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At least 19 recordsLinked to original sources
PubMed1994

Melaleuca oil (tea tree oil) dermatitis.

BACKGROUND: Melaleuca oil (tea tree oil) is the essential oil distilled from the leaves of Melaleuca alternifolia Cheel. Tea tree oil is popular for treating various cutaneous maladies. OBJECTIVE: Our purpose was to determine which constituent compounds of Melaleuca oil are responsible for allergic contact eczema in seven patients who became sensitized. METHODS: The seven patients were patch tested with Finn Chambers to a 1% solution (vol/vol) of melaleuca oil and 1% solutions (vol/vol) of 11 constituent compounds. RESULTS: Of seven patients reactive to the 1% melaleuca oil solution, six patients also reacted to limonene, five to alpha-terpinene and aromadendrene, 2 to terpinen-4-ol, and one each to p-cymene and alpha-phellandrene. d-Carvone, an autooxidative derivative of limonene, caused no reactions among the seven patients. CONCLUSION: d-Limonene was the most common allergen causing allergic contact eczema in our patients. Clinicians are likely to see more contact eczema caused by the increasing use of this popular nostrum.

Aged↗
PubMed1998

In-vitro activity of essential oils, in particular Melaleuca alternifolia (tea tree) oil and tea tree oil products, against Candida spp.

The in-vitro activity of a range of essential oils, including tea tree oil, against the yeast candida was examined. Of the 24 essential oils tested by the agar dilution method against Candida albicans ATCC 10231, three did not inhibit C. albicans at the highest concentration tested, which was 2.0% (v/v) oil. Sandalwood oil had the lowest MIC, inhibiting C. albicans at 0.06%. Melaleuca alternifolia (tea tree) oil was investigated for activity against 81 C. albicans isolates and 33 non-albicans Candida isolates. By the broth microdilution method, the minimum concentration of oil inhibiting 90% of isolates for both C. albicans and non-albicans Candida species was 0.25% (v/v). The minimum concentration of oil killing 90% of isolates was 0.25% for C. albicans and 0.5% for non-albicans Candida species. Fifty-seven Candida isolates were tested for sensitivity to tea tree oil by the agar dilution method; the minimum concentration of oil inhibiting 90% of isolates was 0.5%. Tests on three intra-vaginal tea tree oil products showed these products to have MICs and minimum fungicidal concentrations comparable to those of non-formulated tea tree oil, indicating that the tea tree oil contained in these products has retained its anticandidal activity. These data indicate that some essential oils are active against Candida spp., suggesting that they may be useful in the topical treatment of superficial candida infections.

Antifungal Agents↗
PubMedDate not supplied

A study of tea tree oil ototoxicity.

Tea tree oil shows promise as an effective treatment for a number of micro-organisms commonly associated with otitis externa and otitis media, but its possible ototoxicity has not been previously assessed. The ototoxicity of tea tree oil was examined in the guinea pig by measuring the thresholds of the compound auditory nerve action potential (CAP) to tone bursts before and after instillation of the oil into the middle ear. After 30 min of instillation, 100% tea tree oil caused a partial CAP threshold elevation at 20 kHz. A lower concentration of oil [2% tea tree oil dissolved in saline using 0.5% detergent (Tween-80)] did not cause any significant lasting threshold change after middle ear instillation for the same period of time. The latter concentration of oil is greater than the minimum inhibitory concentration reported for most micro-organisms in the effective spectrum of the oil and this suggests that this concentration may be safe and effective provided only short exposures (about 30 min) are used. The results suggest that high concentrations of tea tree oil applied to the round window for a relatively short time are to some extent ototoxic to the high-frequency region of the cochlea. Hence further study is needed to establish whether tea tree oil can be used with safety in the treatment of external and middle ear infections.

Animals↗
PubMed1998

Tea tree oil allergy: what is the offending agent? Report of three cases of tea tree oil allergy and review of the literature.

Tea tree oil is currently enjoying popularity as a 'cure-all' for a variety of skin conditions, from infections to psoriasis, and many household and personal products containing Melaleuca oil are available. However, despite its chemical complexities and enthusiastic use, there have been only a few reports of allergic reactions to tea tree oil. 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. Because patients often neglect to mention that they have used 'natural' remedies, it is important that physicians are aware of the potential adverse effects of these products. Furthermore, identification of the allergenic ingredients in tea tree oil may assist the growing industry to produce safer products.

