). Retrieved 30 May 2016.
- "Fungal skin infection - foot" (Clinical Knowledge Summary). National Institute for Health and Care Excellence. 2014. Retrieved 16 January 2017.
- "Fungal nail infection" (Clinical Knowledge Summary). National Institute for Health and Care Excellence. 2014. Retrieved 16 January 2017.
- Eisenhower, Christine; Farrington, Elizabeth Anne (2012). "Advancements in the Treatment of Head Lice in Pediatrics". Journal of Pediatric Health Care. 26 (6): 451–61; quiz 462–4. doi:10.1016/j.pedhc.2012.05.004. PMID 23099312.
- Hammer, KA; Carson, CF; Riley, TV; Nielsen, JB (May 2006). "A review of the toxicity of Melaleuca alternifolia (tea tree) oil.". Food and Chemical Toxicology. 44 (5): 616–25. doi:10.1016/j.fct.2005.09.001. PMID 16243420.
- Hammer, K; Carson, C; Riley, T; Nielsen, J (2006). "A review of the toxicity of Melaleuca alternifolia (tea tree) oil". Food and Chemical Toxicology. 44 (5): 616–25. doi:10.1016/j.fct.2005.09.001. PMID 16243420.
- "Ingestion of tea tree oil (Melaleucaoil) by a 4‐year‐old boy".
- "The Effectiveness and Safety of Australian Tea Tree Oil". Australian Government - Rural Industries and Development Corporation. Retrieved 26 February 2014.
- Aberer, W (January 2008). "Contact allergy and medicinal herbs". Journal der Deutschen Dermatologischen Gesellschaft = Journal of the German Society of Dermatology : JDDG. 6 (1): 15–24. doi:10.1111/j.1610-0387.2007.06425.x. PMID 17919303.
- "Tea Tree Oil and Dogs, Tea Tree Oil and Cats". Petpoisonhelpline.com. Retrieved December 13, 2012.
- "Tea Tree Oil Toxicity". Veterinarywatch. Retrieved December 13, 2012.
- Villar, D; Knight, MJ; Hansen, SR; Buck, WB (April 1994). "Toxicity of melaleuca oil and related essential oils applied topically on dogs and cats". Veterinary and human toxicology. 36 (2): 139–42. PMID 8197716.
- Carson CF, Hammer KA, Riley TV (January 2006). "Melaleuca alternifolia (Tea Tree) oil: a review of antimicrobial and other medicinal properties". Clin. Microbiol. Rev. 19: 50–62. doi:10.1128/CMR.19.1.50-62.2006. PMC . PMID 16418522.
- "Tea tree oil". Medline Plus, a service of the U.S. National Library of Medicine from the National Institutes of Health. 27 July 2012.
- Billee Sharp (18 September 2013). Lemons and Lavender: The Eco Guide to Better Homekeeping. Cleis Press. pp. 43–. ISBN 978-1-936740-11-6.
- Hart, P.H.; Brand, C.; Carson, C.F.; Riley, T.V.; Prager, R.H.; Finlay-Jones, J.J. (2000). "Terpinen-4-ol, the main component of the essential oil of Melaleuca alternifolia (tea tree oil), suppresses inflammatory mediator production by activated human monocytes.". Inflammation Research. 49 (11): 619–26. doi:10.1007/s000110050639. PMID 11131302.
- Carson, C. F.; Hammer, K. A.; Riley, T. V. (2006). "Melaleuca alternifolia (Tea Tree) Oil: A Review of Antimicrobial and Other Medicinal Properties". Clinical Microbiology Reviews. 19 (1): 50–62. doi:10.1128/CMR.19.1.50-62.2006. PMC . PMID 16418522.
- Sávia Perina Portilho Falci (July 2015). "Antimicrobial activity of Melaleuca sp. oil against clinical isolates of antibiotics resistant Staphylococcus aureus". Acta Cirurgica Brasileira. 30 (7): 401–6. doi:10.1590/S0102-865020150060000005. PMID 26108028.
- Flaxman, D.; Griffiths, P. (2005). "Is tea tree oil effective at eradicating MRSA colonization? A review". Br. J. Community Nurs. 10 (3, March): 123–126. PMID 15824699.
- Bradley, Suzanne F (January 2011). "MRSA colonisation (eradicating colonization in people without active/invasive infection)". Clinical Evidence. 2011. PMID 21477403.