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Tea Tree Oil

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tea tree oil
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Tea tree oil
Tea tree oil composition and chemistry
Tea tree oil benefits
Tea tree oil for acne
Tea tree oil mouthwash
Tea tree oil handwash
Tea tree oil antifungal
Tea tree oil scalp
Tea tree oil for cold sores
Tea tree oil against MRSA colonization
Tea tree oil side effects
Oral toxicity
Skin toxicity
Cutaneous and mucosal reactions
Allergic reactions

Tea tree oil

Tea tree oil also known as Melaleuca oil, Australian tea tree oil, tea tree essential oil or tea tree, is the essential oil extracted using steam distillation of the leaves and terminal branches of Melaleuca alternifolia (tea tree), a tree native to Australia 1. Herbal medicines containing tea tree oil preparations are usually available in liquid or semi-solid forms to be applied to the skin and in liquid forms to be applied to the lining of the mouth. Tea tree oil preparations may also be found in combination with other herbal substances in some herbal medicines. Tea tree oil is used as a topical antibacterial, antifungal, antiviral, anti-inflammatory and analgesic properties due to the presence of terpineol (terpinen-4-ol) and α-terpineol 2. Tea tree (Melaleuca alternifolia) is an Australian species from the northern coast with a high content of terpineol (terpinen-4-ol) (more than 30% of gross weight) and low content of cineole (lower than 15%) 3. Terpinen-4-ol is the main antimicrobial component but other components, such as α-terpineol, also have antimicrobial activities similar to those of terpinen-4-ol 4. Some of the chemical and physical properties of tea tree oil components are shown in Tables 1 and 2 below. The concentrations of tea tree oil found in commercially available products range from 2 to 5% 5. Although the oil comprises a variable and complex mixture of over 100 components, its composition has been described as being approximately a 50/50 blend of oxygenated and nonoxygenated monoterpenes 6. The essential oil from the Melaleuca leaves, because of its antinflammatory and antibacterial properties, is widely used in the traditional medicine among the native Australian population to treat infections of the urinary tract, fingernails, skin, and acne 7. Due to tea tree oil components, such as terpinen-4-ol, α-terpineol, linalool, α-pinene, β-pinene, β-myrcene and 1,8-cineole, tea tree essential oil has demonstrated an high degree of antibacterial effect against a wide range of bacteria (Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus spp, vancomycin resistant enterococci [VRE], Acinetobacter baumanni, Escherichia coli, Klebisella pulmonae), fungi (Candida spp, Malassezia spp) and protozoa (Trichomonas vaginalis) 8. Tea tree oil has also been used in a spray form to control castor bean ticks (Ixodes ricinus) and poultry red mites (Dermanyssus gallinae) in poultry houses 8. The composition of tea tree oil may change considerably during storage, with ρ-cymene levels increasing and α- and γ-terpinene levels declining 9. Light, heat, exposure to air, and moisture all affect oil stability, and tea tree oil should be stored in dark, cool, dry conditions, preferably in a vessel that contains little air.

Terpenes are a class of organic compounds produced by a variety of plants 10 and animals, expecially some insects 11. The use of synthetic and natural terpenes in medicine is widely documented. Epidemiological studies suggest that dietary monoterpenes may be helpful in the prevention and therapy of cancers 12, fungal 13, bacterial 14, and parasitic diseases 15. Despite of the facts, literature about the use of this substances as therapeutics in veterinary medicine is still lacking 16. There are some papers about the toxicity of Melaleuca alternifolia and its extract 17, but only few reports about the toxicity of other terpenes and their metabolites.

In Australia, “tea trees” are also known as “paperbark trees” and collectively these terms may refer to species in the Melaleuca or Leptospermum genera, of which there are several hundred. For instance, common names for Melaleuca cajuputi include “swamp tea tree” and “paperbark tea tree,” while those for Melaleuca quinquenervia include “broad-leaved tea tree” and “broad-leaved paperbark” 18. Many Leptospermum species are cultivated as ornamental plants and are often mistakenly identified as the source of tea tree oil. In addition, the essential oils kanuka and manuka, derived from the New Zealand plants Kunzea ericoides and Leptospermum scoparium, respectively, are referred to as New Zealand tea tree oils 19 although they are very different in composition from Australian tea tree oil 20.

As explained below, the international standard for tea tree oil does not specify which Melaleuca species must be used to produce oil. Rather it sets out the requirements for an oil chemotype. Oils that meet the requirements of the standard have been distilled from Melaleuca species other than Melaleuca alternifolia, including Melaleuca dissitiflora, Melaleuca linariifolia, and Melaleuca uncinata 21. However, in practice, commercial tea tree oil is produced from Melaleuca alternifolia (Maiden and Betche) Cheel. The Melaleuca genus belongs to the Myrtaceae family and contains approximately 230 species, almost all of which are native to Australia 22. When left to grow naturally, Melaleuca alternifolia grows to a tree reaching heights of approximately 5 to 8 meters 23. Trees older than 3 years typically flower in October and November 24 and flowers are produced in loose, white to creamy colored terminal spikes, which can give trees a “fluffy” appearance 25.

Tea tree oil should not be swallowed. Taking it orally can cause serious symptoms such as confusion, ataxia (loss of muscle coordination), breathing problems, and coma.

Most people can use topical products containing tea tree oil without problems, but some people may develop contact dermatitis (an allergic skin rash) or skin irritation on the parts of the body where the product was used.

Little is known about whether it’s safe to use tea tree oil during pregnancy or while breastfeeding.

Tea tree oil composition and chemistry

The term “Tea Tree” includes species of the genus Leptospermum and Melaleuca (more than 230 species) of the family Myrtaceae 7. The best known and economically most important species is the Australian Tea Tree. Tea tree oil is composed of terpene hydrocarbons, mainly monoterpenes, sesquiterpenes, and their associated alcohols. Terpenes are volatile, aromatic hydrocarbons and may be considered polymers of isoprene, which has the formula C5H8. Early reports on the composition of tea tree oil described 12 26, 21 27 and 48 28 components. The seminal paper by Brophy and colleagues 9 examined over 800 tea tree oil samples by gas chromatography and gas chromatography-mass spectrometry and reported approximately 100 components and their ranges of concentrations (Table ​1).

Given the scope for batch-to-batch variation, it is fortunate that the composition of oil sold as tea tree oil is regulated by an international standard for “Oil of Melaleuca—terpinen-4-ol type,” which sets maxima and/or minima for 14 components of the oil (Table 1) 29. Consequently, to optimize antimicrobial activity, a lower limit of 30% and no upper limit were set for terpinen-4-ol content.  Notably, the international standard for “Oil of Melaleuca terpinen-4-ol” does not stipulate the species of Melaleuca from which the tea tree oil must be sourced. Instead, it sets out physical and chemical criteria for the desired chemotype. Six varieties or chemotypes, of Melaleuca alternifolia have been described, each producing oil with a distinct chemical composition. These include a terpinen-4-ol chemotype, a terpinolene chemotype, and four 1,8-cineole chemotypes 30. The terpinen-4-ol chemotype typically contains levels of terpinen-4-ol of between 30 to 40% 30 and is the chemotype used in commercial tea tree oil production. Despite the inherent variability of commercial tea tree oil, no obvious differences in its bioactivity either in vitro (test tube study) or in vivo (animal study) have been noted so far. The suggestion that oil from a particular Melaleuca alternifolia clone possesses enhanced microbicidal activity has been made 31, but the evidence is not compelling.