Adult↗
PubMed2000

The mode of antimicrobial action of the essential oil of Melaleuca alternifolia (tea tree oil).

The essential oil of Melaleuca alternifolia (tea tree) exhibits broad-spectrum antimicrobial activity. Its mode of action against the Gram-negative bacterium Escherichia coli AG100, the Gram-positive bacterium Staphylococcus aureus NCTC 8325, and the yeast Candida albicans has been investigated using a range of methods. We report that exposing these organisms to minimum inhibitory and minimum bactericidal/fungicidal concentrations of tea tree oil inhibited respiration and increased the permeability of bacterial cytoplasmic and yeast plasma membranes as indicated by uptake of propidium iodide. In the case of E. coli and Staph. aureus, tea tree oil also caused potassium ion leakage. Differences in the susceptibility of the test organisms to tea tree oil were also observed and these are interpreted in terms of variations in the rate of monoterpene penetration through cell wall and cell membrane structures. The ability of tea tree oil to disrupt the permeability barrier of cell membrane structures and the accompanying loss of chemiosmotic control is the most likely source of its lethal action at minimum inhibitory levels.

Anti-Bacterial Agents↗
PubMed1996

Antifungal activity of the essential oil of Melaleuca alternifolia (tea tree oil) against pathogenic fungi in vitro.

The in vitro antifungal activity of tea oil, the essential oil of Melaleuca alternifolia, has been evaluated against 26 strains of various dermatophyte species, 54 yeasts, among them 32 strains of Candida albicans and other Candida sp. as well as 22 different Malassezia furfur strains. Minimum inhibitory concentrations (MIC) of tea tree oil were measured by agar dilution technique. Tea tree oil was found to be able to inhibit growth of all clinical fungal isolates. For the investigated dermatophytes MIC values from 1,112.5 to 4,450.0 micrograms/ml with a geometric mean of 1,431.5 micrograms/ml were demonstrated. Both C. albicans strains and the other strains belonging to the genus Candida and Trichosporon appeared to be slightly less susceptible to tea tree oil in vitro. However, their MIC values, which varied from 2,225.0 to 4,450.0 micrograms/ml (geometric mean 4,080 micrograms/ml), indicated moderate susceptibility to the essential oil of M. alternifolia. The lipophilic yeast M. furfur seemed to be most susceptible to tea tree oil. MIC values between 556.2 and 4,450.0 micrograms/ml (geometric mean 1,261.5 micrograms/ml) were found against the tested M. furfur strains. However, when calculated as percentage tea tree oil of the agar, the above-mentioned concentrations correspond to 0.5-0.44% tea tree oil content. These values are far below the usual relatively high therapeutic concentrations of the agent; approximately 5-10% solution or even the concentrated essential oil are used for external treatment. In comparison with tea tree oil, in vitro susceptibility against miconazole, an established topical antifungal, was tested. As expected, very low MIC values for miconazole were found for dermatophytes (geometric mean 0.2 microgram/ml), yeasts (geometric mean 1.0 microgram/ml), and M. furfur (geometric mean 2.34 micrograms/ml). It is suggested that the in vivo effect of tea tree oil ointment in the therapy of fungal infections of the skin and mucous membranes as well as in the treatment of dandruff, a mild form of seborrheic dermatitis, may be at least partly due to an antifungal activity of tea tree oil.

Antifungal Agents↗
PubMed2000

Terpinen-4-ol, the main component of the essential oil of Melaleuca alternifolia (tea tree oil), suppresses inflammatory mediator production by activated human monocytes.

