Chemistry:Tea tree oil

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Short description: Essential oil derived from leaves


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][2] 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.[3]

As a traditional medicine, it is typically used as a topical medication in low concentrations for the treatment of skin conditions, but little evidence exists of clinical efficacy.[2][4][5][6]

Tea tree oil is neither a patented product nor an approved drug in the United States,[2][6] although it is approved as a complementary medicine for aromatherapy in Australia.[7] It is poisonous if consumed by mouth and is unsafe for children.[8]

Uses

Although tea tree oil is claimed to be useful for treating dandruff, acne, lice, herpes, insect bites, scabies, and skin fungal or bacterial infections,[6][9] insufficient evidence exists to support any of these claims due to the limited quality of research.[2][5][10] A 2015 Cochrane review of acne complementary therapies found a single low-quality trial showing benefit on skin lesions compared to placebo.[11]

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

Tea tree oil is not recommended for treating nail fungus because it is yet to be proven effective,[13] It is not recommended for treating head lice in children because its effectiveness and safety have not been established and it could cause skin irritation or allergic reactions.[14][15] There is no good evidence tea tree oil is an effective treatment for demodex mite infestations.[16]

Toxicity

Tea tree oil is highly toxic when ingested orally.[2][5][17][10] 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.[10] It should not be used in or around the mouth.[2][5][8]

Application of tea tree oil to the skin can cause an allergic reaction,[2] the potential for which increases as the oil ages and its chemical composition changes.[18] Adverse effects include skin irritation, allergic contact dermatitis, systemic contact dermatitis, linear immunoglobulin A disease, erythema multiforme-like reactions, and systemic hypersensitivity reactions.[9][19] Allergic reactions may be due to the various oxidation products that are formed by exposure of the oil to light and air.[19][20] Consequently, oxidized tea tree oil should not be used.[21]

In Australia, tea tree oil is one of the many essential oils causing poisoning, mostly of children. From 2014 to 2018, 749 cases were reported in New South Wales, accounting for 17% of essential oil poisoning incidents.[22]

Hormonal effects

Tea tree oil potentially poses a risk for causing abnormal breast enlargement in men[23][24] and prepubertal children.[25][26] 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.[27]

In animals

In dogs and cats, death[28][29] or transient signs of toxicity (lasting two to three days), such as lethargy, weakness, incoordination, and muscle tremors, have been reported after external application at high doses.[30]

As a test of toxicity by oral intake, the median lethal dose (LD50) in rats is 1.9–2.4 ml/kg.[31]

Composition and characteristics

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).[1][4][6] The oil has been described as colorless to pale yellow[1][2] having a fresh, camphor-like smell.[32]

Tea tree oil products contain various phytochemicals, among which terpinen-4-ol is the major component.[1][2][4] Adverse reactions diminish with lower eucalyptol content.[9]

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.[33]

The commercial tea tree oil industry originated in the 1920s when Australian chemist Arthur Penfold investigated the business potential of a number of native extracted oils; he reported that tea tree oil had promise, as it exhibited antiseptic properties.[31]

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 M. alternifolia. Many of these plantations are located in New South Wales.[31] 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 (considered an invasive species in Florida[34]).

Similar oils can also be produced by water distillation from Melaleuca linariifolia and Melaleuca dissitiflora.[35] Whereas the availability and nonproprietary nature of tea tree oil would make it – if proved effective – particularly well-suited to a disease such as scabies that affects poor people disproportionately, those same characteristics diminish corporate interest in its development and validation.[6]

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".[3]