For many years cineole was erroneously considered to be a skin and mucous membrane irritant, fuelling efforts to minimize its level in tea tree oil 3. This reputation was based on historical anecdotal evidence and uncorroborated statements 3 and repetition of this suggestion appears to have consolidated the myth. Recent data do not indicate that 1,8-cineole is an irritant 3. Although minimization of 1,8-cineole content on the basis of reducing adverse reactions is not warranted, it remains an important consideration since 1,8-cineole levels are usually inversely proportional to the levels of terpinen-4-ol 9, one of the main antimicrobial components of tea tree oil 32.

Table 1. Composition of tea tree oil (Melaleuca alternifolia oil)

ComponentComposition (%)

 

ISO 4730 range a
Typical composition b
Terpinen-4-ol≥30 c40.1
γ-Terpinene01/10/2823
α-Terpinene01/05/1310.4
1,8-Cineole≤15d5.1
Terpinolene01/05/053.1
ρ-Cymene0.5-122.9
α-Pinene01/06/212.6
α-Terpineol01/05/082.4
AromadendreneTrace-71.5
δ-CadineneTrace-81.3
Limonene0.5-41
SabineneTrace-3.50.2
GlobulolTrace-30.2
ViridiflorolTrace-1.50.1

Footnotes:

a IOS 4730, International Organization for Standardization standard no. 4730 29
b From reference 9
c No upper limit is set, although 48% has been proposed.
d No lower limit is set.

[Source 3 ]

Table 2. Properties of tea tree oil components

ComponentType of compoundChemical formulaSolubility (ppm) 33Log KOW b
Terpinen-4-olMonocyclic terpene alcoholC10H18O14913.26
γ-TerpineneMonocyclic terpeneC10H1614.36
α-TerpineneMonocyclic terpeneC10H168.24.25
1,8-CineoleMonocyclic terpene alcoholC10H18O9072.84
α-TerpinoleneMonocyclic terpeneC10H164.34.24
ρ-CymeneMonocyclic terpeneC10H146.2
(+)-α-PineneDicyclic terpeneC10H160.574.44
α-TerpineolMonocyclic terpene alcoholC10H18O18273.28
AromadendreneSesquiterpeneC15H24
δ-CadineneSesquiterpeneC15H24
(+)-LimoneneMonocyclic terpeneC10H1614.38
SabineneDicyclic monoterpeneC10H16
GlobulolSesquiterpene alcoholC15H26O

Footnote: b Kow, octanol-water partition coefficient, from reference 34

[Source 3 ]

Tea tree oil benefits

Currently, tea tree oil is used in cosmetics and healthcare products and has recently re-emerged as an effective antiseptic 35. A limited number of published controlled clinical trials support this latter use 36. Data from some of the more recent clinical investigations are summarized in Table ​3.

Tea tree oil has been used successfully in oral candidosis in AIDS (acquired immunodeficiency syndrome) patients 37 and other oral fungal infections in patients suffering from advanced cancer 38.

There are a number of limitations to the clinical studies described below. Several had low numbers of participants, meaning that statistical analyses could not be performed or differences did not reach significance 3. Many studies had ambiguous and/or equivocal outcomes. Of those studies with larger numbers of patients, few reported 95% confidence intervals or relative risk values. While most studies compared the efficacy of tea tree oil to a placebo, many did not compare tea tree oil to a conventional therapy or treatment regimen, again limiting the conclusions that could be drawn about efficacy 3. Therefore, although some of these data indicate that tea tree oil has potential as a therapeutic agent, confirmatory studies are required. In addition, factors such as the final tea tree oil concentration, product formulation, and length and frequency of treatment undoubtedly influence clinical efficacy, and these factors must be considered in future studies 3. The cost-effectiveness of any potential tea tree oil treatments must also be considered. For example, tea tree oil therapy may offer no cost advantage over the azoles in the treatment of tinea but is probably more economical than treatment with the allylamines 3.

The Committee on Herbal Medicinal Products concluded that, on the basis of its long-standing use, tea tree oil preparations can be used for the treatment of small superficial wounds, insect bites and small boils (furuncles and mild acne), for the relief of itching and irritation in mild athlete’s foot, and for the treatment of minor inflammation of the lining of the mouth 39. Tea tree oil medicines should only be used in adults and adolescents over the age of 12 years. They should not be taken for longer than 1 month when treating small boils or itching and irritation in mild athlete’s foot. If symptoms continue or worsen during the use of the medicine a doctor or a qualified healthcare practitioner should be consulted.

Overall, a monograph on Melaleuca alternifolia and/or other species of Melaleuca, aetheroleum radix is recommended with the following preparations and therapeutic indications 7:

  1. Traditional herbal medicinal product for treatment of small superficial wounds and insect bites: liquid preparation containing 0.5% to 10% of tea tree essential oil to be applied on the affected area 1-3 times daily.
  2. Traditional herbal medicinal product for treatment of small boils (furuncles and mild acne): oily liquid or semi-solid preparations containing 10% of tea tree essential oil, to be applied on the affected area 1-3 times daily or 0,7-1 ml of essential oil stirred in 100 ml of lukewarm water to be applied as an impregnated dressing to the affected areas of the skin.
  3. Traditional herbal medicinal product for the relief of itching and irritation in cases of mild athlete’s foot: oily liquid or semi-solid preparations containing 10% of tea tree essential oil, to be applied on the affected area 1-3 times daily.
  4. Traditional herbal medicinal product for symptomatic treatment of minor inflammation of oral mucosa: 0.17 – 0.33 ml of tea tree oil to be mixed in 100 ml of water for rinse or gargle several times dailyfor symptomatic treatment of minor inflammation of oral mucosa.
  5. A limited amount of research indicates that tea tree oil might be helpful for acne and athlete’s foot. One small study suggests that tea tree oil might help with nail fungus. But overall, the research is insufficient to allow clear conclusions to be reached about the use of tea tree oil for these conditions.
  6. Some early research shows that tea tree oil might be promising for treating mite infections at the base of the eyelids (also called ocular demodicosis). The current evidence is insufficient, however, for a clear conclusion.

