General Description

Tea tree (Melaleuca alternifolia) is a small tree native to only one area of the world: the northeast coastal region of New South Wales, Australia. The leaves, the portion of the plant that is used medicinally, are the source of a valuable therapeutic oil. Although there are more than 50 members of the Melaleuca family, the oil from the leaf of M. alternifolia has received the most research attention.

Chemical Composition

Tea tree leaves contain about 1.8% of oil obtained via steam distillation.¹ This oil contains more than 48 compounds, but is chiefly composed of the following²:

• 1-terpinen-4-ol

• 1,8-cineol

• Gamma-terpinene (see Figure 102-1)

• p-cymene

• Other terpenes

FIGURE 102-1 Gamma-terpinene.

The Australian standard (AS 2782-1985) for “Oil of Melaleuca (Terpinen-4-ol type)” sets a minimum content of terpinen-4-ol at 30% and a maximum 1,8-cineol content of 15%.¹

History and Folk Use

The medicinal properties of crushed tea tree leaves were known to the Bundjalung Aborigines of northern New South Wales, Australia. The waters of a lagoon where tea tree leaves had fallen and decayed for hundreds of years were viewed as having tremendous healing properties.¹

The first report of tea tree’s medicinal use appeared in the Medical Journal of Australia in 1930.³ A surgeon in Sydney reported impressive results using a solution of tea tree oil to clean surgical wounds. According to this report³:

The results obtained in a variety of conditions when it (tea tree oil) was first tried were most encouraging, a striking feature being that it dissolved pus and left the surface of infected wounds clean so that its germicidal action became more effective without any apparent damage to the tissues. This was something new, as most efficient germicides destroy tissue as well as bacteria.

During World War II, tea tree oil was issued to soldiers to use as a disinfectant. The Australian Army went so far as to commandeer supplies of the oil and exempt leaf cutters from national service to maintain production. The production of tea tree oil during World War II was regarded as an “essential” industry.¹

After World War II, the tea tree oil industry stagnated for more than 30 years. There were a number of reasons for this, including the general trend away from natural medicines and toward synthetic medical drugs. However, during the late 1970s and early 1980s, the Australian tea tree oil industry was reborn as successful plantations growing M. alternifolia were established.¹

Tea tree oil has been used in the treatment of the following conditions ¹:

A variety of tea tree oil–based cosmetic products exist in the marketplace, including toothpastes, shampoos and conditioners, creams, hand and body lotions, soaps, gels, liniments, and nail polish removers.

Pharmacology

Tea tree oil possesses significant antiseptic properties and is regarded by many as the ideal skin disinfectant. This claim is supported by its efficacy against a wide range of organisms, its good penetration, and its lack of skin irritation.¹ The therapeutic uses of tea tree oil are based largely on its antiseptic and antifungal properties. Bacteria and fungal organisms inhibited by tea tree oil are listed in Tables 102-1 and 102-2.^1,⁴^–⁶

TABLE 102-1 Bacteria Inhibited by Melaleuca alternifolia Oil

BACTERIAL SPECIES	% (vol/vol)
BACTERIAL SPECIES	MIC	MBC
Acinetobacter baumannii	1	1
Actinomyces viscosus	0.6	>0.6
Actinomyces spp.	1	1
Bacillus cereus	0.3
Bacteroides spp.	0.06-0.5	0.06-0.12
Corynebacterium spp.	0.2-2	2
Enterococcus faecalis	0.5->8	>8
E. faecium (vancomycin resistant)	0.5-1	0.5-1
Escherichia coli	0.08-2	0.25-4
Fusobacterium nucleatum	0.6->0.6	0.25
Klebsiella pneumoniae	0.25-0.3	0.25
Lactobacillus spp.	1-2	2
Micrococcus luteus	0.06-0.5	0.25-6
Peptostreptococcus anaerobius	0.2-0.25	0.03->0.6
Porphyromonas endodontalis	0.025-0.1	0.025-0.1
P. gingivalis	0.11-0.25	0.13->0.6
Prevotella spp.	0.03-0.25	0.03
Prevotella intermedia	0.003-0.1	0.003-0.1
Propionibacterium acnes	0.05-0.63	0.5
Proteus vulgaris	0.08-2	4
Pseudomonas aeruginosa	1-8	2->8
Staphylococcus aureus	0.5-1.25	1-2
S. aureus (methicillin resistant)	0.04-0.35	0.5
S. epidermidis	0.45-1.25	4
S. hominis	0.5	4
Streptococcus pyogenes	0.12-2	0.25-4
Veillonella spp.	0.016-1	0.03-1

MBC, minimal bactericidal concentration; MIC, minimum inhibitory concentration.

Data from Carson CF, Hammer KA, Riley TV. Melaleuca alternifolia (tea tree) oil: a review of antimicrobial and other medicinal properties. Clin Microbiol Rev. 2006;19:50-62.

TABLE 102-2 Fungi Inhibited by Melaleuca alternifolia Oil

FUNGAL SPECIES	% (vol/vol)
FUNGAL SPECIES	MIC	MFC
Alternaria spp.	0.016-0.12	0.06-2
Aspergillus flavus	0.31-0.7	2-4
A. fumigatus	0.06->2	1-2
A. niger	0.016-0.4	2-8
Blastoschizomyces capitatus	0.25
Candida albicans	0.06-8	0.12-1
C. glabrata	0.03-8	0.12-0.5
C. parapsilosis	0.03-0.5	0.12-0.5
C. tropicalis	0.12-2	0.25-0.5
Cladosporium spp.	0.008-0.12	0.12-4
Cryptococcus neoformans	0.015-0.06
Epidermophyton flocossum	0.008-0.7	0.12-0.25
Fusarium spp.	0.008-0.25	0.25-2
Malassezia furfur	0.03-0.12	0.5-1.0
M. sympodialis	0.016-0.12	0.06-0.12
Microsporum canis	0.03-0.5	0.25-0.5
M. gypseum	0.016-0.25	0.25-0.5
Penicillium spp.	0.03-0.06	0.5-2
Rhodotorula rubra	0.06	0.5
Saccharomyces cerevisiae	0.25	0.5
Trichophyton mentagrophytes	0.11-0.44	0.25-0.5
T. rubrum	0.03-0.6	0.25-1
T. tonsurans	0.004-0.016	0.12-0.5
Trichosporon spp.	0.12-0.22	0.12

MBC, minimal bactericidal concentration; MIC, minimum inhibitory concentration.

Data from Carson CF, Hammer KA, Riley TV. Melaleuca alternifolia (tea tree) oil: a review of antimicrobial and other medicinal properties. Clin Microbiol Rev. 2006;19:50-62.

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