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Tea tree oil: a potential alternative for the management ofmethicillin-resistant Staphylococcus aureus (MRSA)



Complementary and alternative medicines occupy a privileged marketing position in many countries, including Australia, being able to carry low-level health claims while being relatively unfettered by regulatory requirements. Consequently, many enjoy widespread use for therapeutic purposes in the absence of definitive efficacy or safety data. Occasionally, the therapeutic properties of complementary and alternative medicines are scrutinised more closely and more thoroughly than their conventional counterparts, leading to the confirmation or discrediting of their properties.
Australian Infection
Tea tree oil:
potential alternative for the management
Staahvlococcus auvew
BSc(Hons), PhD
BSc, PGDip, PhD
Syndie Messagev
BSc, PhD
BAppSc, MAppEpid, PhD, FRCPath,
Microbiology, School of Biomedical
Chemical Sciences
The University of Western Australia, Crawley, WA
Division of Microbiology
Infectious Diseases
The Western Australian Centre for Pathology
Research, Nedlands, WA
major components terpinen-4-01, a-terpinene and y-terpinene
that collectively comprise approximately 70% of the whole oil,
Complementary and alternative medicines occupy a privileged and delineates many of the physical characteristics such as
marketing position in many countries, including Australia, being relative density, refractive index and optical rotation.
able to carry low-level health claims while being relatively
unfettered by regulatory requirements. Consequently, many Notably, no specifications regarding the required levels of
enjoy widespread use
therapeutic purposes in the absence of biological activity have been set, in part because these are still
definitive efficacy or safety data. Occasionally, the therapeutic being
Part there
comDlementarv and alternative medicines
evidence that the biological activities of oils that meet the
international standard vary significantly. However, as the
biological properties of tea tree oil become increasingly well-
conventional counterparts, leading to the confirmation or characterised and any potential for variation becomes apparent,
discrediting of their properties. this may become necessary.
While the scientific investigation of complementary and In contrast to the apparent robustness of the biological properties
alternative medicines is at a nascent stage in Australia, certain
being investigated One
formulation of tea tree oil into ~roducts ma" dramaticallv affect
essential oil of
Melaleuca altemfolia,
also known as tea tree or its biological with
oil. Produced from steam distilled from the foliage of to compromise its antimicrobial activity5.
this Australian native ~lant. tea tree oil has been vromoted since
the 1920s as an antiseptic and disinfectant, more eifective and less
established biological property of the oil, with activity
corrosive than the gold standard of the day, phenol or carbolic demonstrated against bacteria
and viruses IJ. Other
Its popularity dwindled during the era surrounding the biological properties described include anti-inflammatory
discovery and development of penicillins, and recurred only pr~perties'~,'%nd, possibly, anti-tumoural activity
relatively recently during the natural product renaissance of the
late 1970s and 1980s. Today tea tree oil is available in many
cosmetic and toiletry products as well as a range of therapeutic
Originally harvested from natural bush stands of
M. alternifolia,
tea tree oil is now produced on large-scale plantations, primarily
in north-eastern New South Wales. The physical and chemical
properties of tea tree oil may vary from batch to batch and are
influenced by many factors, including provenance, cultivation
conditions, production processes and storage conditions
Quality control of these properties of this oil has been greatly
assisted by the development of an international standard for tea
tree oil3. The standard dictates compositional limits for
of the
approximately 100 terpene components of the oil, including the
Activity against methicillin-resistant
Staphylococcus auveus
The first suggestion that tea tree oil may have had clinically
useful antimicrobial activity against MRSA was made in 1987 by
Longstaff '"ho reported that these bacteria were
susceptible to the oil. No additional characterisation occurred
until 1995 when Carson
et al.
tested the susceptibility of
isolates of MRSA (32 mupirocin-resistant) and found them
uniformly susceptible, with MICs around 0.25% and MBCs of
0.5%. Several other groups have corroborated this activity '"',
leading to speculation that tea tree oil may be a useful agent for
the decolonisation of MRSA carriage or the treatment of skin
wounds infected with MRSA.