Table 3. Summary of clinical studies using tea tree oil

Study populationStudy typeTreatment groups (no. of evaluable patients)Administration of treatmentOutcomesAdverse eventsReference
124 patients with mild to moderate acneRandomized controlled trial, investigator blinded b5% tea tree oil gel (58), 5% benzoyl peroxide (61)3 monthsBoth significantly reduced inflamed lesions but benzoyl peroxide better than tea tree oil; benzoyl peroxide better at reducing oiliness; less scaling, pruritis (itch), dryness with tea tree oil; treatments equivalent for noninflamed lesions, erythema27 (44%) in tea tree oil group, 50 (79%) in benzoyl peroxide group (e.g., dryness, stinging, burning, redness); significantly fewer events in tea tree oil group40
18 patients with recurrent herpes labialis (cold sores)Randomized controlled trial, investigator blinded b6% tea tree oil gel (9), placebo gel (9)5 times dailyMedian time to reepithelization of 9 days for tea tree oil vs 12.5 days for placebo (not significant)1 in tea tree oil group (event not stated)41
126 patients with mild to moderate dandruffRandomized controlled trial, investigator blinded b5% tea tree oil shampoo (63), placebo shampoo (62)Daily for 4 weekWhole scalp lesion score significantly improved in tea tree oil group (41.2%) compared to placebo group (11.2%)3 (5%) in tea tree oil group, 8 (13%) in placebo group (e.g., mild burning, stinging, itching)42
30 hospital inpatients colonized or infected with MRSARandomized, controlled pilot study4% tea tree oil nasal ointment + 5% tea tree oil body wash (15), 2% mupirocin nasal ointment + Triclosan body wash (15)Frequency not stated, minimum of 3 daysFor tea tree oil, 33% cleared, 20% chronic, 47% incomplete; for routine treatment, 3% cleared, 53% chronic, 33% incomplete (no significant differences)With tea tree oil nasal ointment (no. not stated), mild swelling of nasal mucosa to acute burning43
236 hospital patients colonized with MRSARandomized controlled trial10% tea tree oil cream + 5% tea tree oil body wash (110), 2% mupirocin nasal ointment + 4% Triclosan body wash + 1% silver sulfadiazine cream (114)Once daily for 5 daysFor tea tree oil, 41% cleared; for routine treatment, 49%cleared; treatment regimens did not differ significantly; mupirocin significantly better than tea tree oil at clearing nasal carriageNone44
117 patients with culture-positive onychomycosisRandomized controlled trial, double blind100% tea tree oil (64), 1% clotrimazole (53)Twice daily for 6 monthsFull or partial resolution for 60% of tea tree oil and 61% of clotrimazole patients after 6 months of therapy (not significant)5 (7.8%) in tea tree oil group, 3 (5.7%) in clotrimazole group (erythema, irritation, edema)45
60 outpatients with a clinical diagnosis of onychomycosisRandomized controlled trial, double blind2% butenafine hydrochloride with 5% tea tree oil cream (40), 5% tea tree oil cream (20)3 times daily for 8 weekCure in 80% of butenafine/tea tree oil group and 0% of tea tree oil group4 (10%) in butenafine/tea tree oil group (mild inflammation)46
13 patients with AIDS and fluconazole-refractory oral candidiasisCase seriesMelaleuca oral solution (15 ml) (12)4 times daily for 2-4 weekClinical response rate of 67% after 4 weeks (cure in 2 patients, improvement in 6 patients, no response in 4 patients, 1 deterioration)None47
27 patients with AIDS and fluconazole-refractory oral candidiasisOpen-label trialMelaleuca oral solution (15 ml) (12), alcohol-free melaleuca oral solution (5 ml)c (13)4 times daily for 2-4 weekMycological and clinical response in 58% (alcohol-based solution) and 54% (alcohol-free solution) of patients after 4 wk8 (66.7%) in alcohol-based solution group, 2 (15.4%) in alcohol-free solution group (mild to moderate burning)48
121 patients with clinically diagnosed tinea pedisrandomized controlled trial, double blind10% tea tree oil in sorbolene (37), 1% tolnaftate (33), placebo (sorbolene) (34)Twice daily for 4 weekMycological cure and clinical improvement in 46% (tolnaftate), 22% (tea tree oil), and 9% (placebo) of patients; tolnaftate significantly better than placebo (P = 0.003) but not tea tree oil (P = 0.59); tea tree oil not different from placebo (P = 0.3)None49
137 patients with culture-positive tinea pedisrandomized controlled trial, double blind25% tea tree oil (36), 50% tea tree oil (38), placebo (46)Twice daily for 4 weekEffective cure in 48% (25% tea tree oil), 50% (50% tea tree oil), and 13% (placebo) of patients; tea tree oil significantly better than placebo (P < 0.0005)1 (2.8%) in 25% tea tree oil group, 3 (7.9%) in 50% tea tree oil group (moderate to severe dermatitis)50

Footnotes:

b The distinctive odor of tea tree oil was stated as preventing patient blinding.
c The alcohol-free solution was more concentrated, and thus a smaller volume was used.

[Source 3 ]

Tea tree oil for acne

One of the first rigorous clinical studies assessed the efficacy of 5% tea tree oil in the treatment of acne by comparing it to 5% benzoyl peroxide 51. The study found that both 5% tea tree oil and 5% benzoyl peroxide treatments reduced the numbers of inflamed lesions, although benzoyl peroxide performed significantly better than tea tree oil 51. The benzoyl peroxide group showed significantly less oiliness than the tea tree oil group, whereas the tea tree oil group showed significantly less scaling, pruritis (itch) and dryness. Significantly fewer overall side effects were reported by the tea tree oil group (27 of 61 patients) than by the benzoyl peroxide group (50 of 63 patients) 51.

Tea tree oil mouthwash

The efficacy of tea tree oil in dental applications has been assessed. An evaluation of the effect of a 0.2% tea tree oil mouthwash and two other active agents on the oral flora of 40 volunteers suggested that tea tree oil used once daily for 7 days could reduce the number of mutans streptococci and the total number of oral bacteria, compared to placebo treatment 3. The data also indicated that these reductions were maintained for 2 weeks after the use of mouthwash ceased 52. In another study 53, comparison of mouthwashes containing either approximately 0.34% tea tree oil, 0.1% chlorhexidine, or placebo on plaque formation and vitality, using eight volunteers, showed that after tea tree oil treatment, both plaque index and vitality did not differ from those of subjects receiving placebo mouthwash on any day, whereas the results for the chlorhexidine mouthwash group differed significantly from those for the placebo group on all days 53. Lastly, a study comparing a 2.5% tea tree oil gel, a 0.2% chlorhexidine gel, and a placebo gel found that although the tea tree oil group had significantly reduced gingival index and papillary bleeding index scores, their plaque scores were actually increased 54. These studies indicate that although tea tree oil may cause decreases in the levels of oral bacteria, this does not necessarily equate to reduced plaque levels. However, tea tree oil may have a role in the treatment of gingivitis, and there is also some evidence preliminary suggesting that tea tree oil reduces the levels of several compounds associated with halitosis 55.

