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An evaluation of tea tree oil as an alternative microbicide

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VOL: 101, ISSUE: 11, PAGE NO: 32

Mick Willcox, BN, is an army staff nurse, Queen Alexandra Hospital, Portsmouth

Tea tree oil is used as a complementary treatment for many conditions, and is widely used in the beauty industry (Box 1). As nurses we have a remit to understand complementary therapies and inform patients of the choices available if they so wish.

Tea tree oil is used as a complementary treatment for many conditions, and is widely used in the beauty industry (Box 1). As nurses we have a remit to understand complementary therapies and inform patients of the choices available if they so wish.

The literature search
A search of the BNI, CIHNAL, Medline and TRIP databases, combined with a simple search on the internet, revealed many articles on tea tree oil.

A review of the literature highlighted contact dermatitis as a potential side-effect and the potential uses of tea tree oil in treating dermatological conditions, toenail infections, oral and vaginal candidiasis and methicillin-resistant Staphylococcus aureus (MRSA). Clinical research is limited and is at an early stage, but in-vitro results provide strong evidence on which to base further research in humans.

Nearly all the published work found on tea tree oil comes from, or is based on, results from the department of microbiology at the University of Western Australia. This is not to detract from the vigour or accuracy of their work, but suggests the need for further research from different specialist areas, and independent trials.

Background
The use of antibiotics in combating bacterial infection is well proven. However, the development of new antibiotics to keep pace with the rapid evolution of antibiotic resistance in bacteria is proving very difficult.

If antibiotics are not to become obsolete a change in attitudes to the treatment of bacterial infections is needed. Women seem to be particularly concerned about antibiotic therapies and problems such as candidiasis post antibiotic treatment. Research reveals there is significant demand for natural remedies (Perrett et al, 2003) and indicates a growing use of unproven complementary therapies (Pirotta et al, 2003).

Tea tree oil is used in complementary medicine as an antiseptic, antibacterial and antifungal topical application. It has also been used to good effect in orthopaedic surgery to treat bone infected with MRSA (Sherry et al, 2001). Tea tree oil has also been used on wounds and skin infections, toenail infections and thrush.

Unfortunately, it has also been shown to cause contact dermatitis in some patients, with reactions mainly related to the strength of the application (Satchell, 2002). However, the percentage of patients who have a reaction is relatively low.

There has also been a reported case of a systemic reaction (Mozelsio et al, 2003), and a reaction in a child who ingested tea tree oil (Morris et al, 2003) but these seem to be isolated cases.

Dermatological uses
At this stage there is little advice on how tea tree oil should be used on wounds, but a cautious approach should be adopted in order to prevent over-application and tissue damage.

Ernst et al (2002) suggest that there is 'no compelling evidence' for the effectiveness of tea tree oil. However, Koh et al (2002) have shown experimentally that tea tree oil can reduce histamine-induced skin inflammation. This claim is anecdotally supported by the heavy use of tea tree oil in the beauty industry to reduce inflammation and redness and prevent infection following cosmetic procedures such as waxing and the removal of unwanted hair. There are also numerous tea tree oil products on the market that claim to help reduce spots and cleanse skin.

In other more rigorous research tea tree oil was shown to be effective against Staphylococcus aureus and most gram-negative bacteria, while not as effective against skin flora such as staphylococci and micrococci bacteria (Hammer et al, 1996).

This suggests that the oil may be useful for removing transient skin flora, while only suppressing normal skin flora. So the prospects for using tea tree oil to kill potentially dangerous bacteria in wounds and other skin conditions look promising. However, as yet properly controlled trials from which to develop evidence-based treatments are lacking.

Toenail infections
In the treatment of fungal toenail infections, a randomised controlled trial found some evidence that butenafine cream in combination with tea tree oil, versus a placebo, significantly improves cure rates at 16 and 36 weeks (Syed et al, 1999).

These findings suggest that tea tree oil could be effective for use with fungal toenail infections.

