Tea Tree Oil

Scientific Name(s): Melaleuca alternifolia Cheel.
Common Name(s): Melaleuca oil, Tea tree oil

Medically reviewed by Drugs.com. Last updated on Feb 13, 2023.

Clinical Overview

Use

Despite an abundance of commercial preparations promoted for antimicrobial use, sound clinical trials are limited. Studies have been conducted in conditions including nail infections, athlete's foot, fungal skin infections, acne, methicillin-resistant Staphylococcus aureus (MRSA) colonization, and hemorrhoids. Case reports exist for use in other conditions.

Dosing

Decolonization of MRSA: Tea tree oil as a nasal cream (4% to 10%) applied 3 times a day for 5 days and 5% body wash for 5 days. Prevention of MRSA colonization: Body wash containing 5% tea tree oil daily. Acne vulgaris: 5% tea tree oil gel applied for 20 minutes twice daily, then washed off. Onchomycosis (fungal nail infections): 100% tea tree oil applied for 6 months. Tinea pedis (athlete's foot): 25% to 50% tea tree oil for 4 weeks.

Contraindications

Oral ingestion is contraindicated.

Pregnancy/Lactation

Information regarding safety and efficacy in pregnancy and lactation is lacking.

Interactions

None well documented.

Adverse Reactions

Case reports exist of dermatitis associated with topical tea tree oil.

Toxicology

Tea tree oil is toxic when ingested orally. Some case studies of accidental and intentional poisoning exist; however, no deaths have been reported to the American Association of Poison Control Centers through 2012. Mutagenicity of tea tree oil appears to be low; however, chemical constituents have been shown to be cytotoxic and embryotoxic.

Scientific Family

• Myrtaceae

Botany

There are many plants known as tea trees, but the species M. alternifolia is the source of tea tree essential oil. Native to Australia coastal areas, the tea tree is an evergreen shrub that grows from 5 to 8 m in height. Its narrow, 4 cm, needle-like leaves release a distinctive aroma when crushed. The fruits grow in clusters, and its white flowers bloom in the summer. Ornamental Leptospermum species are distinct and are not the source of tea tree oil. Related species include Melaleuca quinquenervia (Cav.) S.T. Blake (Melaleuca viridiflora sol.), a New Caledonian evergreen tree that yields niaouli oil, Melaleuca leucaden L., and Melaleuca cajuputi Powell (synonym, Melaleuca minor Sm.), which is the source of oil of cajuput that contains similar chemical constituents.1, 2

History

The indigenous people of Australia have used tea tree oil from crushed leaves as a traditional remedy for coughs and colds, as well as to treat wounds and skin conditions. Tea tree oil was first used in surgery and dentistry in the mid-1920s. Its healing properties were also used during World War II for skin injuries in munitions factory workers. Tea tree oil's popularity has increased in recent years as interest in natural therapies evolves, and it can be found in soaps, shampoos, and lotions.2, 3

Chemistry

The essential oil is normally obtained by steam distillation of the leaves and terminal branchlets, resulting in a transparent, colorless to pale yellow oil with a characteristic odor. The main constituent in tea tree's essential oil and present in concentrations of 30% or more is terpinen-4-ol, with more than 100 other constituents identified. The International Standards Organization requires 15 of these chemicals to be present, and concentrations of terpinen-4-ol must be at least 30% and 1,8-cineole (controversially considered a skin irritant) must be less than 15%. However, essential oils from other related species (Melaleuca dissitiflora and Melaleuca linariifolia) can also meet these same standards and have been used as adulterants. Other constituents include terpene endoperoxide (ascaridole), terpinene, terpinolene, pinene, cymene, and limonene. The composition of the essential oil may change with storage conditions, because heat, light, air, and moisture can affect the oil.2, 3, 4

Uses and Pharmacology

Acne/Antibacterial

In vitro studies have confirmed bactericidal and bacteriostatic (at lower concentrations) action of tea tree oil. A broad spectrum of bacterial pathogens are affected, including common skin Staphylococcus species, Enterococcus faecalis, Pseudomonas aeruginosa, as well as Propionibacterium acnes, and most are susceptible to concentrations of 1% or less of tea tree essential oil; however, the minimum inhibitory concentration (MIC) of some pathogens is as high as 8%. The activity has been attributed mainly to terpineol content, but some studies suggest that cineole has a role.(2, 5, 6, 7) The leaf extract of the related species M. quinquenervia is considered weakly active against Helicobacter pylori with a MIC of 100 mcg/mL.(40, 43)

Animal data

A limited number of dermatological studies have been conducted in animals, particularly for chronic itching and fleas in dogs, but toxicity associated with ingesting the oil via licking limits therapeutic applications.(2, 3, 8, 9)

