Origin of this essential oil, the tea tree, Melaleuca alternifolia.
Tea tree plantation, Coraki, New South Wales.

Tea tree oil, also known as melaleuca oil, is an essential oil with a fresh camphoraceous odor and a colour that ranges from pale yellow to nearly colourless and clear.[1] It is derived from the leaves of the tea tree, Melaleuca alternifolia, native to southeast Queensland and the northeast coast of New South Wales, Australia. The oil comprises many constituent chemicals and its composition changes if it is exposed to air and oxidizes.

Commercial use of tea tree oil began in the 1920s, pioneered by the entrepreneur Arthur Penfold. As of 2017 the global tea tree oil market was valued at US$39 million.[2]

As a traditional medicine, it is typically used as a topical medication in low concentrations for the attempted treatments of skin conditions, but there is little evidence of efficacy.[3][4][5] Tea tree oil is claimed as useful for treating dandruff, acne, lice, herpes, insect bites, scabies, and skin fungal or bacterial infections.[4][5][6] However, there is not enough evidence to support any of these claims due to the limited amount of research conducted on the topic.[4][7] Tea tree oil is neither a patented product nor an approved drug in the United States,[5] although it is approved as a complementary medicine for aromatherapy in Australia.[8] It is poisonous if consumed by mouth, and unsafe to use on children.[9]

Uses[edit]

Tea tree oil has been used as a traditional herbal medicine in the belief it treats acne, nail fungus, or athlete's foot, with little evidence to support these uses.[4][10][11] A 2015 Cochrane systematic review for acne complementary therapies, found a low-quality single trial showed benefit compared to placebo.[12]

According to the Committee on Herbal Medicinal Products (CHMP) of the European Medicines Agency, traditional usage suggests that tea tree oil is a plausible treatment for "small superficial wounds, insect bites and small boils", that it may help reduce itching in minor cases of athlete's foot, and help with mild inflammation of the mouth lining.[13] The CHMP say tea tree oil products should not be used on people under 12 years of age.

Tea tree oil is not recommended for treating nail fungus, as it is not effective.[14] It is not recommended for treating head lice in children because its effectiveness and safety has not been established and it could cause skin irritation or allergic reactions.[15][16]

Safety[edit]

Tea tree oil is poisonous when taken internally.[4][7] It may cause drowsiness, confusion, hallucinations, coma, unsteadiness, weakness, vomiting, diarrhea, nausea, blood cell abnormalities, and severe rashes. It should be kept away from pets and children.[7] Tea tree oil should not be used in or around the mouth.[4][9]

Application of tea tree oil to the skin can cause an allergic reaction. Tea tree oil has caused more documented allergic reactions than any other form of essential oil. The potential for causing an allergic reaction increases as the oil ages and its chemical composition changes.[17] Adverse effects include skin irritation, allergic contact dermatitis, systemic contact dermatitis, linear immunoglobulin A disease, erythema multiforme-like reactions, and systemic hypersensitivity reactions.[6][18] Allergic reactions may be due to the various oxidation products that are formed by exposure of the oil to light and/or air.[18][19] Consequently, oxidized tea tree oil should not be used.[20]

In Australia tea tree oil is one of the many essential oils that have been increasingly causing cases of poisoning, mostly of children. In the period 2014-2018 there were 749 reported cases in New South Wales, accounting for 17% of essential oil poisoning incidents.[21]

Hormonal effects[edit]

Tea tree oil potentially poses a risk for causing abnormal breast enlargement in men.[22][23] A 2018 study by the National Institute of Environmental Health Sciences found four of the constituent chemicals (eucalyptol, 4-terpineol, dipentene and alpha-terpineol) are endocrine disruptors, raising concerns of potential environmental health impact from the oil.[24]

Toxicity in animals[edit]

In dogs and cats, death[25][26] or transient signs of toxicity (lasting 2 to 3 days), such as lethargy, weakness, in coordination and muscle tremors, have been reported after external application at high doses.[27]

As a test of toxicity by oral intake, the median lethal dose (LD50) in rats is 1.9–2.4 ml/kg.[28]

Composition and characteristics[edit]

Tea tree oil composition,
as per ISO 4730 (2017)[1]
Component Concentration
terpinen-4-ol 35.0–48.0%
γ-terpinene 14–28%
α-terpinene 6.0–12.0%
1,8-cineole traces–10.0%
terpinolene 1.5–5.0%
α-terpineol 2.0–5.0%
α-pinene 1.0–4.0%
p-Cymene 0.5–8.0%
Sabinene traces–3.5%
limonene 0.5–1.5%
aromadendrene 0.2–3.0%
ledene 0.1–3.0%
globulol traces–1.0%
viridiflorol traces–1.0%

Tea tree oil is defined by the International Standard ISO 4730 ("Oil of Melaleuca, terpinen-4-ol type"), containing terpinen-4-ol, γ-terpinene, and α-terpinene as about 70% to 90% of whole oil, while p-cymene, terpinolene, α-terpineol, and α-pinene collectively account for some 15% of the oil (table, right).[1][3][5] The oil has been described as colorless to pale yellow[1] having a fresh, camphor-like smell.[29]

Tea tree oil products contain various phytochemicals among which terpinen-4-ol is the major component.[1][3] Adverse reactions diminish with lower eucalyptol content.[6]

History and extraction[edit]

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 antiseptic properties.[28]