Another study showed that the mycological cure rate in such infections was 64 per cent in an application that was 50 per cent tea tree oil, compared with 31 per cent in the placebo group. In this study four per cent of patients developed moderate to severe dermatitis. However, the condition improved quickly when use of the tea tree oil preparation was stopped (Satchell et al, 2002). Despite the small incidence of contact dermatitis, tea tree oil has shown good initial results.

Candidiasis
The area that seems to show the most promising results so far is in the treatment of candidiasis. In vitro, tea tree oil has been found to be active against all strains of azole-susceptible and azole-resistant human pathogenic yeasts (Mondello et al, 2003). Tea tree oil seems to work against Candida albicans, C. glabrata and Saccharomyces cerevisiae by altering the properties of their membranes and compromising membrane-associated functions (Hammer et al, 2003).

Tea tree oil has also been shown to accelerate the clearance of C. albicans from experimentally infected rat vagina (Mondello et al, 2003). In addition, in patients with Aids, an oral solution of tea tree oil appears to be effective against oropharyngeal candidiasis that is refractory to fluconazole (Vazquez and Zawawi, 2002). Unfortunately, the lack of extensive clinical studies precludes recommending tea tree oil to patients for the time being.

MRSA
A very exciting area where tea tree oil could be utilised in the future is in the treatment of MRSA infection. Carson et al (1995) were the first to provide in-vitro results suggesting that tea tree oil could be useful in the treatment of MRSA carriers.

It reported effectiveness in vitro against methicillin-susceptible S. aureus (MSSA) and MRSA at high concentrations with less effective results in preparations with a concentration of tea tree oil below 40mg/ml (Hada et al, 2001). In a study by Caelli et al (2000) a combination of four per cent tea tree oil nasal ointment and four per cent tea tree oil body wash was compared with a treatment of two per cent nasal mupirocin and triclosan bodywash and showed that the tea tree oil performed better. While the trial was too small to draw any firm conclusions, the early indications are very positive. This was an Australian study. The standard treatment for MRSA in the UK is Bactroban (mupirocin), but it is obvious from these results that it is important that further studies be conducted.

High-street preparations
As a complementary medicine, tea tree oil is widely available on the high street and online. It can be found in many hair-care products and soaps, but the labelling of these products provides no information about the percentage of tea tree oil they contain.

There are also many facial washes and 'spot sticks' on the market, but once again their labels do not give the percentage strength and provide little information about application. Worryingly there are also antiseptic creams that contain tea tree oil with very vague accompanying instructions - concentrating mostly on how to open the containers - and again no percentage strengths are provided.

Bottles of essential oils (100 per cent tea tree oil) come with cautions about causing skin irritation, but very little information on how to use the product properly. General information is given such as 'add 5-6 drops to a bath', 'apply 1-2 drops to a cotton bud' or 'apply as required'.

One tea tree oil toothpaste proclaims the effectiveness of tea tree oil in reducing plaque, which it has been proved not to do, and yet makes no mention of its possible use in oral candidiasis. Internet sites selling tea tree oil, particularly websites run by manufacturers in Australia, give far more information on use, strength and indications for use, and apart from the sales pitch seem fairly well informed.

Conclusion
If we are to prevent antibiotics becoming less and less effective, the need for alternatives is clear. Preliminary research has shown that tea tree oil has many potential uses, but larger trials are required in order to prove its value beyond doubt.

What is evident is that tea tree oil is showing promise for use in dermatological conditions and in candida and other fungal infections. Possibly the most exciting development is in the treatment of MRSA. Dermatitis caused by tea tree oil is a concern, but this side-effect may be reduced by further work to determine the optimum strength of application.

From a nursing perspective, when helping patients to make informed choices about complementary medications, advice should be as comprehensive as possible, including warnings about the limitations of labelling when buying preparations. However, if tea tree oil is to become a useful resource in the treatment of MRSA and other skin conditions, the most important issue at present is the need for more research.

- This article has been double-blind peer-reviewed.

For related articles on this subject and links to relevant websites see www.nursingtimes.net

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