Clinical data

Despite the large number of in vitro studies published, few quality clinical trials have been conducted. Clinical studies have been conducted in acne, methicillin-resistant S. aureus, and gingivitis. Case reports exist for use in bacterial vaginitis.(10)

One small trial established 5% tea tree oil to be more effective than placebo over 45 days in treating mild to moderate acne vulgaris.(11) A second trial demonstrated equivalence with benzoyl peroxide 5% over 3 months of treatment; however, it may have been insufficiently powered to detect a difference.(12) A Cochrane review of complementary therapies for acne identified 1 randomized trial (n=60) of low quality that showed a statistically significant benefit of tea tree oil gel for reducing the numbers of skin lesions in acne vulgaris compared to placebo (P<0.00001). Tea tree gel was applied for 20 minutes/day for a duration of 45 days. Adverse effects were minimal and similar between groups.(42) Similar results were reported in a 12-week uncontrolled, open-label phase II pilot study with use of tea tree facial wash and gel in 18 adults. Total lesion counts and mean percentage decreases were significant at 4, 8, and 12 weeks. Acne severity was rated as about the same by 46% and slightly improved by 43% of participants. Treatment was well tolerated.(43)

In studies evaluating tea tree oil in the decolonization of MRSA nasal application of ointment (4% to 10%) and body wash (5%), no difference was shown versus mupirocin 2% and chlorhexidine or triclosan.(13, 14) In subgroup analysis of data from the larger trial, mupirocin nasal ointment performed better than 10% tea tree oil in nasal decolonization, while tea tree oil performed better than chlorhexidine in decolonizing the skin and skin lesions.(14) The results of a multicenter, open-label, randomized clinical trial on the effect of 5% tea tree oil wash in preventing methicillin-resistant S. aureus colonization in patients in the intensive care unit (ICU) was undertaken by a group of investigators in Northern Ireland.(15) In this study (n = 391 evaluable), 5% tea tree oil body wash or control was used at least daily for bed baths until ICU discharge, or detection of MRSA colonization. There was no significant difference between treatment groups for incidence of MRSA colonization, and no patient in either group developed MRSA bacteremia.(35)

In 2 small trials, 0.34% tea tree oil mouthwash and 2.5% tea tree oil gel reduced gingival inflammation but did not decrease plaque scores versus chlorhexidine or placebo.(16, 17)

The American Academy of Dermatology/American Academy of Dermatology Association guidelines of care for the management of acne vulgaris (2016) states that topical tea tree oil is effective for the treatment of acne (limited; moderate).(41)

Antifungal

A wide range of yeasts, dermatophytes, and other filamentous fungi were susceptible to varying concentrations of tea tree oil. Reported MICs range from 0.12% to 2%, but some species (eg, Aspergillus niger ) require higher concentrations of up to 8%. It has been suggested that different phases of fungal growth are affected differently by tea tree oil.(2, 3, 10, 18, 19)

Clinical data

Despite an abundance of commercial preparations promoted for antifungal use, clinical trials of sound methodology are limited. Trials have been conducted in conditions including nail infections (onchomycosis), athlete's foot (tinea pedis), ringworm (tinea versicolor), dandruff, oral candidiasis, and case reports of other fungal conditions.

Equivalence was found for 100% tea tree oil and clotrimazole 1% in treating onchomycosis over 6 months in one study.(20) However, a study evaluating butenafine with tea tree oil versus tea tree oil alone in treating fungal toenail infections found no effect for tea tree oil alone (the placebo arm of the study) applied over 8 weeks.(21)

Tea tree oil (25% and 50%) was better than placebo in treating tinea pedis in one clinical trial.(22) A second trial found 10% tea tree oil to be no better than placebo in attaining a negative culture, but equivalent to tolnaftate 1% as assessed by reduction of symptoms.(23) The popularity of tea tree oil in treating tinea pedis is attributed to the reduction of scaling, itching, and burning symptoms.(8)

A 5% tea tree oil shampoo used for 4 weeks was shown to be effective in treating dandruff, (24) and in an open-label study with no control arm, tea tree oil resolved oral candidial lesions in some, but not all, patients who were positive for HIV.(25)

Anti-inflammatory action

Anti-inflammatory action has been described for tea tree oil and may account for observed clinical response of reduced itching. In histamine studies and nickel-induced contact hypersensitivity tests, tea tree oil reduced flare and erythema at higher concentrations (20% to 100%).(2, 8, 28, 29, 37)

Antiparasitic

Clinical data

A Cochrane systematic review and meta-analysis assessed the use of topical tea tree oil for symptom management and/or treatment of Demodex mite blepharitis. Overall, data from 6 randomized controlled trials of low to very low quality (N=562) were unclear regarding effectiveness of 5% to 50% tea tree oil for 4 to 12 weeks in reducing mites; however, the authors noted that low concentration may help prevent Demodex-induced ocular irritation.(36)