See also

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 "Essential oil of Melaleuca, terpene-4-ol (tea tree oil): ISO 4730: 2017 (E)". International Organization for Standardization (ISO), Geneva, Switzerland. 2017. https://www.sis.se/api/document/preview/921469. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 "Tea tree oil". Drugs.com. 13 February 2023. https://www.drugs.com/npp/tea-tree-oil.html. 
  3. ↑ 3.0 3.1 "Tea Tree Oil Market Outlook – 2025". Allied Market Research. May 2019. https://www.alliedmarketresearch.com/tea-tree-oil-market. 
  4. ↑ 4.0 4.1 4.2 "Opinion on Tea tree oil". SCCP/1155/08 Scientific Committee on Consumer Products. 16 December 2008. http://ec.europa.eu/health/ph_risk/committees/04_sccp/docs/sccp_o_160.pdf. 
  5. ↑ 5.0 5.1 5.2 5.3 "Tea tree oil". National Center for Complementary and Integrative Health, US National Institutes of Health. 1 October 2020. https://nccih.nih.gov/health/tea/treeoil.htm. 
  6. ↑ 6.0 6.1 6.2 6.3 6.4 Thomas, J; Carson, C. F; Peterson, G. M et al. (2016). "Therapeutic Potential of Tea Tree Oil for Scabies". The American Journal of Tropical Medicine and Hygiene 94 (2): 258–266. doi:10.4269/ajtmh.14-0515. PMID 26787146. 
  7. ↑ "Summary for ARTG Entry: 79370 Tea Tree Oil, Pure Essential Oil". Therapeutic Goods Administration. 2020. https://www.ebs.tga.gov.au/servlet/xmlmillr6?dbid=ebs/PublicHTML/pdfStore.nsf&docid=79370&agid=(PrintDetailsPublic)&actionid=1. 
  8. ↑ 8.0 8.1 "Tea Tree Oil". National Capital Poison Center. http://www.poison.org/poisonpost/winter2010/teatreeoil.htm. 
  9. ↑ 9.0 9.1 9.2 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. 
  10. ↑ 10.0 10.1 10.2 "Tea Tree Oil". American Cancer Society Complete Guide to Complementary and Alternative Cancer Therapies (2nd ed.). American Cancer Society. 2009. ISBN 9780944235713. https://archive.org/details/americancancerso0000unse. 
  11. ↑ "Complementary therapies for acne vulgaris". Cochrane Database Syst Rev 1 (1): CD009436. January 2015. doi:10.1002/14651858.CD009436.pub2. PMID 25597924. 
  12. ↑ "Melaleucae aetheroleum". Committee on Herbal Medicinal Products. 24 November 2014. https://www.ema.europa.eu/en/medicines/herbal/melaleucae-aetheroleum. 
  13. ↑ "Over-the-counter and natural remedies for onychomycosis: do they really work?". Cutis 98 (5): E16–E25. 2016. PMID 28040821. 
  14. ↑ "Head lice and nits". National Health Service. 10 January 2018. https://www.nhs.uk/conditions/head-lice-and-nits/. 
  15. ↑ 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. 
  16. ↑ "Tea tree oil for Demodex blepharitis". Cochrane Database Syst Rev 6 (6): CD013333. June 2020. doi:10.1002/14651858.CD013333.pub2. PMID 32589270. 
  17. ↑ "Tea tree oil". PubChem, US National Library of Medicine. 30 October 2021. https://pubchem.ncbi.nlm.nih.gov/compound/22833361. 
  18. ↑ "Tea tree oil: contact allergy and chemical composition.". Contact Dermatitis 75 (3): 129–43. 2016. doi:10.1111/cod.12591. PMID 27173437. 
  19. ↑ 19.0 19.1 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. 
  20. ↑ 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. 
  21. ↑ "The Effectiveness and Safety of Australian Tea Tree Oil". Australian Government - Rural Industries and Development Corporation. https://rirdc.infoservices.com.au/downloads/07-143. 
  22. ↑ "Essential oil exposures in Australia: analysis of cases reported to the NSW Poisons Information Centre". Medical Journal of Australia 212 (3): 132–133. 2019. doi:10.5694/mja2.50403. ISSN 0025-729X. PMID 31709543. 
  23. ↑ "Breast enlargement in males". US National Library of Medicine. https://www.nlm.nih.gov/medlineplus/ency/article/003165.htm. 
  24. ↑ "Gynecomastia". Endocrine Society. May 2018. https://www.hormone.org/diseases-and-conditions/gynecomastia. 
  25. ↑ "Isoniazid-induced gynaecomastia: report of a paediatric case and review of literature". BMC Endocr Disord 20 (1): 160. October 2020. doi:10.1186/s12902-020-00639-9. PMID 33109161. 
  26. ↑ "Breast development in pediatric patients from birth to puberty: physiology, pathology and imaging correlation". Pediatr Radiol 51 (11): 1959–1969. October 2021. doi:10.1007/s00247-021-05099-4. PMID 34236480. 
  27. ↑ "Chemicals in lavender and tea tree oil appear to be hormone disruptors". Endocrine Society. 19 March 2018. https://www.endocrine.org/news-and-advocacy/news-room/2018/chemicals-in-lavender-and-tea-tree-oil-appear-to-be-hormone-disruptors. 
  28. ↑ "Tea Tree Oil and Dogs, Tea Tree Oil and Cats". Petpoisonhelpline.com. http://www.petpoisonhelpline.com/poison/tea-tree-oil/. 
  29. ↑ "Tea Tree Oil Toxicity". Veterinarywatch. http://www.veterinarywatch.com/Abstract-tea-tree-oil.htm. 
  30. ↑ 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. 
  31. ↑ 31.0 31.1 31.2 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. PMID 16418522. 
  32. ↑ Billee Sharp (18 September 2013). Lemons and Lavender: The Eco Guide to Better Homekeeping. Cleis Press. pp. 43–. ISBN 978-1-936740-11-6. https://books.google.com/books?id=v1MTKm49UqgC&pg=PT43. 
  33. ↑ "Melaleuca alternifolia". https://apps.cals.arizona.edu/arboretum/taxon.aspx?id=824. 
  34. ↑ "Melaleuca quinquenervia". https://plants.ifas.ufl.edu/plant-directory/melaleuca-quinquenervia/. 
  35. ↑ 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. 



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