Melaleuca alternifolia (Tea Tree)

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Chapter 102 Melaleuca alternifolia (Tea Tree)

Michael T. Murray, ND

Melaleuca alternifolia (family: Myrtaceae)

Common name: tea tree

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.

Clinical Applications

The historical uses of tea tree oil demonstrate its wide range of applications as an antiseptic. Three of the more popular and documented uses are in the treatment of skin infections, vaginal infections, and common foot complaints.

Skin Infections

Tea tree oil is useful in a broad range of dermal infections, not only because of its broad-spectrum antiseptic properties, but also because of its capacity to mix with sebaceous secretions and penetrate the epidermis.

A clinical trial in patients with furuncles demonstrated that tea tree oil encouraged more rapid healing without scarring than was seen in matched control subjects.⁷ Presumably, the positive clinical effects were due to the oil’s germicidal activity against Staphylococcus aureus. Tea tree oil efficiently kills S. aureus in the stationary growth phase and within biofilms, making it a promising tool for S. aureus eradication.⁸ In the clinical trial, the method of application consisted of cleaning the site followed by painting the surface of the furuncle freely with tea tree oil two or three times a day.

For most skin infections, the most effective treatment appears to be direct application of full-strength, undiluted oil at the site of infection. If irritation occurs, diluted preparations may be tried.

Lice Infestations

Pediculosis capitis (head lice infestation) treatment typically involves application of topical insecticides such as a pyrethrin or permethrin. An in vitro study showed that tea tree oil exerted the greatest effect of essential oils tested against head lice.⁹ A clinical study compared the efficacy and safety of three topical pediculicides. A pediculicide containing tea tree and lavender oil was compared with a product containing pyrethrins and piperonyl butoxide; the percentage of subjects who were louse-free one day after the last treatment with the tea tree oil and lavender product was 97.6% (41 of 42 patients) compared with 25% (10 of 40 patients) of those using the product containing pyrethrins and piperonyl butoxide.¹⁰ These clinical results, along with in vitro studies, indicate that products containing tea tree oil are effective alternatives to pyrethrin-based products.

Oral Infections

Tea tree oil was shown to exert significant activity against oral pathogens, both bacterial and fungal, and was suggested to be a suitable alternative to chlorhexidine.¹¹ From a clinical perspective, these effects may best be utilized in the treatment of oral candidiasis (thrush). In one open study, 27 patients with acquired immunodeficiency syndrome (AIDS) and oral candidiasis that was clinically refractory to fluconazole were randomly assigned to receive either an alcohol-based or an alcohol-free melaleuca oral solution four times daily for 2 to 4 weeks. Overall, 60% of patients demonstrated a clinical response to the melaleuca oral solution (seven cases were cured and eight cases clinically improved) at 4-week evaluation.¹²

Tea tree oil appears to be quite useful in oral candidiasis in cancer patients. Often these yeasts are resistant to azole antifungal drugs. In one study, 301 yeasts isolated from the mouths of 199 patients with advanced cancer were shown to be susceptible to tea tree oil, including 41 yeasts that were known to be resistant to both fluconazole and itraconazole.¹³

Dandruff

There is evidence that dandruff appears to be related to the yeast Pityrosporum ovale. Because tea tree oil has antifungal activity against P. ovale, a 4-week study was designed to investigate the efficacy and tolerability of 5% tea tree oil shampoo versus a placebo in 126 male and female patients, aged 14 years and older, with moderate dandruff. The 5% tea tree oil shampoo group showed a 41% improvement in the quadrant-area-severity score, compared with an 11% improvement in the placebo group. Statistically significant improvements were also observed in the total area of involvement score, the total severity score, and the itchiness and greasiness components of the patients’ self-assessments. The scaliness component of patient self-assessment improved but was not statistically significant. There were no adverse effects.¹⁴

Acne

Topical application of tea tree oil is a suitable alternative to benzoyl peroxide preparations. In one study, 124 patients with mild to moderate acne randomly received either a 5% gel of tea tree oil or 5% benzoyl peroxide lotion to be applied topically every day. After 3 months, both treatments produced a significant improvement in the mean number of both noninflamed and inflamed lesions, although with noninflamed lesions, benzoyl peroxide was found to be more effective. An important finding was that there were fewer reports of side effects (dryness, pruritus, stinging, burning, and skin redness) with tea tree oil (44% vs 79%).¹⁵

Common Foot Problems

Tea tree oil, in emollient form (8% tea tree oil) or in solution (40%), can be massaged into the feet daily for the treatment of tinea pedis, foot irritation, and bromhidrosis (severely foul-smelling feet).

One researcher concluded, after 6 years of using different concentrations and preparations, that tea tree oil eradicated or improved the symptoms of tinea pedis when used daily by patients at home.⁴ He also reported that even undiluted forms had little effect on onychomycosis (discussed further in “Fungal Nail Infection”). Diluted tea tree oil in solution was found to reduce foot irritation and promote wound healing with surgical incision in cases of corns, calluses, bunions, and hammer toes, and was extremely effective in diminishing bromhidrosis.

