Antimicrobial the herb and had a doctor



Antimicrobial effects of tea tree
essential oil

A literature review by Aoife O’Toole

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Herbal science 4








Tea tree, microbes, Propionibacterium acnes, skin,


In spite of developments in current technologies,
the healthcare industry is constantly burdened with the fear of microbial
infections. Overusing antibiotics has additionally intensified this difficulty,
causing an increase in the rise of antibiotic-resistant pathogens. Attempts to acquire
novel procedures for regulating microbial infections are very vital. Therefore ,
essential oils such as tea tree oil have arose as new, feasible, and harmless
choices for the handling, and/or abolition of these microbes. Tea tree oil
components are conversed in terms of present usages and upcoming ability as antimicrobials.
They have been in existence for thousands of years and used well before any contemporary
drugs were around. This review attempts to offer an explanation as to how tea
tree essential oil can used be while being harmless and how they should be used
in the future to prevent and treat microbial infections.






Tea tree oil is a prevalent essential oil used typically for
its potent antimicrobial properties. It is volatile as an essential oil, and it
is sourced from an Australian plant called Melaleuca
alternifolia. It is widely exploited to treat a number of conditions. Tea tree oil (TTO) is mostly associated
with skin disorders such as acne, which is caused by a microbe recognized as Propionibacterium acnes. Antibiotics are
usually prescribed to treat this condition though there are now antibiotic
resistant strains present (Coates et al. 2002).

Tea Tree Oil first became known to the western world in around
1732. It was discovered by Captain James Cook when he reached Australia. He discovered
a hot and stimulating tea from the leaves of the Melaleuca Alternifolia tree. It was from this that the plant became
known as “tea tree”. The indigenous Australians at that point in time used it
to heal skin diseases and wounds. When James Cook realised this he went back with
a sample of the herb and had a doctor examine it for its healing possessions.
The doctor confirmed that it had a powerful antiseptic characteristic. Shortly
hereafter, the use of TTO expanded, and it is now well-known worldwide as a non-synthetic
antimicrobial (Halcon et al. 2003).Australia is the only country where Melaleuca Alternifolia breeds so it must
be transferred to various countries.

Tea tree oil is made up of many different biochemical constituents
that give it its antiseptic powers. The four main chemical components of tea
tree oil would be as follows; Terpinen-4-ol, ?-Terpinene, ?-Terpinene and Terpinolene
(see table 1).


Table 1. Approximate
percentages present of different chemical components of TTO


Chemical component

Percentage present(approx.)










The rest is made up of many different components which are
present in smaller amounts. Some other components include ?-Terpineol, ?-Pinene,
Limonene and ?-Cymene. There are approximately 98 different components which
can be present in tea tree essential oil. The strengths of these components
vary from oil to oil. However there are certain standards put in place by the
Australian and International Standards Organizations to ensure value of the oil
i.e. a lowest and highest strength range for each constituent (Halcon et
al.2003). Tea tree oil can come in six different biochemical mixtures. There is
a terpinen-4-ol type which is the one that is produced on a commercial scale, a
terpinolene type, and four 1, 8-cineole types.

As I’ve previously mentioned, the natural antimicrobial effects
of tea tree oil are familiar to people all over the world. In current decades
natural and alternative remedies are becoming more and more popular. This
review compiles current developments in the acceptance of the antimicrobial power
of TTO and its components, as well as clinical efficacy. Specific means of
antimicrobial action are studied and analysed, mainly with regards to skin
bacteria to see if it could be used to replace traditional treatments of
antibiotics and harsh chemicals.






TTO shows antimicrobial action against a large range of
Gram-positive and Gram-negative bacteria, yeasts and fungi (Kulik et al.2000). However
it usually is more active to
Gram-positive than to Gram-negative bacteria. The microbes that will be focused
on in this review are two gram positive microbes that target the skin, Propionibacterium acnes and
methicillin resistant Staphylococcus aureus (MRSA) .We will also look at the fungus athlete’s foot.