Australian Infection Control
Some clinical data to support this hypothesis came from a pilot
study in which the efficacy of a 4% tea tree oil nasal ointment and
a 5% tea tree oil body wash was compared to conventional
treatment of mupirocin nasal ointment and Triclosan skin wash
for the decolonisation of MRSA in hospital inpatients
small study, in which there were 15 patients in each group, did
not show a significant difference between the two treatment
groups; five patients and two patients were cleared, while three
and eight remained colonised in the tea tree oil and conventional
treatment groups, respectively. Five patients from the
conventional treatment group and seven from the tea tree oil
group did not complete the course of treatment. Use of the tea
tree oil nasal ointment resulted in reports of adverse events
ranging from mild swelling of the nasal mucosa to burning on
application, but no patient numbers were given. No adverse
events were recorded for either the tea tree oil body wash or the
mupirocin nasal ointment, and one patient complained of skin
tightness after using the Triclosan body wash.
Additional evidence that tea tree oil warrants further
consideration for MRSA decolonisation came from a larger study
in which 236 MRSA-positive patients were randomly assigned to
a standard treatment or tea tree oil treatment regimen26. The
standard treatment was a 4% chlorhexidine gluconate soap
applied all over the body at least once a day and 2% mupirocin
nasal ointment applied to the anterior nares three times a day,
combined with 1% silver sulfadiazine cream applied to skin
lesions, leg ulcers and wounds once a day. A 5% tea tree oil soap
and a 10% tea tree oil cream for anterior nares and skin lesions,
leg ulcers and wounds comprised the tea tree oil regimen. The
application frequency was the same as for the standard treatment
regimen and both regimens were used for 5 days. Swabs to test
for clearance were taken
days and 14 days after treatment
completion in 224 patients and the outcomes
these patients
were evaluated. While mupirocin was significantly better than
tea tree oil at eradicating nasal carriage, tea tree oil was
significantly better for skin sites. Overall, there was no
significant difference in the treatment regimens and no adverse
effects were reported in either treatment group.
Sporadic reports of the successful treatment of MRSA infections
by products containing tea tree oil have also appeared in the
literature. A mixture of plant extracts, including tea tree oil, was
used in the treatment of previously intractable MRSA
o~teomyelitis~~ with apparent success.
The formulation issues mentioned previously hold particular
relevance for the future clinical evaluation of tea tree oil
products. We have recently assessed the antibacterial activity of
tea tree oil and tea tree oil products using the EN 1276 and EN
12054 European suspension test methods4. The tea tree oil
products evaluated were a hygienic skin wash (HSW) and an
alcoholic hygienic skin wash (AHSW), both containing 5% tea
tree oil, and an alcoholic hand rub (AHR) containing 3% tea tree
oil. These formulations were assessed in perfect conditions using
the EN 12054 test, and in perfect conditions as well as in the
presence of interfering substances with the EN 1276 test, against
aureus, Acinefobacfer baumannii, Escherichia coli
With the EN 1276 test, the AHR achieved a 25 loglo reduction
against all the test organisms within
minute contact time. The
AHSW achieved this reduction with
A. baumannii
contact time and against the remaining test organisms after 5
minute contact time. Using the
12054 test, after
contact time, 5% tea tree oil in 0.001% Tween 80 and the AHSW
achieved a reduction in
P. aeruginosa
concentrations in
excess of 4 loglo, while the AHR achieved this reduction against
all of the test organisms. In comparison, the HSW generally
required longer contact times to achieve smaller reductions in
test organism concentrations.
Oil concentrations and products that passed the European
suspension test guidelines were subsequently evaluated
in vivo
using the European handwashing method (EN 1499) as well as
using freshly excised human skin samplesz8. Data from both
in vivo
ex vivo
methods indicated that 5% tea tree oil in
0.001% Tween 80 and the AHSW were significantly more active
than the non-medicated soft soap control after
minute of
handwashing or rubbing.
and toxicity
Just as clinical data to support the use of tea tree oil and tea tree
oil products in the management of MRSA colonisation and
infection are scarce, so too are safety and toxicity data for the oil.
While the anecdotal data from 80 years of use suggest that the
topical application of tea tree oil is safe, this is not a substitute for
empirical safety data. Some formal toxicity studies have been
conducted" but more are required. Most published reports of
adverse reactions discuss irritant and allergic skin reactions to the
although cases of poisoning in children 31~3%nd adults
have occurred. Since tea tree oil is toxic if ingested and should
only be used topically, formal studies of its acute and chronic
effects on skin remain a priority.