OBJECTIVE AND DESIGN: To evaluate potential antiinflammatory properties of tea tree oil, the essential oil steam distilled from the Australian native plant, Melaleuca alternifolia. MATERIAL AND METHODS: The ability of tea tree oil to reduce the production in vitro of tumour necrosis factor-alpha (TNFalpha), interleukin (IL)-1beta, IL-8, IL-10 and prostaglandin E2 (PGE2) by lipopolysaccharide (LPS)-activated human peripheral blood monocytes was examined. RESULTS: Tea tree oil emulsified by sonication in a glass tube into culture medium containing 10% fetal calf serum (FCS) was toxic for monocytes at a concentration of 0.016% v/v. However, the water soluble components of tea tree oil at concentrations equivalent to 0.125% significantly suppressed LPS-induced production of TNFalpha, IL-1beta and IL-10 (by approximately 50%) and PGE2 (by approximately 30%) after 40 h. Gas chromatography/mass spectrometry identified terpinen-4-ol (42 %), a-terpineol (3 %) and 1,8-cineole (2%, respectively, of tea tree oil) as the water soluble components of tea tree oil. When these components were examined individually, only terpinen-4-ol suppressed the production after 40 h of TNFalpha, IL-1beta, IL-8, IL-10 and PGE2 by LPS-activated monocytes. CONCLUSION: The water-soluble components of tea tree oil can suppress pro-inflammatory mediator production by activated human monocytes.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1995

Broth micro-dilution method for determining the susceptibility of Escherichia coli and Staphylococcus aureus to the essential oil of Melaleuca alternifolia (tea tree oil).

A broth micro-dilution method was used to examine the susceptibility of Escherichia coli (n = 110) and Staphylococcus aureus (n = 105) to the essential oil of Melaleuca alternifolia (tea tree oil). The detergent Tween 80 was used successfully to enhance the solubility of tea tree oil in the test medium. The MIC90 of tea tree oil for E. coli was 0.25% while for S. aureus it was 0.50%.

Escherichia coli↗
PubMed2000

Time-kill studies of tea tree oils on clinical isolates.

Tea tree oil has recently emerged as an effective topical antimicrobial agent active against a wide range of organisms. Tea tree oil may have a clinical application in both the hospital and community, especially for clearance of methicillin-resistant Staphylococcus aureus (MRSA) carriage or as a hand disinfectant to prevent cross-infection with Gram-positive and Gramnegative epidemic organisms. Our study, based on the time-kill approach, determined the kill rate of tea tree oil against several multidrug-resistant organisms, including MRSA, glycopeptide-resistant enterococci, aminoglycoside-resistant klebsiellae, Pseudomonas aeruginosa and Stenotrophomonas maltophilia, and also against sensitive microorganisms. The study was performed with two chemically different tea tree oils. One was a standard oil and the other was Clone 88 extracted from a specially bred tree, which has been selected and bred for increased activity and decreased skin irritation. Our results confirm that the cloned oil had increased antimicrobial activity when compared with the standard oil. Most results indicated that the susceptibility pattern and Gram reaction of the organism did not influence the kill rate. A rapid killing time (less than 60 min) was achieved with both tea tree oils with most isolates, but MRSA was killed more slowly than other organisms.

Anti-Infective Agents, Local↗
PubMed2000

The outer membrane of Pseudomonas aeruginosa NCTC 6749 contributes to its tolerance to the essential oil of Melaleuca alternifolia (tea tree oil).

Pseudomonas aeruginosa is less susceptible to the antimicrobial properties of tea tree oil than many bacteria and its tolerance is considered to be due to its outer membrane. Polymyxin B nonapeptide (PMBN), which has no antibacterial action, was used to permeabilize the outer membrane. The addition of PMBN to Ps. aeruginosa NCTC 6749 markedly increased this organism's susceptibility to tea tree oil and to its normally inert hydrocarbons, p-cymene and gamma-terpinene.

Anti-Infective Agents, Local↗
PubMed1996

Susceptibility of transient and commensal skin flora to the essential oil of Melaleuca alternifolia (tea tree oil).

OBJECTIVES: The purpose of this study was to determine the susceptibility of a range of transient and commensal skin flora to the essential oil of Melaleuca alternifolia, or tea tree. METHODS: A modified broth microdilution method was used. Polyoxyethylene sorbitan mono-oleate detergent was added to the test medium to enhance solubility of the tea tree oil. RESULTS: Serratia marcescens had the lowest minimum inhibitory concentration (MIC90) of 0.25%. The highest MIC90 was 3% for Pseudomonas aeruginosa. The lowest minimum bactericidal concentration (MBC90) was 0.25% for S. marcescens and Klebsiella pneumoniae, whereas the highest was 8% for Staphylococcus capitis. CONCLUSIONS: S. aureus and most of the gram-negative bacteria tested were more susceptible to tea tree oil than the coagulase-negative staphylococci and micrococci. These results suggest that tea tree oil may be useful in removing transient skin flora while suppressing but maintaining resident flora.