In tinea pedis, one double-blind study found that 10% tea tree oil cream compared quite favorably with the antifungal tolnaftate in relieving symptoms, but was less effective in eliminating the fungi from cultures.⁵ Specifically, both the tea tree group (24 of 37 patients) and the tolnaftate group (19 of 33 patients) showed significant improvement in the four clinical parameters of scaling, inflammation, itching, and burning, but only 30% of the subjects who applied tea tree oil cream tested culture negative, compared with 85% in the tolnaftate group.

In another double-blind trial, 158 patients with tinea pedis were randomly assigned to receive either placebo or 25% or 50% tea tree oil solution.¹⁶ Patients applied the solution twice daily to affected areas for 4 weeks and were assessed after 2 and 4 weeks of treatment. A marked clinical response was seen in 68% of the 50% tea tree oil group and in 72% of the 25% tea tree oil group, compared with 39% in the placebo group. Mycologic cure was assessed by culture of skin scrapings taken at baseline and after 4 weeks of treatment. The mycologic cure rate was 64% in the 50% tea tree oil group compared with 31% in the placebo group. Four (3.8%) patients applying tea tree oil experienced moderate to severe dermatitis that improved quickly upon cessation of the study medication.

Fungal Nail Infection

Fungal nail infections (onychomycosis) are the most common cause of nail disease, affecting approximately 2% to 13% of the population. Standard medical treatments include débridement, topical antifungals, and systemic antifungals. All current therapies have high recurrence rates. Oral therapy has the added disadvantages of high cost and potentially serious adverse effects.

One study compared the efficacy and tolerability of the topical application of 1% clotrimazole (CL) solution with that of 100% tea tree oil for the treatment of toenail onychomycosis.¹⁷ The 117 patients received twice daily applications of either 1% CL solution or 100% tea tree oil for 6 months. Débridement and clinical assessment were performed at 0, 1, 3, and 6 months. Culture specimens were obtained at 0 and 6 months. Each patient’s subjective assessment was also obtained 3 months after the conclusion of therapy. After 6 months of therapy, the two treatment groups were comparable on the basis of culture cure (CL = 11%, tea tree = 18%) and clinical assessment documenting partial or full resolution (CL = 61%, tea tree = 60%). Three months later, about half of each group reported continued improvement or resolution (CL = 55%, tea tree = 56%). These results indicate that topical therapy with tea tree oil, in conjunction with débridement, provides excellent improvement in nail appearance and symptomatology.

Vaginal Infections

Tea tree oil demonstrates germicidal activity against a number of common vaginal pathogens and opportunistic organisms, including Trichomonas vaginalis and Candida albicans.¹⁸

A 40% solution of tea tree oil emulsified with isopropyl alcohol and water was found in a clinical study to be highly effective for the treatment of cervicitis, chronic endocervicitis, trichomonal vaginitis, and vaginal candidiasis.¹⁸ Weekly in-office treatment (usually four to six were necessary) involved thorough washing of the perineum, labia, and vagina with a suitable scrub (the commercial product pHisoHex was used in the study). After drying, the affected areas were washed with a 1% tea tree oil solution. This was followed by insertion of a tampon (three 4 × 4–inch sponges) saturated with the 40% tea tree oil solution. Patients were instructed to remove the tampon after 24 hours.

For infectious processes—trichomonas and candidiasis—daily vaginal douches containing 1 quart of water with a 0.4% concentration of the oil were prescribed. No irritation, burning, or other side effects were reported or observed with either the office applications or the douches.

Dosage

A number of commercial products contain tea tree oil. Tea tree oil can be used as a topical antiseptic for reducing microbial counts in wounds, surgical incisions, and skin and vaginal infections. In addition, tea tree leaves can be used to make teas that may be of benefit in cases of sore throat, tonsillitis, sinus infections, and colitis.

Toxicity

Tea tree oil appears to be extremely safe for use as a topical antiseptic.¹⁹ However, it may cause allergic contact dermatitis in some individuals. During a 3-year period, seven patients were seen in an outpatient dermatology clinic in Kona, Hawaii, for contact dermatitis due to the use of commercially available product containing 100% tea tree oil.²⁰ The patients were treating preexisting skin conditions, which included foot fungus, dog scratches, insect bites, and rashes. All patients presented with an eczematous dermatitis. Patch tests indicated that all patients were sensitive to a 1% solution of tea tree oil. It is recommended that individuals apply the oil to a small area of skin before using tea tree oil for the first time so as to avoid the bother of experiencing contact dermatitis over a larger area.

The oral ingestion of tea tree oil cannot be recommended because it could lead to a toxic reaction. However, folk use suggests that oral ingestion of tea from the leaves is reasonably safe.