Despite these limitations, the data from
in vitro
in vivo
reported to date provide a strong impetus for comprehensively
assessing the efficacy of tea tree oil in the management of MRSA
colonisation and/or infection. However, the question of who
would fund and conduct the required studies is a vexed one.
The fact that tea tree oil may be efficacious in the management of
MRSA but may not be validated due to a lack of financial support
highlights a critical issue in the future evaluation of many
complementary and alternative medicines. Unless novel
strategies that foster the rigorous evaluation of complementary
and alternative medicines and allow investors to reap the
commercial benefits of such work or substantial non-commercial
funding sources become available, complementary and
alternative medicines will remain largely uninvestigated.
Vol10 Issue
March 2005
Australian Infection Control
Some initiatives to address this dilemma have begun. In 1992,
the National Institutes of Health in the USA created an Office of
Alternative Medicine and provided it with a budget of US$2
million. This agency has since become the National Center for
Complementary and Alternative Medicine and has an operating
budget in 2005 of US$123 million. In 1999, the Therapeutic
Goods Administration in Australia established an Office of
Complementary Medicines; however, it has no budget for
Ultimately, given the right circumstances, sufficient information
will be available to resolve the validity of the claims made for tea
tree oil. Whatever the outcome of current and future work, the
whole process will hopefully broaden our outlook and serve as a
template for the investigation of other complementary and
alternative medicines.
1. Carson CF
Riley TV. Antimicrobial activity of the essential oil of
Melaleuca alternifolia
[review]. Lett Appl Microbiol 1993; 16:49-55.
2. Brophy JJ, Davies NW, Southwell IA, Stiff IA
Williams LR. Gas
chromatographic quality control for oil of
type (Australian tea tree). J Agric Food Chem 1989; 37:1330-1335.
3. International Organisation or Standardisation IS0 4730:2004. Oil of
terpinen-4-01 type (tea tree oil). Geneva, Switzerland:
International Organisation for Standardisation, 2004.
4. Messager S, Hammer KA, Carson CF
Riley TV. Assessment of the
antibacterial activity of tea tree oil using the European EN 1276 and
EN 12054 standard suspension tests. J Hosp Infect 2005; 59:113-125.
5. Hammer KA, Carson CF
Riley TV. Influence of organic matter,
cations and surfactants on the antimicrobial activity of
(tea tree) oil in vitro. J Appl Microbiol 1999; 86:446-452.
6. Carson CF, Hammer KA
Riley TV. Broth micro-dilution method
for determining the susceptibility of
Escherichia coli
Staphylococcus aureus
to the essential oil of
Melaleuca alternifolia
tree oil). Microbios 1995; 82:181-185.
7. Hammer KA, Carson CF
Riley TV. Susceptibility of transient and
commensal skin flora to the essential oil of
Melaleuca alternifolia
tree oil). Am
Infect Control 1996; 24:186-189.
8. Griffin SG, Markham JL
Leach D. An agar dilution method for
the determination of the minimum inhibitory concentration of
essential oils. J Essential Oil Res 2000; 12:249-255.
9. Banes-Marshall L, Cawley P
Phillips CA.
In uitro
activity of
Melaleuca alternifolia
(tea tree) oil against bacterial and
isolates from clinical specimens. Brit J Biomed Sci 2001; 58:139-145.
10. Nenoff P, Haustein U-F
Brandt W. Antifungal activity of the
essential oil of
Melaleuca alternifolia
(tea tree oil) against pathogenic
fungi in vitro. Skin Pharmacol 1996; 9:388-394.
11. Hammer KA, Carson CF
Riley TV.
In vitro
susceptibility of
Malassezia furfur
to the essential oil of
Melaleuca alternifolia.
J Med
Vet Mycol 1997; 35375-377.
12. Hammer
Carson CF
Riley TV.
In vitro
activity of essential
oils, in particular
Melaleuca alternifolia
(tea tree) oil and tea tree oil
products, against
spp. J Antimicrob Chemother 1998;
13. Hammer KA, Carson CF
Riley TV. In vitro activity of
(tea tree) oil against dermatophytes and other
filamentous fungi. J Antimicrob Chemother 2002; 50:195-199.