Tea tree oil has also been evaluated as a mouthwash in the treatment of oropharyngeal candidiasis. In a case series, 13 human immunodeficiency virus (HIV) positive patients who had already failed treatment with a 14-day course of oral fluconazole were treated with an alcohol-based tea tree oil solution for up to 28 days 56. After treatment, of the 12 evaluable patients, 2 were cured, 6 were improved, 4 were unchanged, and 1 had deteriorated. Overall, eight patients had a clinical response and seven had a mycological response. In subsequent work the same tea tree oil solution was compared with an alcohol-free tea tree oil solution 37. Of patients receiving the alcohol-based solution, two were cured, six improved, four were unchanged, and one had deteriorated. Of patients receiving the alcohol-free solution, five were cured, two improved, two were unchanged, and one had deteriorated. Three patients were lost to follow-up and were considered nonresponders.

Tea tree oil handwash

For many years there has been considerable interest in the possibility of using tea tree oil in handwash formulations for use in hospital or health care settings. It is well known that handwashing is an effective infection control measure and that lack of compliance is related to increased rates of nosocomial infections. The benefits of using tea tree oil in a handwash formulation include its antiseptic effects and increased handwashing compliance. A recent handwash study 57 using volunteers showed that either a product containing 5% tea tree oil and 10% alcohol or a solution of 5% tea tree oil in water performed significantly better than soft soap, whereas a handwash product containing 5% tea tree oil did not.

Tea tree oil antifungal

With regard to fungal infections, tea tree oil has been clinically evaluated for the treatment of onychomycosis (also known as fungal nail infection or tinea unguium) 46, tinea pedis (foot infection due to a dermatophyte fungus) 50, dandruff 58, and oral candidiasis 48. Although much has been made of the potential for tea tree oil to be used in the treatment of vaginal candidiasis, no clinical data have been published. However, results from an animal (rat) model of vaginal candidiasis support the use of tea tree oil for the treatment of this infection 59.

In the first of the onychomycosis trials 45, 60% of patients treated with tea tree oil and 61% of patients treated with 1% clotrimazole had full or partial resolution. There were no statistically significant differences between the two treatment groups for any parameter. The second onychomycosis trial 46 compared two creams, one containing 5% tea tree oil alone and the other containing 5% tea tree oil and 2% butenafine, both applied three times daily for 8 weeks. The overall cure rate was 0% for patients treated with 5% tea tree oil alone, compared to 80% for patients treated with both butenafine and tea tree oil 46. Unfortunately, butenafine alone was not evaluated. The observation that tea tree oil may be useful adjunct therapy for onychomycosis has been made by Klimmek et al. 60. However, onychomycosis is considered to be largely unresponsive to topical treatment of any kind, and a high rate of cure should therefore not be expected.

The effectiveness of tea tree oil in treating tinea pedis has been evaluated in two trials. In the first trial, patients were treated with 10% tea tree oil in sorbolene, 1% tolnaftate, or placebo (sorbolene) 49. At completion of treatment, patients treated with tea tree oil had mycological cure and clinical improvement rates of 30% and 65%, respectively 49. This compares to mycological cure rates of 21% in patients receiving placebo and 85% in patients receiving tolnaftate. Similarly, clinical improvement was seen in 41% of patients receiving placebo and 68% of patients receiving tolnaftate. In a second tinea trial 50, the efficacy of solutions of 25% and 50% tea tree oil in ethanol and polyethylene glycol was compared to treatment with placebo (vehicle). Marked clinical responses were seen in 72% and 68% of patients in the 25% and 50% tea tree oil treatment groups, respectively, compared to 39% of patients in the placebo group. Similarly, there were mycological cures of 55% and 64% in the 25% and 50% tea tree oil treatment groups, respectively, compared to 31% in the placebo group 50. Dermatitis occurred in one patient in the 25% tea tree oil group and in three patients in the 50% tea tree oil group. This led to the recommendation that 25% tea tree oil be considered an alternative treatment for tinea, since it was associated with fewer adverse reactions than but was just as effective as 50% tea tree oil 50. These studies highlight the importance of considering the formulation of the tea tree oil product when conducting in vivo work, since it is likely that the sorbolene vehicle used in the first tinea trial may have significantly compromised the antifungal activity of the oil.

Tea tree oil scalp

The evaluation of a 5% tea tree oil shampoo for mild to moderate dandruff demonstrated statistically significant improvements in the investigator-assessed whole scalp lesion score, total area of involvement score, and total severity score, as well as in the patient-assessed itchiness and greasiness scores, compared to placebo. Overall, the 5% tea tree oil was well tolerated and appeared to be effective in the treatment of mild to moderate dandruff.

Tea tree oil for cold sores

Support for tea tree oil possessing antiviral activity comes from a pilot study investigating the treatment of recurrent cold sores (herpes labialis) with a 6% tea tree oil gel or a placebo gel 61. Comparison of the patient groups (each containing nine evaluable patients) at the end of the study showed that reepithelialization after treatment occurred after 9 days for the tea tree oil group and after 12.5 days for the placebo group 61. Other measures, such as duration of virus positivity by culture or PCR, viral titers, and time to crust formation, were not significantly different, possibly due to small patient numbers. Interestingly, when tea tree oil was evaluated for its protective efficacy in an in vivo mouse model of genital  herpes simplex virus type 2 (HSV type 2) infection, it did not perform well 62. In contrast, the oil component 1,8-cineole performed well, protecting 7 of 16 animals from disease.

Tea tree oil against MRSA colonization

Two studies have assessed the efficacy of tea tree oil for the eradication of methicillin-resistant Staphylococcus aureus (MRSA) carriage. The effectiveness of a 4% tea tree oil nasal ointment and a 5% tea tree oil body wash was compared to that of conventional treatment with mupirocin nasal ointment and Triclosan body wash in a small pilot study 63. Of the 15 patients receiving conventional treatment, 2 were cleared and 8 remained colonized at the end of therapy; in the tea tree oil group of 15, 5 were cleared and 3 remained colonized 63. The remainder of patients did not complete therapy. Differences in clearance rates were not statistically significant, most likely due to the low patient numbers. Stronger evidence for the efficacy of tea tree oil in decolonizing MRSA carriage comes from a recent trial in which 236 patients were randomized to receive standard or tea tree oil treatment regimens 64. The standard regimen consisted of 2% mupirocin nasal ointment applied three times a day, 4% chlorhexidine gluconate soap applied at least once a day, and 1% silver sulfadiazine cream applied to skin lesions, wounds, and leg ulcers once a day, all for 5 days. The tea tree oil regimen consisted of 10% tea tree oil nasal cream applied three times a day, 5% tea tree oil body wash applied at least once daily and 10% tea tree oil cream applied to skin lesions, wounds, and leg ulcers once a day, all for 5 days 64. The 10% tea tree oil cream was allowed to be used as an alternative to the body wash. Follow-up swabs were taken at 2 and 14 days post-treatment, with the exception of 12 patients who were lost to follow-up. Evaluation of the remaining 224 patients showed no significant differences between treatment regimens, with 49% of patients receiving standard therapy cleared versus 41% of patients in the tea tree oil group 64. In a case report, a combination of plant extracts of which tea tree oil was a major component was inserted percutaneously into bone to treat an intractable MRSA infection of the lower tibia, which subsequently resolved 65. This same essential oil solution has now been shown to aid in the healing of malodorous malignant ulcers 66.