Tea-tree oil is a popular component of skin preparations,
and a number of its suggested uses imply an anti-microbial effect (Drury 1991).
Tea-tree oil is recommended for the treatment of acne vulgaris. A study comparing
a tea-tree oil gel to benzoyl peroxide lotion demonstrated the efficiency of
the oil for treating this condition (Bassett et al. 1990). Propionibacterium
acnes and coagulase-negative staphylococci have been implicated in the pathogenesis
of acne vulgaris (Shanson 1989), and it is possible that the oil works by
eradicating these microorganisms from acne wounds. Propionibacterium acnes (P.acnes)
settle on the skin and hair follicles. They are oxygen-tolerant, anaerobic
bacteria that prefer to grow in low oxygen environments. They can develop
sticky lumps known as biofilms that help them to attach to surfaces and regulate
their environment (
In many situations, bacterial biofilms have been proven to add to long term
infections, and could help with the perseverance of P. acnes infection in some individuals. As they are gram positive microbes
they have bulky cell walls that aid with defending them from their surroundings.
Still these thick cell walls let hydrophobic particles pierce the cells without
any difficulty and move through the cell wall and inside to the cytoplasm.
Phenolic compounds work this way and they are present in TTO, showing antimicrobial
action against Gram-positive bacteria such as P.acnes (Nazzaro et al. 2013).

There are plenty of additional gram-positive bacteria that
create infections, such as MRSA. MRSA is a major cause of hospital infections
and is becoming increasingly difficult to combat as is it becoming resistant to
all current classes of antibiotics. Approximately 30% of burn wounds become
colonized by MRSA in hospitals. Alternative therapies are being sought for the
treatment of MRSA and essential oils are of particular interest. TTO is proven
to be effective in treating this antibiotic resistant strain of Staphylococcus; however there are
concerns over its toxicity. Even though essential oils are well recognized for
being antimicrobial, they are very seldom used by medical professionals. This
is mainly because of lack of scientific evidence regarding efficacy. Additionally
common medical care is extremely extensively accessible. Edwards-Jones et al. 2004
conducted a study trying to prove the efficacy of essential oils as
antimicrobial agents. The five oils used in the experiment that was carried out
were tea tree, lavender, geranium, patchouli and citricidal. TTO had the maximum
clearing zone when placed in direct contact with two different strains of Staphylococcus aureus. One of these was the
methicillin resilient strain. Essential oils clearly work, so why aren’t they
being used to treat these bacteria? There is great potential for the use of essential
oils as natural antibiotics to control infections, especially infections of the
skin and to control antibiotic resistant strains of bacteria. If there is no
research done into new antibiotics, by the year 2050 a person will die every
three seconds from a bacterial infection (WHO). Seen as no new antibiotics are
being discovered it is time to start looking at natural alternatives and for
funding to be put into researching essential oils in more detail.

As well as being antibacterial, TTO is also known for its
antifungal properties. TTO is well recognized as being effective in controlling
the fungi that cause athletes foot. The fungus is known as Tinea pedis. It is often found in
people whose feet have come to be really moist from perspiration while enclosed
inside tightfitting shoes. It is infectious and can be disseminated through
infected floors, towels or clothing. In a 1972 study done on various foot
problems, Dr. Walker used tea tree oil in three different formulas to try
combating these problems. To start was unmixed oil, secondly was a mixture of 40%
oil with 10% isopropyl alcohol. This was known as Melasol. Third was 8% oil
with lanolin and chlorophyll and this was in ointment form. 60 people took part
in the experiment. 40 took Melasol, 20 used the ointment and 8 applied the unmixed
oil. The medical care changed from three weeks to four years. Of 68 patients,
58 got alleviation from their foot ailments over a time frame of 6 years. There
are four if not more various fungal diseases associated with athlete’s foot and
each of these display sensitivity to TTO.

