Tea tree oil

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Origin of this essential oil, the tea tree, Melaleuca alternifolia Melaleuca alternifolia (Maria Serena).jpg
Origin of this essential oil, the tea tree, Melaleuca alternifolia
Tea tree plantation, Coraki, New South Wales Tea tree plantation.JPG
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.

Contents

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] [3] [4] [5]

Tea tree oil is neither a patented product nor an approved drug in the United States, [2] [5] although it is approved as a complementary medicine for aromatherapy in Australia. [6] It is poisonous if consumed by mouth and is unsafe for children. [7]

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, [5] [8] insufficient evidence exists to support any of these claims due to the limited quality of research. [2] [4] [9] A 2015 Cochrane review of acne complementary therapies found a single low-quality trial showing benefit on skin lesions compared to placebo. [10]

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. [11]

Tea tree oil is not recommended for treating nail fungus because it is yet to be proven effective, [12] 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. [13] [14] There is no good evidence tea tree oil is an effective treatment for demodex mite infestations. [15]

Toxicity

Tea tree oil is highly toxic when ingested orally. [2] [4] [16] [9] 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. [9] It should not be used in or around the mouth. [2] [4] [7]

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. [17] Adverse effects include skin irritation, allergic contact dermatitis, systemic contact dermatitis, linear immunoglobulin A disease, erythema multiforme-like reactions, and systemic hypersensitivity reactions. [8] [18] Allergic reactions may be due to the various oxidation products that are formed by exposure of the oil to light and 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 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. [21]

Hormonal effects

Tea tree oil potentially poses a risk for causing abnormal breast enlargement in men [22] [23] and prepubertal children. [24] [25] 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. [26]

In animals

In dogs and cats, death [27] [28] 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. [29]

As a test of toxicity by oral intake, the median lethal dose (LD50) in rats is 1.9–2.4 ml/kg. [30]

Composition and characteristics

Tea tree oil composition,
as per ISO 4730 (2017) [1]
ComponentConcentration
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] [3] [5] The oil has been described as colorless to pale yellow [1] [2] having a fresh, camphor-like smell. [31]

Tea tree oil products contain various phytochemicals, among which terpinen-4-ol is the major component. [1] [2] [3] Adverse reactions diminish with lower eucalyptol content. [8]

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. [32]

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. [30]

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. [30] 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 [33] ).

Similar oils can also be produced by water distillation from Melaleuca linariifolia and Melaleuca dissitiflora . [34] 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. [5]

See also

Related Research Articles

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Melaleuca is a genus of nearly 300 species of plants in the myrtle family, Myrtaceae, commonly known as paperbarks, honey-myrtles or tea-trees. They range in size from small shrubs that rarely grow to more than 16 m (52 ft) high, to trees up to 35 m (115 ft). Their flowers generally occur in groups, forming a "head" or "spike" resembling a brush used for cleaning bottles, containing up to 80 individual flowers.

<span class="mw-page-title-main">Essential oil</span> Hydrophobic liquid containing volatile aroma compounds from plants

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<span class="mw-page-title-main">Lavender oil</span> Essential oil distilled from lavender flower spikes

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<span class="mw-page-title-main">Herbal medicine</span> Study and use of supposed medicinal properties of plants

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<span class="mw-page-title-main">Cajeput oil</span>

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<i>Melaleuca alternifolia</i> Species of tree in the flowering plant family Myrtaceae

Melaleuca alternifolia, commonly known as tea tree, is a species of tree or tall shrub in the myrtle family, Myrtaceae. Endemic to Australia, it occurs in southeast Queensland and the north coast and adjacent ranges of New South Wales where it grows along streams and on swampy flats, and is often the dominant species where it occurs.

<span class="mw-page-title-main">Mugwort</span> Genus of flowering plants used as herbs

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<span class="mw-page-title-main">Viridiflorol</span> Chemical compound

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