Tea tree oil side effects

Despite the progress in characterizing the antimicrobial and anti-inflammatory properties of tea tree oil, less work has been done on the safety and toxicity of the oil. The rationale for continued use of the oil rests largely on the apparently safe use of the oil for almost 80 years. Anecdotal evidence over this time suggests that topical use is safe and that adverse events are minor, self-limiting, and infrequent. More concrete evidence such as published scientific work is scarce, and much information remains out of the public domain in the form of reports from company-sponsored work.

Side effects reported with tea tree oil medicines include skin reactions such as pain, mild itching, burning sensation, irritation, stinging, redness and swelling, and other allergic reactions. Their frequency is unknown.

Burn-like skin reactions have been reported rarely (in between 1 and 10 patients in 10,000).

Clinical studies and traditional use show that short-term use (not more than 1 month) of diluted tea tree oil on skin or mucosa is safe, but it is not suitable to be used in the eye or ear. Reported adverse events were minor and mostly limited to local irritation. A case of blistering dermatitis has been reported with a wart paint containing tea tree oil used for a period of 4 months. There is some evidence that 100% tea tree oil can cause allergic reactions in some patients. The rate of allergic reactions reported in the literature in various patch testing studies ranges between 0.6% and 2.4% (mean 1.6%). The incidence and strength of the reactions is generally higher with oxidised tea tree oil samples. Proper storage and handling of tea tree oil and its formulated products should avoid the development of these by-products and reduce the risk of skin irritation and sensitisation in sensitive individuals. Oral use results in poisoning. Accidental ingestion of 10-25 ml, demonstrates that at these relatively high doses, tea tree oil causes central nervous system (CNS) depression and muscle weakness. However, these symptoms had generally resolved within 36 hours.tea tree oil was not genotoxic in in-vivo mouse micronucleus test (up to 1750 mg/kg). Ames test data are incomplete. Tests on reproductive toxicity and on carcinogenicity have not been performed.

There is insufficient data to support the safety of tea tree oil during pregnancy and lactation or in children under 12 years and therefore the use in this population groups is not recommended as a precautionary measure.

The oral and dermal toxicities of tea tree oil are summarized briefly below.

Oral toxicity

Tea tree oil can be toxic if ingested, as evidenced by studies with animals and from cases of human poisoning. The 50% lethal dose (LD 50) for tea tree oil in a rat model is 1.9 to 2.6 ml/kg body weight 67, and rats dosed with ≤1.5 g/kg body weight tea tree oil appeared lethargic and ataxic 68. LD50 is the amount of a material, given all at once, which causes the death of 50% (one half) of a group of test animals. The LD50 is one way to measure the short-term poisoning potential (acute toxicity) of a material. Several cases of human tea tree oil poisoning have been reported, mostly involving the ingestion of modest volumes (10-25 ml ) of oil. In two cases, ingestion of tea tree oil resulted in what appeared to be systemic contact dermatitis 69. It has been reported the case of a patient comatose for the first 12 hours and then semi-conscious for the following 36 hours after ingestion of approximately half a cup of tea tree oil. Other cases reported that two children who ingested less than 10 ml tea tree oil became ataxic and drowsy or disorientated. Both were treated supportively and recovered fully without further complications 69. Ingestion of significant quantities of tea tree oil has been described in a 17-month-old male who ingested less than 10 ml of the pure oil (100%) and developed ataxia and drowsiness 70. Accidental poisonings following tea tree oil ingestion, demonstrate that at relatively high doses, tea tree oil causes central nervous system (CNS) depression and muscle weakness 71. However, these symptoms had generally resolved within 36 hours.

Incidences of oral poisoning in children 72, 73, 71 and adults 74, 75 have been reported. In all cases, patients responded to supportive care and recovered without apparent complications.

No human deaths due to tea tree oil have been reported in the literature.

Skin toxicity

Tea tree oil can cause both irritant and allergic reactions. A mean irritancy score of 0.25 has been found for neat tea tree oil, based on patch testing results for 311 volunteers 76. Another study, in which 217 patients from a dermatology clinic were patch tested with 10% tea tree oil, found no irritant reactions 77. Since irritant reactions may frequently be avoided through the use of lower concentrations of the irritant, this bolsters the case for discouraging the use of neat oil and promoting the use of well-formulated products. Allergic reactions have been reported 78 and although a range of components have been suggested as responsible, the most definitive work indicates that they are caused mainly by oxidation products that occur in aged or improperly stored oil 79. There is little scientific support for the notion that 1,8-cineole is the major irritant in tea tree oil. No evidence of irritation was seen when patch testing was performed on rabbits with intact and abraded skin 80, guinea pigs 79 and humans 81, including those who had previous positive reactions to tea tree oil 82. Rarely, topically applied tea tree oil has been reported to cause systemic effects in domestic animals. Dermal application of approximately 120 ml of undiluted tea tree oil to three cats with shaved but intact skin resulted in symptoms of hypothermia, uncoordination, dehydration, and trembling and in the death of one of the cats 83.

Cutaneous and mucosal reactions

Adverse skin reactions like smarting pain, itch, and allergic reactions have been reported. The frequency is not known. Burn-like skin reaction has been reported in Denmark. The frequency is rare (<1/1.000). There have been case reports of dermal sensitivity, contact dermatitis related to tea tree oil. Varma et al. reported a case of vaginal application of tea tree oil and lavender oil in a patient with concurrent severe eczema 84. Bhushan and Beck 85 reported a case of blistering dermatitis where a wart paint containing tea tree oil had been used for a period of 4 months. The man had a positive patch test to 1% tea tree oil, while 50 controls were negative on testing with 1% and 5% aqueous tea tree solutions. The case patient was treated with topical corticosteroids and recovered with no known sequelae 84. It has been reported the case of a 18 year female patient in whom linear Immunoglobulin A (IgA) disease appears to have been precipitated by a contact reaction to tea tree oil. Linear IgA disease is a rare acquired subepidermal blistering disorder, characterized by basement membrane zone IgA deposition 86.

Allergic reactions

Very rarely allergic dermatitis may occur during the use of tea tree essential oil without any dilution. Allergic skin reactions reported in Denmark are not common (≥1/1.000 and < 1/100). At the Skin and Cancer Foundation (Sydney, NSW, Australia), three of 28 normal volunteers tested strongly positive to patch testing with tea tree oil. Following further patch testing with tea tree oil constituents, all three patients reacted strongly to two preparations containing sesquiterpenoid fractions of the oil 87.