Gram-Negative Bacteria↗
PubMed1999

Degradation products of monoterpenes are the sensitizing agents in tea tree oil.

BACKGROUND: Patients using tea tree oil (TTO) topically may become sensitized to this natural remedy. More than 30 cases have been documented in the literature since 1991. OBJECTIVE: Freshly distilled, as well as oxidized TTO, some fractions, and single constituents were used for experimental sensitization in guinea pigs. TTO was stored on a window sill to study the influence of light, oxygen, and warmth. The oxidized oil and different fractions were devoted to experimental sensitization in guinea pigs to determine their sensitizing potency. Fifteen constituents were patch tested in TTO-sensitive patients to find how many may play a role as contact allergens. METHODS: Guinea pigs were sensitized by a modified FCA-method (Freund's complete adjuvant) with freshly distilled TTO, oxidized TTO, the monoterpene and sesquiterpene fraction, and 1, 8-cineole. TTO-sensitive patients were tested with 15 typical constituents and degradation products. Gas chromatographic analysis was used to detect degradation products of the deteriorated TTO. RESULTS: Fresh TTO was revealed to be a very weak sensitizing material whereas oxidized TTO was 3 times stronger. The monoterpene fraction showed to be a stronger sensitizer than the sesquiterpene fraction. All 11 patients reacted mostly with a ++-plus or even a -plus reaction to alpha-terpinene, terpinolene and ascaridol. alpha-Phellandrene became positive in four patients, myrcene in only two. Gas chromatographic analyses showed that the formation of peroxides increased within 4 days from less than 50 to more than 500 ppm. Peroxides, epoxides and endoperoxides were formed. Deterioration products of alpha-terpinene were found to be mainly p-cymene, ascaridol, isoascaridol, a ketoperoxide, and colorless crystals that likely were 1,2,4-trihydroxy menthane. The p-cymene content increased dramatically from 2% to 11.5%. alpha- and gamma-terpinene, as well as terpinolene, were reduced to one half of their former concentration. Ascaridol and isoascaridol have never before been found in TTO. CONCLUSION: Tea tree oil kept in open and closed bottles or other containers undergoes photooxidation within a few days to several months, leading to the creation of degradation products that are moderate to strong sensitizers. Peroxides, epoxides and endoperoxides, like ascaridol and 1,2,4-trihydroxy menthane, are formed. These must be considered responsible for the development of allergic contact dermatitis seen in individuals treating themselves with the oil. A test series with 15 characteristic constituents is recommended for patch testing.

Adult↗
PubMed1998

1998 William J. Stickel Bronze Award. Antifungal activity of Melaleuca alternifolia (tea-tree) oil against various pathogenic organisms.

Tea-tree oil (oil of Melaleuca alternifolia) has recently received much attention as a natural remedy for bacterial and fungal infections of the skin and mucosa. As with most naturally occurring agents, claims of effectiveness have been only anecdotal; however, several published studies have recently demonstrated tea-tree oil's antibacterial activity. This study was conducted to determine the activity of tea-tree oil against 58 clinical isolates: Candida albicans (n = 10), Trichophyton rubrum (n = 8), Trichophyton mentagrophytes (n = 9), Trichophyton tonsurans (n = 10), Aspergillus niger (n = 9), Penicillium species (n = 9), Epidermophyton floccosum (n = 2), and Microsporum gypsum (n = 1). Tea-tree oil showed inhibitory activity against all isolates tested except one strain of E floccosum. These in vitro results suggest that tea-tree oil may be useful in the treatment of yeast and fungal mucosal and skin infections.

Antifungal Agents↗
PubMed1992

Tea tree oil in the treatment of tinea pedis.