Conventional treatments for fungal disease of the nails include;
debridement which is removing alien materials and impaired tissue from the nail,
and also there are topical treatments. This review evaluated the effectiveness of
topical treatments of 1% clotrimazole solution in comparison with 100% TTO for treating
of Tinea unguium which is a fungal infection
of the toenail. In a 6 month
double-blind, multicentre, randomised, controlled trial of 117 people with
a Tinea unguium
infection, patients got twice-daily
treatments of either 1% clotrimazole (CL) solution, which is topical antifungal
drug medication, or 100% (TTO). The fact the trial was double blind meant that
neither group knew the treatment that they were receiving. This help to
eliminate and bias. The fact it was a randomised trial ensured there was no
selection bias from the people who ran the trial.

 Debridement and
clinical evaluation were carried out at 0, 1, 3 and 6 months. Samples were
taken at 0 and 6 months. After 6 months, the both groups were associated based
on culture cure (CL=11%, TTO=18%). Three months on, almost half of both
factions stated that they had persistent positive development. The conclusion
was, even though all ongoing treatments have high reoccurring percentages,
using a topical application along with debridement is a good treatment to start
with. Topical treatment, with regards to the previous two concoctions, provides
benefit in how the nail looks and any symptoms associated with it, while oral treatment
has the limitation of expense and possible severe negative effects. This experiment
supported the requirement to use a strong (in this case 100%) concentration of TTO
to achieve improved short-term and long-term efficiency. In children and people
with sensitive skin, a 70% solution may be superior.




In Vitro


A study done by
Walton et al in 2004 attempted to show the in vitro Sensitivity of Sarcoptes scabiei var hominis to
Terpinen-4-ol. The experiment went as follows. The parts of TTO known as; terpinen-4-ol,
terpineol, and 1,8-cineole were utilized in vitro at concentrations equal to
those in 5% TTO.Terpinen-4-ol makes up 42% of TTO and was utilized at a
concentration of 2.1%, terpineol makes up 3% of TTO and was utilized at a
concentration of 0.15%, and 1,8- cineole makes up 2% of TTO and was utilized at
a concentration of 0.1%.Also, mites were shown to all 3 parts of TTO in a
combined mix and to 5% TTO directly . An ivermectin solution of 100 µg/g was also
used for comparison as well as Emulsifying Ointment. The 5% TTO and active component
terpinen-4-ol were effective in reducing mite survival times. Exact applicable dissimilarity’s
in mite survival graphs were noticed for 5% TTO, terpinen-4-ol, and ivermectin
compared to the control which was Emulsifying Ointment. Variability was
observed in survival rates amongst each part of TTO. 85%of the mites had
deceased after 1 hour when shown to 2.1% terpinen-4-ol. Contrary to this, almost
40% and 60% of mites were still alive following 16 hours of exposure to 0.15% terpineol
and 0.1% 1,8-cineole. It was interesting to see that 60% of mites had deceased after
1 hour of exposure to 5% TTO. There is currently no vaccine for scabies and the
growth of new medicines is scarce. The rise of medicine defiant scabies is a serious
issue for the health of many communities. Examining scabies mite medications
response to various stimuli can help recognize a more practical use of accessible
medications and medication combinations to help decrease the development of
defiance. The data showed in this appraisal shows that TTO might be an active agent
for the curing of scabies, as shown by the speedy in vitro killing time seen.


Kirby Bauer method (disk diffusion). According to a study done by
Carson et al. 1995, all 66 isolates of Staphylococcus aureus tested were
susceptible to TTO in disc diffusion and modified broth microdilution methods.
Of the isolates tested, 64 were MRSA and 33 were mupirocin-resistant. The
minimum inhibitory concentration and the minimum bactericidal concentration for
60 isolates were 0-25% and 0-50%, respectively. Comparable results were
obtained by co-workers using similar methods. These in-vitro results suggest
tea tree oil may be useful in the treatment of MRSA.