References
  1. Markham, J.L. (1999) Biological activity of tea tree oil. In Tea Tree, the Genus Melaleuca ed. Southwell, I. and Lowe, R. pp. 169 190. Amsterdam: Harwood Academic publishers.
  2. Carson, C. F., Riley, T. V. & Cookson, B. D. (1998). Efficacy and safety of tea tree oil as a topical antimicrobial agent. Journal of Hospital Infection 40, 175–8.
  3. 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. https://doi.org/10.1128/CMR.19.1.50-62.2006
  4. Carson, C. F. & Riley, T. V. (1995). Antimicrobial activity of the major components of the essential oil of Melaleuca alternifolia. Journal of Applied Bacteriology 78, 264–9.
  5. Carson, C. F., Cookson, B. D., Farrelly, H. D. & Riley, T. V. (1995). Susceptibility of methicillin-resistant Staphylococcus aureus to the essential oil of Melaleuca alternifolia. Journal of Antimicrobial Chemotherapy 35, 421–4.
  6. Brophy, J.J., Davies, N.W., Southwell, I.A., Stiff, I.A., Williams, L.R. (1989) Gas chromatographic quality control for oil of Melaleuca Terpinen‐4‐ol Type (Australian Tea Tree). Journal of Agricultural and Food Chemistry 37, 1330 1335.
  7. EMA/HMPC. Assessment report on Melaleuca alternifolia (Maiden and Betch) Cheel, M.linarifolia Smith , M.dissitiflora F.Mueller and /or other species of Melaleuca, Aetheroleum. Eur Med Agency. 2013. https://www.ema.europa.eu/en/documents/herbal-report/draft-assessment-report-melaleuca-alternifolia-maiden-betch-cheel-m-linariifolia-smith-m/other-species-melaleuca-aetheroleum_en.pdf
  8. Puvača N, Čabarkapa I, Petrović A, Bursić V, Prodanović R, Soleša D, Lević J. Tea tree (Melaleuca alternifolia) and its essential oil: antimicrobial, antioxidant and acaricidal effects in poultry production. Worlds Poult Sci J. 2019;75(2):235–246. doi: 10.1017/S0043933919000229
  9. Brophy, J. J., N. W. Davies, I. A. Southwell, I. A. Stiff, and L. R. Williams. 1989. Gas chromatographic quality control for oil of Melaleuca terpinen-4-ol type (Australian tea tree). J. Agric. Food Chem. 37:1330-1335.
  10. Langenheim JH. Higher plant terpenoids: a phytocentric overview of their ecological roles. J Chem Ecol. 1994;20:1223–1280. doi: 10.1007/BF02059809
  11. Breitmaier E. Terpenes: Flavors, Fragrances, Pharmaca, Pheromones. Weinheim: Wiley; 2006. ISBN 978-3527317868
  12. Paduch R, Kandefer-Szerszeń M, Trytek M, Fiedurek J. Terpenes: substances useful in human healthcare. Arch Immunol Ther Exp. 2007;55(5):315. doi: 10.1007/s00005-007-0039-1
  13. Parveen M, Kamrul H, Junko T, Yoshinori M, Emiko K, Osamu K, Hitoshi I. Response of Saccharomyces cerevisiae to a monoterpene: evaluation of antifungal potential by DNA microarray analysis. J Antimicrob Chemother. 2004;54:46–55. doi: 10.1093/jac/dkh245
  14. Trombetta D, Castelli F, Sarpietro MG, Venuti V, Cristani M, Daniele C, Saija A, Mazzanti G, Bisignano G. Mechanisms of antibacterial action of three monoterpenes. Antimicrob Agents Chemother. 2005;49:2474–2478. doi: 10.1128/AAC.49.6.2474-2478.2005
  15. Robledo S, Osorio E, Munoz D, Jaramillo LM, Restrepo A, Arango G, Velez I. In vitro and in vivo cytotoxicities and antileishmanial activities of thymol and hemisynthetic derivatives. Antimicrob Agents Chemother. 2005;49:1652–1655. doi: 10.1128/AAC.49.4.1652-1655.2005
  16. AbouLaila M, Sivakumar T, Yokoyama N, Igarashi I. Inhibitory effect of terpene nerolidol on the growth of Babesia parasites. Parasitol Int. 2010;59(2):278–282. doi: 10.1016/j.parint.2010.02.006
  17. Hammer KA, Carson CF, Riley TV, Nielsen JB. A review of the toxicity of Melaleuca alternifolia (tea tree) oil. Food Chem Toxicol. 2006;44:616–625. doi: 10.1016/j.fct.2005.09.001
  18. Lassak, E. V., and T. McCarthy. 1983. Australian medicinal plants, p.93-99, 115. Methuen Australia, North Ryde, Australia.
  19. Christoph F, Kaulfers PM, Stahl-Biskup E. A comparative study of the in vitro antimicrobial activity of tea tree oils s.l. with special reference to the activity of beta-triketones. Planta Med. 2000 Aug;66(6):556-60. doi: 10.1055/s-2000-8604
  20. Perry, N. B., N. J. Brennan, J. W. Van Klink, W. Harris, M. H. Douglas, J. A. McGimpsey, B. M. Smallfield, and A. R. E. 1997. Essential oils from New Zealand manuka and kanuka: chemotaxonomy of Leptospermum. Phytochemistry 44:1485-1494.
  21. Murtagh, J. G. 1999. Biomass and oil production of tea tree, p. 109-133. In I. Southwell and R. Lowe (ed.), Tea tree: the genus Melaleuca, vol. 9. Harwood Academic Publishers, Amsterdam, The Netherlands.
  22. Craven, L. A. 1999. Behind the names: the botany of tea tree, cajuput and niaouli, p. 11-28. In I. Southwell and R. Lowe (ed.), Tea tree: the genus Melaleuca, vol. 9. Harwood Academic Publishers, Amsterdam, The Netherlands.
  23. Colton, R. T., and G. J. Murtagh. 1999. Cultivation of tea tree, p. 63-78. In I. Southwell and R. Lowe (ed.), Tea tree: the genus Melaleuca, vol. 9. Harwood Academic Publishers, Amsterdam, The Netherlands.
  24. Baker, G. 1999. Tea tree breeding, p. 135-154. In I. Southwell and R. Lowe (ed.), Tea tree: the genus Melaleuca, vol. 9. Harwood Academic Publishers, Amsterdam, The Netherlands.
  25. Weiss, E. A. 1997. Essential oil crops. CAB International, New York, N.Y.
  26. Guenther, E. 1968. Australian tea tree oils. Report of a field survey. Perfum. Essent. Oil Rec. 59:642-644.
  27. Altman, P. M. 1988. Australian tea tree oil. Aust. J. Pharm. 69:276-278.
  28. Swords, G., and G. L. K. Hunter. 1978. Composition of Australian tea tree oil (Melaleuca alternifolia). J. Agric. Food Chem. 26:734-737.
  29. International Organisation for Standardisation. 2004. ISO 4730:2004. Oil of Melaleuca, terpinen-4-ol type (tea tree oil). International Organisation for Standardisation, Geneva, Switzerland.
