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Clinical and antibacterial effect of tea tree oil--a pilot study.

The aim of this clinical pilot study was to compare the effect of tea tree oil with the effect of water and chlorhexidine on supragingival plaque formation and vitality. Eight subjects were asked to refrain from any kind of mechanical oral hygiene for 4 days after professional tooth cleaning (day 0), and to rinse with water instead for 1 week, with chlorhexidine in a second and tea tree oil in a third test week. The plaque index (PI), which was evaluated daily (days 1-4), served as a clinical control parameter. On the last day of the study (day 4), the plaque covering the front teeth was stained, photographed, and therefrom the plaque area (PA; %) was estimated using a digital measuring system. Each day of the study (days 1-4), the sampled plaque was examined using a vital fluorescence technique. Tea tree oil reduced neither the clinical parameters (PI and PA) nor the vitality of the plaque flora significantly. Within the limitations of the study design, it was determined that a solution with tea tree oil--utilized as ordinary mouthwash--has no positive effect on the quantity or quality of supragingival plaque.

Adult↗

Tea tree oil: in vitro efficacy in otitis externa.

OBJECTIVE: The purpose of this study was to determine the susceptibility of organisms causing otitis externa (OE) to the essential oil of Melaleuca alternifolia, or tea tree oil (TTO). METHODS: Fifty-seven swabs were taken from the ears of 52 patients with OE for culture and sensitivity. A broth microdilution method was used to determine the minimum inhibitory concentration (MIC) of TTO for each organism. RESULTS: In 51 percent of the swabs taken, pathogenic organisms were cultured. Of these cultures 71 percent, both bacteria and yeast, were susceptible to TTO 2 percent or less. The only organism showing resistance to TTO was Pseudomonas aeruginosa; however 25 percent of these bacteria were sensitive. CONCLUSION: Tea tree oil may have a role to play in the treatment of OE. However, more work needs to be done to enhance the anti-pseudomonal effect and to assess ototoxicity.

Adolescent↗

[Allergic contact eczema due to 'tea tree' oil].

In four patients, three women aged 45, 29 and 52 years and a man aged 45 years, allergic contact dermatitis due to 'tea tree' oil was diagnosed. The case of the man was published before. 'Tea tree' oils are essential oils distilled from the leaves of myrtaceous trees and shrubs occurring in Australia and South-East Asia. The 'tea tree' oil available in the Netherlands is distilled from the Melaleuca alternifolia and mainly contains eucalyptol. Eucalyptol is probably the most important allergen.

Adult↗

Ingestion of tea tree oil (Melaleuca oil) by a 4-year-old boy.

A 4-year-old boy ingested a small quantity of tea tree oil. Within 30 minutes, he became ataxic and shortly thereafter progressed to unresponsiveness; he was endotracheally intubated by paramedics. His neurologic status improved gradually over 10 hours, and he remains well on follow-up. Tea tree oil is an increasingly popular topical antiseptic that is available in a wide variety of products, often without warning labels. Healthcare providers should be aware of the common uses of tea tree oil, as well as its potential toxicity.

Accidents, Home↗

Antifungal activity of the components of Melaleuca alternifolia (tea tree) oil.

AIMS: To investigate the in vitro antifungal activity of the components of Melaleuca alternifolia (tea tree) oil. METHODS AND RESULTS: Activity was investigated by broth microdilution and macrodilution, and time kill methods. Components showing the most activity, with minimum inhibitory concentrations and minimum fungicidal concentrations of < or =0.25%, were terpinen-4-ol, alpha-terpineol, linalool, alpha-pinene and beta-pinene, followed by 1,8-cineole. The remaining components showed slightly less activity and had values ranging from 0.5 to 2%, with the exception of beta-myrcene which showed no detectable activity. Susceptibility data generated for several of the least water-soluble components were two or more dilutions lower by macrodilution, compared with microdilution. CONCLUSIONS: All tea tree oil components, except beta-myrcene, had antifungal activity. The lack of activity reported for some components by microdilution may be due to these components becoming absorbed into the polystyrene of the microtitre tray. This indicates that plastics are unsuitable as assay vessels for tests with these or similar components. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has identified that most components of tea tree oil have activity against a range of fungi. However, the measurement of antifungal activity may be significantly influenced by the test method.