Tea tree oil (an essential oil derived primarily from the Australian native Melaleuca alternifolia) has been used as a topical antiseptic agent since the early part of this century for a wide variety of skin infections; however, to date, the evidence for its efficacy in fungal infections is still largely anecdotal. One hundred and four patients completed a randomized, double-blind trial to evaluate the efficacy of 10% w/w tea tree oil cream compared with 1% tolnaftate and placebo creams in the treatment of tinea pedis. Significantly more tolnaftate-treated patients (85%) than tea tree oil (30%) and placebo-treated patients (21%) showed conversion to negative culture at the end of therapy (p < 0.001); there was no statistically significant difference between tea tree oil and placebo groups. All three groups demonstrated improvement in clinical condition based on the four clinical parameters of scaling, inflammation, itching and burning. The tea tree oil group (24/37) and the tolnaftate group (19/33) showed significant improvement in clinical condition when compared to the placebo group (14/34; p = 0.022 and p = 0.018 respectively). Tea tree oil cream (10% w/w) appears to reduce the symptomatology of tinea pedis as effectively as tolnaftate 1% but is no more effective than placebo in achieving a mycological cure. This may be the basis for the popular use of tea tree oil in the treatment of tinea pedis.

Adolescent↗
PubMed1998

Effects of tea tree oil on Escherichia coli.

Tea tree oil (TTO) stimulates autolysis in exponential and stationary phase cells of Escherichia coli. Electron micrographs of cells grown in the presence of TTO showed the loss of electron dense material, coagulation of cell cytoplasm and formation of extracellular blebs. Stationary phase cells demonstrated less TTO-stimulated autolysis and also had greater tolerance to TTO-induced cell death, compared to exponentially grown cells. It was also revealed that subpopulation of stationary phase cells demonstrated increased tolerance to TTO-bactericidal effects.

Bacteriolysis↗
PubMed2000

Allergic contact dermatitis to tea tree oil with erythema multiforme-like id reaction.

The commercial production of tea tree oil, extracted from Melaleuca alternifolia Cheel, has considerably increased over the past 15 years in response to a strong demand for natural remedies and aromatic substances. The number of case reports that describe allergic contact dermatitis (ACD) to this essential oil is also on the rise. We report an additional case of ACD to tea tree oil that presented with an extensive erythema multiforme-like reaction. A skin biopsy was performed from a targetlike lesion distant from the site of the initial dermatitis. The patient was treated with systemic and topical corticosteroids. Five months later, he was patch tested to the North American standard series, to his own tea tree oil, to a fresh batch of tea tree oil, and to some related allergens. The skin biopsy showed a spongiotic dermatitis without histological features of erythema multiforme. Patch testing elicited a 3+ reaction to old, oxidized tea tree oil, a 2+ reaction to fresh tea tree oil, a 2+ reaction to colophony, a 1+ reaction to abitol, and a 1+ reaction to balsam of Peru. We believe this is the first report of erythema multiforme-like reaction secondary to ACD from tea tree oil. Other interesting features are the stronger reaction to oxidized than to fresh tea tree oil, and concomitant reactivity to colophony, abitol, and balsam of Peru.

Allergens↗
PubMed1996

Toxic effects of some conifer resin acids and tea tree oil on human epithelial and fibroblast cells.

The present study was undertaken to assess and compare the in vitro cytotoxic effects of three resin acid analogues: dehydrobietic acid, podocarpic acid, O-methylpodocarpic acid; an essential oil from Australia (tea tree oil); and tapped oleoresin from Thailand, on human epithelial and fibroblast cells, using a quantitative neutral red spectrophotometric assay. All of the investigated compounds except for tea tree oil exhibited a cytotoxic activity which was proportional to their concentrations and time of exposure up to 24 h, i.e. higher concentrations and longer time of exposure caused increased cell death. Dehydroabietic acid and the oleoresin were the most toxic compounds followed by O-methylpodocarpic acid, whereas podocarpic acid and tea tree oil showed a lower level of toxicity. On the basis on these findings it is concluded that an isopropyl group on the aromatic C-ring is of great importance for the cytotoxicity of the tested abietane resin acids, thus indicating that the cytotoxic activity of oleoresins most probably is caused by synergistic or additive effects of resin acids. The results from this work support the view that antibacterial activity parallels cytotoxic activity which suggests a similar mode of action, most probably exerted by membrane-associated reactions.

Abietanes↗