  30. Homer LE, Leach DN, Lea D, Slade Lee L, Henry RJ, Baverstock PR. Natural variation in the essential oil content of Melaleuca alternifolia Cheel (Myrtaceae). Biochem Syst Ecol. 2000 Apr 1;28(4):367-382. doi: 10.1016/s0305-1978(99)00071-x
  31. J. May, C. H. Chan, A. King, L. Williams, G. L. French, Time–kill studies of tea tree oils on clinical isolates, Journal of Antimicrobial Chemotherapy, Volume 45, Issue 5, May 2000, Pages 639–643, https://doi.org/10.1093/jac/45.5.639
  32. Hammer KA, Carson CF, Riley TV. Antifungal activity of the components of Melaleuca alternifolia (tea tree) oil. J Appl Microbiol. 2003;95(4):853-60. doi: 10.1046/j.1365-2672.2003.02059.x
  33. Griffin, S. G., S. G. Wyllie, J. L. Markham, and D. N. Leach. 1999. The role of structure and molecular properties of terpenoids in determining their antimicrobial activity. Flav. Fragr. J. 14:322-332.
  34. Griffin, S. G., S. G. Wyllie, and J. L. Markham. 1999. Determination of octanol-water partition coefficients for terpenoids using reversed-phase high-perfrormance liquid chromatography. J. Chromatogr. A 864:221-228.
  35. Williams, L. R., Stockley, J. K., Home, V. N. & Yan, W. (1997). Therapeutic use for tea tree oil. Australian Journal of Pharmacy 78, 285–7.
  36. Buck, D. S., Nidorf, D. M. & Addino, J. G. (1994). Comparison of two topical preparations for the treatment of onychomycosis: Melaleuca alternifolia (tea tree) oil and clotrimazole. Journal of Family Practice 36, 601–5.
  37. Vazquez JA, Zawawi AA. Efficacy of alcohol-based and alcohol-free melaleuca oral solution for the treatment of fluconazole-refractory oropharyngeal candidiasis in patients with AIDS. HIV Clin Trials. 2002 Sep-Oct;3(5):379-85. doi: 10.1310/99dy-8q52-306a-v0aj
  38. Bagg J, Jackson MS, Petrina Sweeney M, Ramage G, Davies AN. Susceptibility to Melaleuca alternifolia (tea tree) oil of yeasts isolated from the mouths of patients with advanced cancer. Oral Oncol. 2006 May;42(5):487-92. doi: 10.1016/j.oraloncology.2005.10.002
  39. Melaleucae aetheroleum. https://www.ema.europa.eu/en/medicines/herbal/melaleucae-aetheroleum
  40. Bassett, I. B., D. L. Pannowitz, and R. S. Barnetson. 1990. A comparative study of tea-tree oil versus benzoylperoxide in the treatment of acne. Med. J. Aust. 153:455-458.
  41. Carson, C. F., L. Ashton, L. Dry, D. W. Smith, and T. V. Riley. 2001. Melaleuca alternifolia (tea tree) oil gel (6%) for the treatment of recurrent herpes labialis. J. Antimicrob. Chemother. 48:450-451.
  42. Satchell, A. C., A. Saurajen, C. Bell, and R. S. Barnetson. 2002. Treatment of dandruff with 5% tea tree oil shampoo. J. Am. Acad. Dermatol. 47:852-855.
  43. Caelli, M., J. Porteous, C. F. Carson, R. Heller, and T. V. Riley. 2000. Tea tree oil as an alternative topical decolonization agent for methicillin-resistant Staphylococcus aureus. J. Hosp. Infect. 46:236-237.
  44. Dryden, M. S., S. Dailly, and M. Crouch. 2004. A randomized, controlled trial of tea tree topical preparations versus a standard topical regimen for the clearance of MRSA colonization. J. Hosp. Infect. 56:283-286.
  45. Buck, D. S., D. M. Nidorf, and J. G. Addino. 1994. Comparison of two topical preparations for the treatment of onychomycosis: Melaleuca alternifolia (tea tree) oil and clotrimazole. J. Fam. Pract. 38:601-605.
  46. Syed, T. A., Z. A. Qureshi, S. M. Ali, S. Ahmad, and S. A. Ahmad. 1999. Treatment of toenail onychomycosis with 2% butenafine and 5% Melaleuca alternifolia (tea tree) oil in cream. Trop. Med. Int. Health 4:284-287.
  47. Jandourek, A., J. K. Vaishampayan, and J. A. Vazquez. 1998. Efficacy of melaleuca oral solution for the treatment of fluconazole refractory oral candidiasis in AIDS patients. AIDS 12:1033-1037.
  48. Vazquez, J. A., and A. A. Zawawi. 2002. Efficacy of alcohol-based and alcohol-free melaleuca oral solution for the treatment of fluconazole-refractory oropharyngeal candidiasis in patients with AIDS. HIV Clin. Trials 3:379-385.
  49. Tong, M. M., P. M. Altman, and R. S. Barnetson. 1992. Tea tree oil in the treatment of tinea pedis. Aust. J. Dermatol. 33:145-149.
  50. Satchell, A. C., A. Saurajen, C. Bell, and R. S. Barnetson. 2002. Treatment of interdigital tinea pedis with 25% and 50% tea tree oil solution: a randomized, placebo controlled, blinded study. Australas. J. Dematol. 43:175-178.
  51. Bassett, I.B., Barnetson, R.S.C. and Pannowitz, D.L. (1990), A comparative study of tea‐tree oil versus benzoylperoxide in the treatment of acne. Medical Journal of Australia, 153: 455-458. https://doi.org/10.5694/j.1326-5377.1990.tb126150.x
  52. Groppo FC, Ramacciato JC, Simões RP, Flório FM, Sartoratto A. Antimicrobial activity of garlic, tea tree oil, and chlorhexidine against oral microorganisms. Int Dent J. 2002 Dec;52(6):433-7. doi: 10.1111/j.1875-595x.2002.tb00638.x
  53. Arweiler NB, Donos N, Netuschil L, Reich E, Sculean A. Clinical and antibacterial effect of tea tree oil–a pilot study. Clin Oral Investig. 2000 Jun;4(2):70-3. doi: 10.1007/s007840050118
  54. Soukoulis, S. and Hirsch, R. (2004), The effects of a tea tree oil‐containing gel on plaque and chronic gingivitis. Australian Dental Journal, 49: 78-83. https://doi.org/10.1111/j.1834-7819.2004.tb00054.x
  55. Takarada, K. 2005. The effects of essential oils on periodontopathic bacteria and oral halitosis. Oral Dis. 11:115.
  56. Jandourek, Alena1; Vaishampayan, Julie K.1; Vazquez, Jose A.1,2 Efficacy of melaleuca oral solution for the treatment of fluconazole refractory oral candidiasis in AIDS patients, AIDS: September 1998 – Volume 12 – Issue 9 – p 1033-1037. https://journals.lww.com/aidsonline/Fulltext/1998/09000/Efficacy_of_melaleuca_oral_solution_for_the.11.aspx