14. Schnitzler P, Schon K
Antiviral activity of Australian
tea tree oil and eucalyptus oil against herpes simplex virus in cell
culture. Pharmazie 2001; 56:343-347.
Brand C, Ferrante A, Prager RH, Riley TV, Carson CF, Finlay-Jones
Hart PH. The water soluble-components of the essential oil of
Melaleuca alternifolia
(tea tree oil) suppress the production of
superoxide by human monocytes, but not neutrophils, activated in
vitro. Inflamm Res 2001; 50:213-219.
Pearce AL, Satkunanathan N, Storer
Finlay-Jones JJ
Hart PH. Regulation of wheal and flare by tea tree oil:
complementary human and rodent studies.
Invest Dermatol2004;
Calcabrini A, Stringaro A, Toccacieli L, Meschini S, Marra M,
Colone M, Salvatore
Mondello F, Arancia
Molinari A.
Terpinen-4-01, the main component of
Melaleuca alternifolia
(tea tree)
oil Inhibits the in vitro growth of human melanoma cells. J Invest
Dermatol2004; 122:349-360.
Walsh LJ
Longstaff J. The antimicrobial effects of an essential oil
on selected oral pathogens. Periodontol 1987; 8:ll-15.
Carson CF, Cookson BD, Farrelly HD
Riley TV. Susceptibility of
Staphylococcus aureus
to the essential oil of
Melaleuca alternifolia.
J Antimicrob Chemother 1995; 35:421-424.
Nelson RRS. In-vitro activities of five plant essential oils against
methicillin-resistant Staphylococcus aureus and vancomycin-
Enterococcus faecium
[letter]. J Antimicrob Chemother 1997;
Chan CH
Loudon KW. Activity of tea tree oil on methicillin-
Staphylococcus aureus
(MRSA) [letter]. J Hosp Infect 1998;
Elsom GKF
Hide D. Susceptibility of methicillin-resistant
Staphylococcus aureus
to tea tree oil and mupirocin. J Antimicrob
Chemother 1999; 43:427-428.
May J, Chan CH, King A, Williams L
French GL. Time-kill studies
of tea tree oils on clinical isolates. J Antimicrob Chemother 2000;
Hada T, Furuse S, Matsumoto
Hamashima H, Masuda K,
Shiojima K, Arai
Comparison of the effects
in uitro
of tea tree oil and plaunotol on methicillin-susceptible and
methicillin-resistant strains of
Staphylococcus aureus.
2001; 106:133-141.
Caelli M, Porteous J, Carson CF, Heller R
Tea tree oil as
an alternative topical decolonization agent for methicillin-resistant
Staphylococcus aureus.
Hosp Infect 2000; 46:236-237.
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; 56:283-
Sherry E, Boeck H
Warnke PH. Topical application of a new
formulation of eucalyptus oil phytochemical clears methicillin-
Staphylococcus aureus
infection. Am J Infect Control 2001;
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; 59:220-228.
Carson CF, Riley TV
Cookson BD. Efficacy and safety of tea tree
oil as a topical antimicrobial agent. J Hosp Infect 1998; 40:175-178.
Carson CF
Riley TV. Safety, efficacy and provenance of tea tree
(Melaleuca alternifolia)
oil. Contact Dermatitis. 2001; 45:65-67.
Jacobs MR
Hornfeldt CS.
oil poisoning.
Toxicol Clin
Toxicol 1994; 32:461-464.
Del Beccaro MA.
oil poisoning in a 17-month-old. Vet
Hum Toxicol 1995; 37:557-558.
Morris MC, Donoghue A, Markowitz JA
Osterhoudt KC.
Ingestion of tea tree oil
oil) by a 4-year-old boy. Pediatr
Emerg Care 2003; 19:169-171.
Elliott C. Tea tree oil poisoning. Med J Aust 1993; 159330-831.
