This article is about essential oil isolated from the leaves of the tea tree,Melaleuca alternifolia. For the sweet seasoning oil pressed fromCamellia seeds,C. sinensis orC. oleifera, seetea seed oil.
Tea tree oil, also known asmelaleuca oil, is anessential oil with a fresh,camphoraceousodour and a colour that ranges from pale yellow to nearly colourless and clear.[1][2] It is derived from theleaves of the tea tree,Melaleuca alternifolia, native to southeastQueensland and the northeast coast ofNew South Wales, Australia. The oil comprises many constituent chemicals, and its composition changes if it is exposed to air andoxidises. Commercial use of tea tree oil began in the 1920s, pioneered by the entrepreneurArthur Penfold.
Although tea tree oil is claimed to be useful for treatingdandruff,acne,lice,herpes,insect bites,scabies, and skinfungal orbacterial infections,[6][9] and while evidence exists to support some of these claims,[10][11] there are a limited number of research studies.[12][2][5][13] A 2015Cochrane review of acne complementary therapies found a single low-quality trial showing benefit on skin lesions compared toplacebo.[14] Tea tree oil was also used duringWorld War II to treat skin lesions of munitions factory workers.[2]
According to theCommittee on Herbal Medicinal Products (CHMP) of theEuropean 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.[15]
Tea tree oil is not recommended for treatingnail fungus because it is yet to be proven effective,[16] 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 orallergic reactions.[17][18] Tea tree oil is one of many natural products promoted as a treatment fordemodex mite infestations, but there is uncertainty about the effectiveness of 5-50% solution, and any overall effectiveness is offset by unwanted adverse effects and toxicity.[19][20] Tea tree oil exhibits anti-microbial,anti-fungal andantibacterial properties.[21]
Tea tree oil is highly toxic when ingested orally.[2][5][22][13] 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.[13] 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 in some,[2] the potential for which increases as the oil ages and its chemical composition changes.[23] Adverse effects include skin irritation, allergic contact dermatitis, systemiccontact dermatitis,linear immunoglobulin A disease,erythema multiforme-like reactions, and systemichypersensitivity reactions.[9][24] Allergic reactions may be due to the various oxidation products that are formed by exposure of the oil to light and air.[24][25] Consequently, oxidised tea tree oil should not be used.[26]
In Australia, tea tree oil is one of the manyessential 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.[27]
In dogs and cats, death[33][34] 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.[35]
Tea tree oil is defined by the International StandardISO 4730 ("Oil ofMelaleuca,terpinen-4-ol type"), containing terpinen-4-ol, γ-terpinene, and α-terpinene as about 70% to 90% of whole oil, whilep-cymene, terpinolene, α-terpineol, andα-pinene collectively account for some 15% of the oil (table).[1][4][6] The oil has been described as colourless to pale yellow[1][2] having a fresh,camphor-like smell.[37]
The name "tea tree" is used for several plants, mostly fromAustralia andNew Zealand, from the familyMyrtaceae related to themyrtle. The use of the name probably originated fromCaptain James Cook's description of one of these shrubs that he used to make aninfusion to drink in place oftea.[38]
The commercial tea tree oil industry originated in the 1920s when Australian chemistArthur Penfold investigated the business potential of a number of native extracted oils; he reported that tea tree oil had promise, as it exhibitedantiseptic properties.[36]
Tea tree oil was firstextracted fromMelaleuca 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 fromM. alternifolia. Many of these plantations are located in New South Wales.[36] Since the 1970s and 80s, the industry has expanded to include several other species for their extracted oil:Melaleuca armillaris andMelaleuca styphelioides in Tunisia and Egypt;Melaleuca leucadendra in Egypt, Malaysia, and Vietnam;Melaleuca acuminata in Tunisia;Melaleuca ericifolia in Egypt; andMelaleuca quinquenervia in the United States (considered an invasive species in Florida[39]).
Similar oils can also be produced by water distillation fromMelaleuca linariifolia andMelaleuca dissitiflora.[40] Whereas the availability andnonproprietary 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]
^Halteh P, Scher RK, Lipner SR (2016). "Over-the-counter and natural remedies for onychomycosis: do they really work?".Cutis.98 (5):E16–E25.PMID28040821.
^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.PMID23099312.
^Restrepo R, Cervantes LF, Swirsky AM, Diaz A (October 2021). "Breast development in pediatric patients from birth to puberty: physiology, pathology and imaging correlation".Pediatr Radiol (Review).51 (11):1959–1969.doi:10.1007/s00247-021-05099-4.PMID34236480.S2CID235767694.
^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.PMID8197716.
.jpg)
