Tea tree oil

Although tea tree oil is claimed to be useful for treating dandruff, acne, lice, herpes, insect bites, scabies, and skin fungal or bacterial infections,{{cite journal |author1=Pazyar, N |author2=Yaghoobi, R |author3=Bagherani, N |author4= Kazerouni, A |title=A review of applications of tea tree oil in dermatology |journal=International Journal of Dermatology |date=July 2013 |volume=52 |issue=7 |pages=784–90 |pmid=22998411 |doi=10.1111/j.1365-4632.2012.05654.x|s2cid=2270233 }} insufficient evidence exists to support any of these claims due to the limited quality of research. A 2015 Cochrane review of acne complementary therapies found a single low-quality trial showing benefit on skin lesions compared to placebo.{{cite journal |vauthors=Cao H, Yang G, Wang Y, Liu JP, Smith CA, Luo H, Liu Y |title=Complementary therapies for acne vulgaris |journal=Cochrane Database Syst Rev |volume=1 |pages=CD009436 |date=January 2015 |issue=1 |pmid=25597924 |pmc=4486007 |doi=10.1002/14651858.CD009436.pub2 |type=Systematic Review}} Tea tree oil was also used during World War II to treat skin lesions of munitions factory workers.

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.{{cite web |publisher=Committee on Herbal Medicinal Products |date=24 November 2014 |title=Melaleucae aetheroleum |url=https://www.ema.europa.eu/en/medicines/herbal/melaleucae-aetheroleum}}

Tea tree oil is not recommended for treating nail fungus because it is yet to be proven effective,{{cite journal| vauthors=Halteh P, Scher RK, Lipner SR| title=Over-the-counter and natural remedies for onychomycosis: do they really work? | journal=Cutis | year= 2016 | volume= 98 | issue= 5 | pages= E16–E25 | pmid=28040821 }} 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.{{cite web |publisher=National Health Service |title=Head lice and nits |date=10 January 2018 |url=https://www.nhs.uk/conditions/head-lice-and-nits/}}{{cite journal|doi=10.1016/j.pedhc.2012.05.004|title=Advancements in the Treatment of Head Lice in Pediatrics|year=2012|last1=Eisenhower|first1=Christine|last2=Farrington|first2=Elizabeth Anne|journal=Journal of Pediatric Health Care|volume=26|issue=6|pages=451–61; quiz 462–4|pmid=23099312}} {{As of|2020}}, there is uncertainty regarding the effectiveness of 5-50% tea tree oil as an effective treatment for demodex mite infestations, although products claiming efficacy exist.{{cite journal |vauthors=Savla K, Le JT, Pucker AD |title=Tea tree oil for Demodex blepharitis |journal=Cochrane Database Syst Rev |volume=6 |issue= 6|pages=CD013333 |date=June 2020 |pmid=32589270 |pmc=7388771 |doi=10.1002/14651858.CD013333.pub2 |type=Systematic review}}

Tea tree oil is highly toxic when ingested orally.{{cite web |title=Tea tree oil |url=https://pubchem.ncbi.nlm.nih.gov/compound/22833361 |publisher=PubChem, US National Library of Medicine |access-date=31 October 2021 |date=30 October 2021}}{{cite book |publisher=American Cancer Society |title=American Cancer Society Complete Guide to Complementary and Alternative Cancer Therapies |chapter-url=https://archive.org/details/americancancerso0000unse |chapter-url-access=registration |edition=2nd |year=2009 |isbn=9780944235713 |veditors=Russell J, Rovere A |chapter=Tea Tree Oil |url-access=registration |url=https://archive.org/details/americancancerso0000unse }} It may cause drowsiness, confusion, hallucinations, coma, unsteadiness, weakness, vomiting, diarrhoea, nausea, blood-cell abnormalities, and severe rashes. It should be kept away from pets and children. It should not be used in or around the mouth.{{cite web|url=http://www.poison.org/poisonpost/winter2010/teatreeoil.htm|title=Tea Tree Oil|publisher=National Capital Poison Center|access-date=4 December 2013}}

Application of tea tree oil to the skin can cause an allergic reaction in some, the potential for which increases as the oil ages and its chemical composition changes.{{cite journal| vauthors=de Groot AC, Schmidt E| title=Tea tree oil: contact allergy and chemical composition. | journal=Contact Dermatitis | year= 2016 | volume= 75 | issue= 3 | pages= 129–43 | pmid=27173437 | doi=10.1111/cod.12591 | type=Review | doi-access=free }} Adverse effects include skin irritation, allergic contact dermatitis, systemic contact dermatitis, linear immunoglobulin A disease, erythema multiforme-like reactions, and systemic hypersensitivity reactions.{{cite journal |pages=616–25 |doi=10.1016/j.fct.2005.09.001 |title=A review of the toxicity of Melaleuca alternifolia (tea tree) oil |year=2006 |last1=Hammer |first1=K |last2=Carson |first2=C |last3=Riley |first3=T |last4=Nielsen |first4=J |journal=Food and Chemical Toxicology |volume=44 |issue=5 |pmid=16243420}} Allergic reactions may be due to the various oxidation products that are formed by exposure of the oil to light and air.{{cite journal|last=Aberer|first=W|title=Contact allergy and medicinal herbs|journal=Journal der Deutschen Dermatologischen Gesellschaft|date=January 2008|volume=6|issue=1|pages=15–24|pmid=17919303|doi=10.1111/j.1610-0387.2007.06425.x|s2cid=10292505}} Consequently, oxidised tea tree oil should not be used.{{cite web|title=The Effectiveness and Safety of Australian Tea Tree Oil|url=https://rirdc.infoservices.com.au/downloads/07-143|publisher=Australian Government - Rural Industries and Development Corporation|archive-url=https://web.archive.org/web/20180927165036/https://agrifutures.infoservices.com.au/downloads/07-143|archive-date=27 September 2018|access-date=26 February 2014}}