Acyclic Monoterpenes↗

Antiviral activity of Australian tea tree oil and eucalyptus oil against herpes simplex virus in cell culture.

The antiviral effect of Australian tea tree oil (TTO) and eucalyptus oil (EUO) against herpes simplex virus was examined. Cytotoxicity of TTO and EUO was evaluated in a standard neutral red dye uptake assay. Toxicity of TTO and EUO was moderate for RC-37 cells and approached 50% (TC50) at concentrations of 0.006% and 0.03%, respectively. Antiviral activity of TTO and EUO against herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2) was tested in vitro on RC-37 cells using a plaque reduction assay. The 50% inhibitory concentration (IC50) of TTO for herpes simplex virus plaque formation was 0.0009% and 0.0008% and the IC50 of EUO was determined at 0.009% and 0.008% for HSV-1 and HSV-2, respectively. Australian tea tree oil exhibited high levels of virucidal activity against HSV-1 and HSV-2 in viral suspension tests. At noncytotoxic concentrations of TTO plaque formation was reduced by 98.2% and 93.0% for HSV-1 and HSV-2, respectively. Noncytotoxic concentrations of EUO reduced virus titers by 57.9% for HSV-1 and 75.4% for HSV-2. Virus titers were reduced significantly with TTO, whereas EUO exhibited distinct but less antiviral activity. In order to determine the mode of antiviral action of both essential oils, either cells were pretreated before viral infection or viruses were incubated with TTO or EUO before infection, during adsorption or after penetration into the host cells. Plaque formation was clearly reduced, when herpes simplex virus was pretreated with the essential oils prior to adsorption. These results indicate that TTO and EUO affect the virus before or during adsorption, but not after penetration into the host cell. Thus TTO and EUO are capable to exert a direct antiviral effect on HSV. Although the active antiherpes components of Australian tea tree and eucalyptus oil are not yet known, their possible application as antiviral agents in recurrent herpes infection is promising.

Antiviral Agents↗

Tea tree oil: a systematic review of randomized clinical trials.

AIM: Tea tree oil (TTO) is immensely popular for various topical applications. In vitro studies have repeatedly demonstrated that it has antibiotic activity. This article is an attempt to systematically review the evidence from randomised clinical trials for or against effectiveness of external TTO in dermatological conditions. METHODS: Six electronic databases were searched. Methodological quality was assessed by Jadad score. Data were extracted and validated in a standardised fashion by two independent reviewers. RESULTS: Only 4 trials were located. They suggest that TTO may be effective as a treatment of acne and fungal infections. The evidence is promising but by no means compelling. The adverse effects of TTO are usually mild and transient. They mainly consist of allergic reactions. CONCLUSIONS: It is concluded that, so far, there is no compelling evidence to show that TTO is efficacious in any dermatological condition. However, in view of promising findings, TTO deserves to be investigated more closely.

Administration, Topical↗

In vitro activity of lysostaphin, mupirocin, and tea tree oil against clinical methicillin-resistant Staphylococcus aureus.

Colonization of methicillin-resistant Staphylococcus aureus (MRSA) commonly leads to infection by the same strain. We examined the activity of lysostaphin, mupirocin, and tea tree oil against clinical MRSA (n = 98) isolates. MIC(50) (range) were as follows: lysostaphin, 0.125 mg/L (0.125-0.25); mupirocin, 0.5 mg/L (0.19-1024); tea tree oil, 1024 mg/L (512-2048). High- and low-level mupirocin resistance was noted in 9.2% of our MRSA isolates. Time kill results indicate MRSA activity at 24 h was lysostaphin = gentamicin = vancomycin (P mupirocin > tea tree oil (P >or= .05). Checkerboard testing indicated a synergistic relationship between lysostaphin and mupirocin in combination with gentamicin. Antagonism was observed with the combination of vancomycin and tea tree oil; time kill studies confirmed this result. Decolonization options are limited and resistance to mupirocin exists. Lysostaphin and tea tree oil may offer additional therapeutic options for the decolonization of MRSA where current treatment alternatives are limited.

Anti-Bacterial Agents↗

Treatment of toenail onychomycosis with 2% butenafine and 5% Melaleuca alternifolia (tea tree) oil in cream.