Seawright A. Tea tree oil poisoning
Comment. Med J Aust 1993;
Vol 10 Issue 1 March 2005
... Tea Tree Oil (TTO, Tea tree oil) is an essential oil obtained by steam distillation from the leaves of Melaleuca alternifolia (Myrtaceae) that grows naturally in Australia. Studies have shown that tea tree oil has a broad-spectrum antimicrobial activity with its high terpinen-4-ol content (Carson et. al, 2005). In Turkey, as in Europe and North America it has also begun to be used in various cosmetic preparations and care products. In recent years, tea tree oil has been described as a safe antiseptic, more preferred due to its natural origin. TTO is regarded as an ideal disinfectant for topical use due to its antimicrobial effect against a wi ...
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The increasing need of natural antimicrobial agents has started a new field of investigation due to the global diseases. Synthetic antimicrobial agents are found to be causing skin problems and other toxic effects in long term. Therefore, antimicrobial activity of three natural extracts tea tree oil, tree moss extract, oakmoss extract and organic o-phenylphenol were evaluated in the study. These agents were added to a bar soap formulation and tested for antimicrobial activity EN 1276 standard method. The agents were added to five bar soap formulation as i) bar soap base; ii) bar soap base and tea tree oil; iii) bar soap base, tea tree oil, tree moss extract and oakmoss extract; iv) bar soap base, and o-phenylphenol; v) bar soap base, tea tree oil, tree moss extract, oakmoss extract and o-phenylphenol were prepared. As a result, in formulation (i) bar soap could not only pass the antibacterial test. The maximum antimicrobial activity was seen in formulation (v).
... Tea tree (Melaleuca alternifolia) oil (TTO) is known since long for many remedial uses and has been claimed as a potential candidate to replace antibiotics particularly in topical applications (Carson et al., 2006). Early studies on the antimicrobial activity of TTO claimed that TTO to be more active against antibiotic-resistant bacteria (Carson et al., 2005). Furthermore, it is added as an active constituent in many topical formulations used for the treatment of cutaneous infections for controlling dandruff, acne, lice, herpes and other skin infections (Pazyar et al., 2013). ...
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The unceasing emerging of multidrug-resistant bacteria imposes a global foremost human health threat and discovery of new alternative remedies are necessity. The use of plant essential oil in the treatment of many pathogenic bacteria is promising. Acne vulgaris is the most common skin complaint that fears many people about their aesthetic appearance. In this work we investigated the antibacterial activity of some plant oils against acne-inducing bacteria. Three bacterial isolates were identified from Egypt, biochemically and by means of 16s rRNA gene typing, and were designated as Staphylococcus aureus EG-AE1, Staphylococcus epidermidis EG-AE2 and Cutibacterium acnes EG-AE1. Antibiotic susceptibility test showed resistance of the isolates to at least six antibiotics, yet they are still susceptible to the last resort Vancomycin. In vitro investigations of eleven Egyptian plant oils, identified tea tree and rosemary oils to exhibit antibacterial activity against the antibiotic-resistant acne isolates. Inhibition zones of 15 ± 0.5, 21.02 ± 0.73 and 20.85 ± 0.76 mm was detected when tea tree oil applied against the above-mentioned bacteria respectively, while inhibition zones of 12.5 ± 1.5, 15.18 ± 0.38 and 14.77 ± 0.35 mm were detected by rosemary oils. Tea tree and rosemary oils exhibited bacteriostatic and bactericidal activity against all the strains with MICs/MBCs ranging between 39-78 mg/L for tea tree oil and 39–156 mg/L for rosemary oil. All the isolates were killed after 4 and 6 h upon growing with 200 mg/L of tea tree and rosemary oils, respectively. Additionally, gas chromatography mass spectrometry (GC/MS) profiling identified and detected a variable number of antimicrobial compounds in both oils.
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Detailed GC and GC-MS analyses of oil of Melaleuca have identified several constituents not previously reported from Melaleuca alternifolia and clarified some earlier assignments. The range, mean, and coefficient of variation for the principle constituents in 800 typical samples are presented along with the compositions of several substandard oils. Isolation and storage procedures affecting the chemical composition of the oil are reported. Ethanolic extraction of mature leaves gave solutions suitable for direct injection into a gas chromatograph for the qualitative determination of tea tree oil. Comparison with conventional steam distillation showed that this technique was suitable for preliminary analysis of tea tree oil yield and quality.