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.{{cite journal |vauthors=Lee KA, Harnett JE, Cairns R|title=Essential oil exposures in Australia: analysis of cases reported to the NSW Poisons Information Centre |journal=Medical Journal of Australia |year=2019 |volume=212 |issue=3 |pages=132–133 |issn=0025-729X |doi=10.5694/mja2.50403 |pmid=31709543 |doi-access=free }}

Tea tree oil potentially poses a risk for causing abnormal breast enlargement in men{{cite web |title = Breast enlargement in males |url = https://www.nlm.nih.gov/medlineplus/ency/article/003165.htm |website = Medline Plus |publisher = US National Library of Medicine |access-date = 15 November 2015 }}{{cite web |publisher=Endocrine Society |title=Gynecomastia |date=May 2018 |url=https://www.hormone.org/diseases-and-conditions/gynecomastia}} and prepubertal children.{{cite journal |vauthors=Poon SW, Siu KK, Tsang AM |title=Isoniazid-induced gynaecomastia: report of a paediatric case and review of literature |journal=BMC Endocr Disord |volume=20 |issue=1 |pages=160 |date=October 2020 |pmid=33109161 |pmc=7590456 |doi=10.1186/s12902-020-00639-9 |type=Review |doi-access=free }}{{cite journal |vauthors=Restrepo R, Cervantes LF, Swirsky AM, Diaz A |title=Breast development in pediatric patients from birth to puberty: physiology, pathology and imaging correlation |journal=Pediatr Radiol |volume=51 |issue=11 |pages=1959–1969 |date=October 2021 |pmid=34236480 |doi=10.1007/s00247-021-05099-4 |s2cid=235767694 |type=Review}} 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 impacts from the oil.{{cite web |publisher=Endocrine Society |title=Chemicals in lavender and tea tree oil appear to be hormone disruptors |date=19 March 2018 |url=https://www.endocrine.org/news-and-advocacy/news-room/2018/chemicals-in-lavender-and-tea-tree-oil-appear-to-be-hormone-disruptors}}

In dogs and cats, death{{cite web|url=http://www.petpoisonhelpline.com/poison/tea-tree-oil/ |title=Tea Tree Oil and Dogs, Tea Tree Oil and Cats |publisher=Petpoisonhelpline.com |access-date=13 December 2012}}{{cite web |url=http://www.veterinarywatch.com/Abstract-tea-tree-oil.htm |title=Tea Tree Oil Toxicity |publisher=Veterinarywatch |access-date=13 December 2012 |url-status=dead |archive-url=https://web.archive.org/web/20130111031504/http://www.veterinarywatch.com/Abstract-tea-tree-oil.htm |archive-date=11 January 2013 }} 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.{{cite journal|last=Villar|first=D|author2=Knight, MJ |author3=Hansen, SR |author4= Buck, WB |title=Toxicity of melaleuca oil and related essential oils applied topically on dogs and cats|journal=Veterinary and Human Toxicology|date=April 1994|volume=36|issue=2|pages=139–42|pmid=8197716}}

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

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). The oil has been described as colourless to pale yellow having a fresh, camphor-like smell.{{cite book|author=Billee Sharp|title=Lemons and Lavender: The Eco Guide to Better Homekeeping|url=https://books.google.com/books?id=v1MTKm49UqgC&pg=PT43|date=18 September 2013|publisher=Cleis Press|isbn=978-1-936740-11-6|pages=43–}}

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

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.{{Cite web |title=Melaleuca alternifolia |url=https://apps.cals.arizona.edu/arboretum/taxon.aspx?id=824 |access-date=23 June 2023 |website=The University of Arizona}}

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.{{cite journal|doi=10.1128/CMR.19.1.50-62.2006|title=Melaleuca alternifolia (Tea Tree) Oil: A Review of Antimicrobial and Other Medicinal Properties|year=2006|last1=Carson|first1=C. F.|last2=Hammer|first2=K. A.|last3=Riley|first3=T. V.|journal=Clinical Microbiology Reviews|volume=19|pages=50–62|pmid=16418522|issue=1|pmc=1360273}}

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. 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{{Cite web |title=Melaleuca quinquenervia |url=https://plants.ifas.ufl.edu/plant-directory/melaleuca-quinquenervia/ |access-date=23 June 2023 |website=University of Florida}}).

Similar oils can also be produced by water distillation from Melaleuca linariifolia and Melaleuca dissitiflora.{{cite journal|title=Antimicrobial activity of Melaleuca sp. oil against clinical isolates of antibiotics resistant Staphylococcus aureus|author=Sávia Perina Portilho Falci|journal=Acta Cirurgica Brasileira|volume=30|number=7|date=July 2015|doi=10.1590/S0102-865020150060000005|pmid=26108028|pages=401–6|doi-access=free}} 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.

• Cajeput oil — derived from M. cajuputi

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Category:Acne treatments

Category:Antifungals

Category:Antiseptics

Category:Dermatologic drugs

Category:Endocrine disruptors

Category:Essential oils

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Category:Skin care

Category:Traditional medicine

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