The prevalence of onychomycosis, a superficial fungal infection that destroys the entire nail unit, is rising, with no satisfactory cure. The objective of this randomized, double-blind, placebo-controlled study was to examine the clinical efficacy and tolerability of 2% butenafine hydrochloride and 5% Melaleuca alternifolia oil incorporated in a cream to manage toenail onychomycosis in a cohort. Sixty outpatients (39 M, 21 F) aged 18-80 years (mean 29.6) with 6-36 months duration of disease were randomized to two groups (40 and 20), active and placebo. After 16 weeks, 80% of patients using medicated cream were cured, as opposed to none in the placebo group. Four patients in the active treatment group experienced subjective mild inflammation without discontinuing treatment. During follow-up, no relapse occurred in cured patients and no improvement was seen in medication-resistant and placebo participants.

Administration, Topical↗

Does tea tree oil have a place in the topical treatment of burns?

Burnaid is a sorbalene-based cream containing 40 mg/g of tea tree oil and 1 mg/g of triclosan. This investigation was carried out to determine the effect of Burnaid, a commercial tea tree oil preparation, against Enterococcus faecalis (ATCC29212), Staphylococcus aureus (ATCC29213), Escherichia coli (ATCC25922), and Pseudomonas aeruginosa (ATCC27853), with the activity of the base product in the commercial preparation. The organisms were suspended in sterile saline (0.5 McFarland Standard) and inoculated onto horse blood agar (E. faecalis and S. aureus) or Mueller-Hinton agar (E. coli and P. aeruginosa). One hundred microliters of Burnaid unsterilized, Burnaid sterilized and the base product (Tinasolve) were placed in duplicate in wells cut into the agar plates. Sterility and inactivation cultures were also performed on the samples. None of the samples were found to be contaminated with bacteria prior to testing. Only S. aureus and E. coli showed zones of growth inhibition around the Burnaid and Tinasolve. Zones of growth inhibition (22 mm) were similar for the active product (Burnaid) and the base (Tinasolve). There was no activity against E. faecalis or P. aeruginosa. In view of our findings and literature indicating the cytotoxicity of tea tree oil against human fibroblasts and epithelial cells, it is recommended that this product should not be used on burn wounds.

Anti-Infective Agents, Local↗

Inhibition of acetylcholinesterase by Tea Tree oil.

Pediculosis is a widespread condition reported in schoolchildren. Treatment most commonly involves the physical removal of nits using fine-toothcombs and the chemical treatment of adult lice and eggs with topical preparations. The active constituents of these preparations frequently exert their effects through inhibition of acetylcholinesterase (AChE, EC 3.1.1.7). Increasing resistance to many preparations has led to the search for more effective treatments. Tea Tree oil, otherwise known as Melaleuca oil, has been added to several preparations as an alternative treatment of head lice infestations. In this study two major constituents of Tea Tree oil, 1,8-cineole and terpinen-4-ol, were shown to inhibit acetylcholinesterase at IC50 values (inhibitor concentrations required to give 50% inhibition) of 0.04 and 10.30 mM, respectively. Four samples of Tea Tree oil tested (Tisserand, Body Treats, Main Camp and Irish Health Culture Association Pure Undiluted) showed anticholinesterase activity at IC50 values of 0.05, 0.10, 0.08 and 0.11 microL mL(-1), respectively. The results supported the hypothesis that the insecticidal activity of Tea Tree oil was attributable, in part, to the anticholinesterase activity of Tea Tree oil.

Acetylcholine↗

Antifungal effect of Australian tea tree oil on Malassezia pachydermatis isolated from canines suffering from cutaneous skin disease.

The lipophilic yeast Malassezia pachydermatis is part of the normal skin flora of most warm-blooded organisms. In a number of surveys it could be demonstrated that this yeast species might be involved in different skin diseases like seborrhoeic dermatitis, especially in dogs and cats. In order to look for an alternative therapeutic agent to the commonly used antimycotic and antiseptic synthetic substances the in vitro activity of Australian tea tree oil, the essential oil of Melaleuca alternifolia, against several strains of Malassezia pachydermatis was examined. All tested strains showed remarkably high susceptibility to tea tree oil. With these results the excellent antibacterial activity of tea tree oil is extended to a new group of fungal pathogens colonizing mainly mammals' skin. During the last ten years there was an increasing popularity of tea tree oil containing human health care products. The presented data open up new horizons for this essential oil as a promising alternative agent for topical use in veterinary medicine as well.

Animals↗

Topical use of tea tree oil reduces the dermal absorption of benzoic acid and methiocarb.