Antiviral

In vitro data

Early studies examined the antiviral action of tea tree oil on tobacco mosaic virus, while in vitro studies in human viruses have been limited mainly to the herpes simplex viruses.(2, 3) At 2.5 mcg/mL, tea tree oil suppressed herpes simplex virus type 1 in an in vitro study examining various oils.(26)

Clinical data

A small pilot study found some benefit in using a 6% tea tree oil gel in the treatment of recurrent herpes labialis over placebo; however, statistical significance was not achieved.(27)

Dry eye

Clinical data

Continuing dry eye in older adults (79% female) who had undergone phacoemulsification cataract surgery showed significant improvement in some parameters after administration of eye shampoo containing tea tree oil compared to controls. Demodex ocular mites, which were positively correlated with increased age and ocular surface disease index scores, were found in 69.4% of patients and decreased significantly after treatment with eye shampoo with tea tree oil compared to eye shampoo without tea tree oil (P<0.001). Additionally, tear break-up time, osmolarity, and ocular surface disease index scores improved significantly with treatment compared to controls (P<0.05). In contrast, improvements in Schirmer test results as well as corrected and uncorrected distance visual acuity were not significantly different between groups. The study was a triple-blinded, randomized, controlled trial that enrolled 62 patients (mean age, 66 years).(45)

Other uses

In limited experiments, tea tree oil induced apoptosis and cell cycle arrest in tumor cell lines.(9, 30)

Tea tree oil was not effective in improving symptoms of dementia.(31)

Of 31 complementary and alternative medicine (CAM) remedies, tea tree oil was recommended by 36% of German dentists and maxillofacial surgeons for dental issues according to a prospective, cross-sectional survey (N=250). As one might expect, perceived effectiveness was rated higher among CAM proponents than opponents.(44) Tea tree oil was not found to be effective in improving symptoms of dental irrigation in root canal treatment.(32)

Dosing

Decolonization of methicillin-resistant Staphylococcus aureus

Tea tree oil as a nasal cream (4% to 10%) applied 3 times a day for 5 days, and 5% body wash for 5 days.13, 14, 15

Methicillin-resistant Staphylococcus aureus colonization prevention

Tea tree oil 5% body wash was used at least daily in 1 study that found no significant reduction in the rate of MRSA colonization.35

Acne vulgaris

5% tea tree oil gel applied for 20 minutes twice daily, then washed off.11, 12

Onchomycosis (fungal nail infections)

100% tea tree oil applied for 6 months.20

Tinea pedis (athlete's foot)

25% to 50% tea tree oil for 4 weeks.22, 23

Pregnancy / Lactation

Information regarding safety and efficacy in pregnancy and lactation is lacking. Alpha-terpinene, present in tea tree oil, was embryotoxic in rats.9

Interactions

None well documented.

Adverse Reactions

Case reports describe the irritant effect of topical tea tree oil in contact dermatitis.3, 9, 33 However, the irritant effect of tea tree oil, often attributed to the cineole constituent, has been disputed because 1,8-cineole concentrations of up to 28% have not produced reactions.2, 9 A study of tea tree oil in contact dermatitis reduced the concentration of tea tree oil from 50% to 20% because of skin irritation with the higher concentration.37 A relatively low concentration (ie, 1%) of ascaridole, a terpene endoperoxide that can develop in tea tree oil, has been shown to be a potential sensitizer based on data from 2 case studies.39

Toxicology

Tea tree oil is toxic when ingested orally. The median lethal dose in rats has been estimated to be 1.9 to 2.6 mL/kg.2, 9

Some case studies of accidental and intentional poisoning exist; however, no deaths were reported to the American Association of Poison Control Centers through 2012.2, 9, 38

Internal doses of 10 to 70 mL have resulted in ataxia and decreasing levels of consciousness. Activated charcoal and sorbitol have been used as an antidote in cases of poisoning in children. No ongoing neurological sequelae have been reported.9

Reports of cytotoxicity experienced with tea tree oil vary, and mutagenicity is likewise unclear but appears to be low based on experimental data.9, 26 Ototoxicity has been evaluated in guinea pigs, and strengths of 2% or less are considered safe for use.9

Index Terms

• Melaleuca cajuputi Powell
• Melaleuca leucaden L.
• Melaleuca minor Sm.
• Melaleuca quinquenervia (Cav.) S.T. Blake
• Melaleuca viridiflora sol.

References

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This information relates to an herbal, vitamin, mineral or other dietary supplement. This product has not been reviewed by the FDA to determine whether it is safe or effective and is not subject to the quality standards and safety information collection standards that are applicable to most prescription drugs. This information should not be used to decide whether or not to take this product. This information does not endorse this product as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this product. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this product. This information is not specific medical advice and does not replace information you receive from your health care provider. You should talk with your health care provider for complete information about the risks and benefits of using this product.

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