  57. Messager S, Hammer KA, Carson CF, Riley TV. Effectiveness of hand-cleansing formulations containing tea tree oil assessed ex vivo on human skin and in vivo with volunteers using European standard EN 1499. J Hosp Infect. 2005 Mar;59(3):220-8. doi: 10.1016/j.jhin.2004.06.032
  58. Satchell AC, Saurajen A, Bell C, Barnetson RS. Treatment of dandruff with 5% tea tree oil shampoo. J Am Acad Dermatol. 2002 Dec;47(6):852-5. doi: 10.1067/mjd.2002.122734
  59. Mondello, F., F. De Bernardis, A. Girolamo, G. Salvatore, and A. Cassone. 2003. In vitro and in vivo activity of tea tree oil against azole-susceptible and -resistant human pathogenic yeasts. J. Antimicrob. Chemother. 51:1223-1229.
  60. Klimmek, J. K., R. Nowicki, K. Szendzielorz, M. Kunicka, R. Rosentrit, G. Honisz, and W. Krol. 2002. Application of a tea tree oil and its preparations in combined treatment of dermatomycoses. Mikol. Lekarska 9:93-96.
  61. C. F. Carson, L. Ashton, L. Dry, D. W. Smith, T. V. Riley, Melaleuca alternifolia (tea tree) oil gel (6%) for the treatment of recurrent herpes labialis, Journal of Antimicrobial Chemotherapy, Volume 48, Issue 3, September 2001, Pages 450–451, https://doi.org/10.1093/jac/48.3.450
  62. Bourne KZ, Bourne N, Reising SF, Stanberry LR. Plant products as topical microbicide candidates: assessment of in vitro and in vivo activity against herpes simplex virus type 2. Antiviral Res. 1999 Jul;42(3):219-26. doi: 10.1016/s0166-3542(99)00020-0
  63. Caelli M, Porteous J, Carson CF, Heller R, Riley TV. Tea tree oil as an alternative topical decolonization agent for methicillin-resistant Staphylococcus aureus. J Hosp Infect. 2000 Nov;46(3):236-7. doi: 10.1053/jhin.2000.0830
  64. Dryden MS, Dailly S, Crouch M. A randomized, controlled trial of tea tree topical preparations versus a standard topical regimen for the clearance of MRSA colonization. J Hosp Infect. 2004 Apr;56(4):283-6. doi: 10.1016/j.jhin.2004.01.008
  65. Sherry E, Boeck H, Warnke PH. Topical application of a new formulation of eucalyptus oil phytochemical clears methicillin-resistant Staphylococcus aureus infection. Am J Infect Control. 2001 Oct;29(5):346. doi: 10.1067/mic.2001.117403
  66. Warnke PH, Sherry E, Russo PA, Sprengel M, Açil Y, Bredee JP, Schubert S, Wiltfang J, Springer IN. Antibacterial essential oils reduce tumor smell and inflammation in cancer patients. J Clin Oncol. 2005 Mar 1;23(7):1588-9. doi: 10.1200/JCO.2005.05.380
  67. Russell, M. 1999. Toxicology of tea tree oil, p. 191-201. In I. Southwell and R. Lowe (ed.), Tea tree: the genus Melaleuca, vol. 9. Harwood Academic Publishers, Amsterdam, The Netherlands.
  68. D. Kim, D. R. Cerven, S. Craig, and G. L. De George, Abstr. Amer. Chem. Soc. 223:114, 2002
  69. Carson CF, Riley TV, Cookson BD. Efficacy and safety of tea tree oil as a topical antimicrobial agent. J Hosp Infect. 1998 Nov;40(3):175-8. doi: 10.1016/s0195-6701(98)90135-9
  70. Halcon, L. and Milkus, K. (2004)Staphylococcus aureusandwounds: a review of tea tree oil as a promising antimicro-bial.Am J Infect Control32, 402–408.
  71. Morris MC, Donoghue A, Markowitz JA, Osterhoudt KC. Ingestion of tea tree oil (Melaleuca oil) by a 4-year-old boy. Pediatr Emerg Care. 2003 Jun;19(3):169-71. doi: 10.1097/01.pec.0000081241.98249.7b
  72. Del Beccaro MA. Melaleuca oil poisoning in a 17-month-old. Vet Hum Toxicol. 1995 Dec;37(6):557-8.
  73. Jacobs MR, Hornfeldt CS. Melaleuca oil poisoning. J Toxicol Clin Toxicol. 1994;32(4):461-4. doi: 10.3109/15563659409011050
  74. Elliott C. Tea tree oil poisoning. Med J Aust. 1993 Dec 6-20;159(11-12):830-1. doi: 10.5694/j.1326-5377.1993.tb141370.x
  75. Seawright, A. 1993. Tea tree oil poisoning. Med. J. Aust. 159:831.
  76. Aspres, N., and S. Freeman. 2003. Predictive testing for irritancy and allergenicity of tea tree oil in normal human subjects. Exogenous Dermatol. 2:258-261.
  77. Veien NK, Rosner K, Skovgaard GL. Is tea tree oil an important contact allergen? Contact Dermatitis. 2004 Jun;50(6):378-9. doi: 10.1111/j.0105-1873.2004.0350f.x
  78. van der Valk PG, de Groot AC, Bruynzeel DP, Coenraads PJ, Weijland JW. Allergisch contacteczeem voor ‘tea tree’-olie [Allergic contact eczema due to ‘tea tree’ oil]. Ned Tijdschr Geneeskd. 1994 Apr 16;138(16):823-5. Dutch.
  79. Hausen BM, Reichling J, Harkenthal M. Degradation products of monoterpenes are the sensitizing agents in tea tree oil. Am J Contact Dermat. 1999 Jun;10(2):68-77. doi: 10.1016/s1046-199x(99)90002-7
  80. Opdyke, D. L. J. 1975. Fragrance raw materials monographs (eucalyptol). Food Cosmet. Toxicol. 13:105-106.
  81. Southwell, I. A., S. Freeman, and D. Rubel. 1997. Skin irritancy of tea tree oil. J. Essent. Oil Res. 9:47-52.
  82. Knight, T. E., and B. M. Hausen. 1994. Melaleuca oil (tea tree oil) dermatitis. J. Am. Acad. Dermatol. 30:423-427.
  83. Bischoff, K., and F. Guale. 1998. Australian tea tree (Melaleuca alternifolia) oil poisoning in three purebred cats. J. Vet. Diagn. Investig. 10:208-210.
  84. Halcón L, Milkus K. Staphylococcus aureus and wounds: a review of tea tree oil as a promising antimicrobial. Am J Infect Control. 2004 Nov;32(7):402-8. doi: 10.1016/S0196655304003657
  85. Bhushan M, Beck MH. Allergic contact dermatitis from tea tree oil in a wart paint. Contact Dermatitis. 1997 Feb;36(2):117-8. doi: 10.1111/j.1600-0536.1997.tb00435.x
  86. Perrett, C.M., Evans, A.V. and Russell‐Jones, R. (2003), Tea tree oil dermatitis associated with linear IgA disease. Clinical and Experimental Dermatology, 28: 167-170. https://doi.org/10.1046/j.1365-2230.2003.01229.x
  87. Rubel, D.M., Freeman, S. and Southwell, I.A. (1998), Tea tree oil allergy: What is the offending agent? Report of three cases of tea tree oil allergy and review of the literature. Australasian Journal of Dermatology, 39: 244-247. https://doi.org/10.1111/j.1440-0960.1998.tb01482.x
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