Tea tree oil (TTO) is a complex mixture of terpene hydrocarbons. Intensive topical use of TTO in different cosmetics and investigations into its potential as an antimicrobial or anti-inflammatory agent has accentuated the need for studies on the toxicity of TTO. We have applied an experimental in vitro model using static diffusion cells with human skin to study penetration characteristics of terpinen-4-ol and the way TTO affects the barrier integrity of the skin and the percutaneous penetration of two chemicals covering a range of solubilities from 0.03 g/l (methiocarb) to 3.0 g/l (benzoic acid). Through GC-MS analysis we identified the major constituents of TTO. In our experimental set-up with full-thickness skin, only the least lipophilic ingredients of TTO penetrated the skin. Barrier integrity was evaluated through measurement of percutaneous penetration of tritiated water. Data indicate that 1% TTO does not affect barrier conditions. The Kp value for tritiated water was increased significantly at 5% TTO, which demonstrate that the barrier integrity is affected at this relatively low concentration of TTO. The barrier integrity is, however, not seriously damaged, but our data indicate an initiated and concentration-dependent effect on the barrier integrity. TTO changed the penetration characteristics for benzoic acid as well as for methiocarb. The general effect was that TTO reduced the maximal flux. For methiocarb, the lag-time was also prolonged by increasing the TTO concentration in the donor phase to 5%. Thus, TTO reduced the overall amount of benzoic acid as well as methiocarb entering the receptor chamber.

Administration, Topical↗

Effect of Australian tea tree oil on the viability of the wall-less bacterium Mycoplasma pneumoniae.

In vitro assays using a variety of essential oils revealed a particularly high antibacterial effect of Australian tea tree oil (TTO) on a great number of gram-negative and gram-positive bacteria of unrelated phylogenetic origin. In the present study, the susceptibility of cell wall-less bacteria such as the human pathogenic bacterium Mycoplasma pneumoniae to Australian tea tree oil was examined. The minimum inhibitory concentration (MIC) was determined to be 0.006% (v/v) TTO for the wild type and to 0.003% (v/v) TTO for mutants of M. pneumoniae which lost the ability to adhere to host cells (cytadherence-negative). The MIC and the MBC (minimum bactericidal concentration) for M. pneumoniae are 100 times lower than those for all other eubacteria tested. Electron microscopy with negatively stained cells as well as with ultrathin sections revealed a tendency to ovoid or round cells after oil treatment whereas the untreated cells of the wild type exhibit a flask-shaped morphology with a tip-like structure at one pole of the cell. The integrity of the mycoplasmal membrane seems not to be affected by TTO since no leakage of the Mycoplasma cell was observed after oil treatment. In the HET-CAM test TTO did not show any visible signs of irritation in concentrations less than 25%. Although the active component in TTO that has anti-mycoplasmal activity is not known, it seems very promising to use TTO tentatively for mouth washing and inhalation in case of Mycoplasma-pneumoniae-infection.

Animals↗

Melaleuca alternifolia (tea tree) oil inhibits germ tube formation by Candida albicans.

The effect of tea tree oil (TTO) on the formation of germ tubes by Candida albicans was examined. Two isolates were tested for germ tube formation (GTF) in the presence of TTO concentrations (% v/v) ranging from 0.25% (1/2 minimum inhibitory concentration [MIC]) to 0.004% (1/128 MIC). GTF at 4 h in the presence of 0.004 and 0.008% (both isolates) and 0.016% (one isolate) TTO did not differ significantly (P > 0.05) from controls. At all other concentrations at 4 h, GTF differed significantly from controls (P < 0.01). A further eight isolates were tested for GTF in the presence of 0.031% TTO, and at 4h the mean GTF for all 10 isolates ranged 10.0-68.5%. Two isolates were examined for their ability to form germ tubes after 1 h of pre-exposure to several concentrations of TTO, prior to induction of germ tubes in horse serum. Cells pre-exposed to 0.125 and 0.25% TTO formed significantly fewer germ tubes than control cells at 1 h (P < 0.05), but only those cells pre-exposed to 0.25% differed significantly from control cells at later time points (P < 0.01). GTF by C. albicans is affected by the presence of, or pre-exposure to, sub-inhibitory concentrations of TTO. This may have therapeutic implications.

Anti-Infective Agents, Local↗