Tea tree oil was first extracted from Melaleuca alternifolia in Australia, and this species remains the most important commercially. In the 1970s and 1980s, commercial plantations began to produce large quantities of tea tree oil from Melaleuca alternifolia. Many of these plantations are located in New South Wales.[28] Since the 1970s and 80s, the industry has expanded to include several other species 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.[30] Whereas the availability and nonproprietary nature of tea tree oil would make it – if proved effective – particularly well-suited to a disease like scabies that affects poor people disproportionately, those same characteristics diminish corporate interest in its development and validation.[5]

According to Allied Market Research, "the global tea tree oil market size was valued at $38.8 million in 2017 and is projected to reach $59.5 million by 2025".[2]

Research directions[edit]

Tea tree oil is under investigation to see whether it might help in controlling Demodex mites and associated rosacea. As of 2018 no clinical trials had been conducted.[31]

See also[edit]

References[edit]

  1. ^ a b c d e "Essential oil of Melaleuca, terpene-4-ol (tea tree oil): ISO 4730: 2017 (E)". International Organization for Standardization (ISO), Geneva, Switzerland. 2017. Retrieved 2 February 2019.
  2. ^ a b "Tea Tree Oil Market Outlook – 2025". Allied Market Research. May 2019.
  3. ^ a b c "Opinion on Tea tree oil" (PDF). SCCP/1155/08 Scientific Committee on Consumer Products. 16 December 2008.
  4. ^ a b c d e f "Tea tree oil". National Center for Complementary and Integrative Health, US National Institutes of Health. 2011-11-09. Retrieved 30 May 2016.
  5. ^ a b c d e Thomas, J; Carson, C. F; Peterson, G. M; Walton, S. F; Hammer, K. A; Naunton, M; Davey, R. C; Spelman, T; Dettwiller, P; Kyle, G; Cooper, G. M; Baby, K. E (2016). "Therapeutic Potential of Tea Tree Oil for Scabies". The American Journal of Tropical Medicine and Hygiene (Review). 94 (2): 258–266. doi:10.4269/ajtmh.14-0515. PMC 4751955. PMID 26787146.
  6. ^ a b c 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.
  7. ^ a b c 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.
  8. ^ "Summary for ARTG Entry: 79370 TEA TREE OIL PURE ESSENTIAL OIL". Therapeutic Goods Administration. 2020. Retrieved 3 July 2020.
  9. ^ a b "Tea Tree Oil". National Capital Poison Center. Retrieved 4 December 2013.
  10. ^ "Fungal skin infection - foot" (Clinical Knowledge Summary). UK National Institute for Health and Care Excellence. 2014. Retrieved 16 January 2017.
  11. ^ "Tea tree oil". Mayo Foundation for Medical Education and Research, Mayo Clinic. 2017. Retrieved 2 December 2017.
  12. ^ Cao H, Yang G, Wang Y, Liu JP, Smith CA, Luo H, Liu Y (January 2015). "Complementary therapies for acne vulgaris". Cochrane Database Syst Rev (Systematic Review). 1: CD009436. doi:10.1002/14651858.CD009436.pub2. PMC 4486007. PMID 25597924.
  13. ^ "Melaleucae aetheroleum". Committee on Herbal Medicinal Products. 24 November 2014.
  14. ^ Halteh P, Scher RK, Lipner SR (2016). "Over-the-counter and natural remedies for onychomycosis: do they really work?". Cutis. 98 (5): E16–E25. PMID 28040821.CS1 maint: multiple names: authors list (link)
  15. ^ "Head lice and nits". National Health Service. 10 January 2018.
  16. ^ 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.
  17. ^ de Groot AC, Schmidt E (2016). "Tea tree oil: contact allergy and chemical composition". Contact Dermatitis (Review). 75 (3): 129–43. doi:10.1111/cod.12591. PMID 27173437.
  18. ^ a b 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.
  19. ^ Aberer, W (January 2008). "Contact allergy and medicinal herbs". Journal der Deutschen Dermatologischen Gesellschaft. 6 (1): 15–24. doi:10.1111/j.1610-0387.2007.06425.x. PMID 17919303.
  20. ^ "The Effectiveness and Safety of Australian Tea Tree Oil". Australian Government - Rural Industries and Development Corporation. Archived from the original on November 1, 2018. Retrieved 26 February 2014.
  21. ^ Lee KA, Harnett JE, Cairns R (2019). "Essential oil exposures in Australia: analysis of cases reported to the NSW Poisons Information Centre". Medical Journal of Australia. doi:10.5694/mja2.50403. ISSN 0025-729X. PMID 31709543. Lay summary.
  22. ^ "Breast enlargement in males". Medline Plus. US National Library of Medicine. Retrieved 15 November 2015.
  23. ^ "Gynecomastia". Endocrine Society. May 2018.
  24. ^ "Chemicals in lavender and tea tree oil appear to be hormone disruptors". Endocrine Society. 19 March 2018.
  25. ^ "Tea Tree Oil and Dogs, Tea Tree Oil and Cats". Petpoisonhelpline.com. Retrieved December 13, 2012.
  26. ^ "Tea Tree Oil Toxicity". Veterinarywatch. Archived from the original on January 11, 2013. Retrieved December 13, 2012.
  27. ^ 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.
  28. ^ a b c 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 1360273. PMID 16418522.
  29. ^ Billee Sharp (18 September 2013). Lemons and Lavender: The Eco Guide to Better Homekeeping. Cleis Press. pp. 43–. ISBN 978-1-936740-11-6.
  30. ^ 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.
  31. ^ Lam NS, Long XX, Griffin RC, Chen MK, Doery JC (October 2018). "Can the tea tree oil (Australian native plant: Melaleuca alternifolia Cheel) be an alternative treatment for human demodicosis on skin?". Parasitology (Review). 145 (12): 1510–1520. doi:10.1017/S0031182018000495. PMID 29667560.