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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%.
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All 66 isolates of Staphylococcus aureus tested were susceptible to the essential oil of Melaleuca alternifolia, or tea tree oil, in disc diffusion and modified broth microdilution methods. Of the isolates tested, 64 were methicillin-resistant S. aureus (MRSA) and 33 were mupirocin-resistant. The MIC and MBC for 60 Australian isolates were 0·25% and 0·50%, respectively. Comparable results were obtained by co-workers in Britain using similar methods. These in-vitro results suggest tea tree oil may be useful in the treatment of MRSA carriage.
Methods for the measurement of the minimum inhibitory concentration (MIC) of antibacterial agents have been developed for water-soluble substances and require adaptation for use with water-insoluble essential oils. This paper reports a standardized agar dilution MIC method, using 0.5% v/v Tween 20 as a dispersant, which provides a reliable and reproducible technique. The method was tested using two Melaleuca alternifolia oil samples with two different levels of terpinen-4-ol (37% and 45% v/v). The MIC values of the tea tree oil samples against a wide selection of bacteria, moulds and yeast are reported.
Melaleuca alternifolia has been used for medical purposes since Australia was colonized in 1788. Melaleuca alternifolia is commonly called tea tree, although this vernacular name is also given to many other species in the Leptospermum and Melaleuca genera. A small tree, it grows up to 5 m in height, has papery bark and narrow, tapered leaves up to 20 mm in length and flowers in summer. Melaleuca alternifolia is unique to Australia and its natural habitat is a relatively small area around the Clarence and Richmond rivers in the north-east coastal area of New South Wales where the terrain is generally low lying and swampy. The essential oil of M. alternifolia, or tea tree oil. has enjoyed increased medicinal use in recent years. It is a pale yellow viscous liquid with a distinctive pungent odour and is composed of a complex mixture of monoterpenes, 1-terpinen-4-ol, cineole and other hydrocarbons (Peña 1962).
Tea tree oil, or the essential oil of Melaleuca alternifolia, is becoming increasingly popular as a naturally occurring antimicrobial agent. The antimicrobial activity of eight components of tea tree oil was evaluated using disc diffusion and broth microdilution methods. Attempts were also made to overcome methodological problems encountered with testing compounds which have limited solubility in aqueous media. After assessing media with and without solubilizing agents, the disc diffusion method was used to determine the susceptibility of a range of micro-organisms to 1,8-cineole, 1-terpinen-4-ol, ρ-cymene, linalool, α-terpinene, γ-terpinene, α-terpineol and terpinolene. While the disc diffusion method lacked reproducibility, it was considered useful as a procedure for screening for antimicrobial activity. Terpinen-4-ol was active against all the test organisms while ρ-cymene demonstrated no antimicrobial activity. Linalool and α-terpineol were active against all organisms with the exception of Pseudomonas aeruginosa. Minimum inhibitory and minimum cidal concentrations of each component against Candida albicans, Escherichia coli and Staphylococcus aureus were determined using a broth microdilution method. Modifications to this method overcame solubility and turbidity problems associated with the oil components and allowed the antimicrobial activity of each of the components to be quantified reproducibly. There was reasonable agreement between minimum inhibitory concentrations and zones of inhibition. These results may have significant implications for the future development of tea tree oil as an antimicrobial agent.
A 23-month-old boy became confused and was unable to walk thirty minutes after ingesting less than 10 mL of T36-C7, a commercial product containing 100% melaleuca oil. The child was referred to a nearby hospital. His condition improved and he was asymptomatic within 5 hours of ingestion. He was discharged to home the following day. Melaleuca oil, extracted from the Melaleuca alternifolia, contains 50-60% terpenes and related alcohols. Clinical experience with products containing melaleuca oil is limited. This case report suggests that ingestion of a modest amount of a concentrated form of this oil may produce signs of toxicity.
Ingestion of significant quantities of Melaleuca oil or Australian tea tree oil has been described only once in the medical literature. This report describes a 17-mo-old male who ingested less than 10 ml of the oil and developed ataxia and drowsiness. Emergency physicians, poison control personnel and pediatricians should be aware of potential toxicity from this product.
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. 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. 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. 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.