Can essential oils be used to battle MRSA?
BACKGROUND
Essential oils, also called volatile oils, are a class of products made from many different plants. To make them, steam is passed through the plant material and the vapours collected and condensed. The resulting liquid separates into a water layer and the oil.
The term “essential” refers to the oil having the distinctive scent, or essence, of the plant. Although essential oils are often spoken of as a group, their name highlights that each one is unique and has distinct components and effects. Essential oils have long been used for their different scents in the perfume and cosmetic industry.
The advent of a modern medical crisis has generated more interest. An article in the New England Journal of Medicinecalled antibiotic-resistant superbugs such as MRSA "a clinical super-challenge". All around the world, hospitals and doctors are struggling to respond to several microbes which are resistant to antibiotics. MRSA (methicillin-resistant Staphylococcus aureus) is the best known, but others exist such as vancomycin-resistant enterococci (VRE), multi-resistant salmonellae, and multi-resistant Mycobacterium tuberculosis.
The search is now on for treatments and strategies to deal with this problem. Old antibiotics are being resurrected, and new ones sought. Other strategies are being pursued, such as prominent hand-cleansing fluids. Others are looking to older ways of dealing with infections. Essential oils have been used for thousands of years, including the treatment of infected battle wounds.
EVIDENCE FROM STUDIES
Antibiotics tend to work by targeting specific mechanisms to knock out in microbes. Bacteria become resistant when they develop ways to block the drug or circumvent its effect. Essential oils have effects on several aspects of microbial growth, which makes it more difficult for the microbes to respond effectively to them.
A small but growing number of studies are producing interesting results. For example, an Australian study found that several essential oils were antibacterial, including against MRSA. They showed that this was not due to the oily liquid, because other oils were not active. Some essential oils were as effective as ethanol, peroxide and other disinfectants. However, the oils of thyme white, lemon, lemongrass and cinnamon were much more active against a wide range of microbes.
Few studies have involved humans, but such research is being conducted. For example, scientists at Manchester Metropolitan University showed that a blend of lemongrass and geranium essential oils was antibacterial against MRSA. When the oil was placed in a sealed box containing MRSA, bacterial growth was reduced by about one-third. They developed a vaporiser to deliver the oil vapours into an office overnight while unoccupied. The number of airborne bacteria in the office was reduced by 89 per cent. Then they used the vaporiser in the burns unit of a Manchester hospital for nine months. They found similar reductions in airborne bacteria and had no MRSA outbreaks while using the vaporiser.
This is one of the few controlled studies in this area, but it adds to several case studies where various essential oils have treated unresponsive infections in some individuals. Dramatic improvements were sometimes reported, but not always.
PROBLEMATIC ASPECTS
One of the challenges with essential oils is their variability. Not only are there many different essential oils, but the oils made from the same plant vary with the country of origin and manufacturer. This makes it difficult to know how much of the oil to use, or which method works best.
RECOMMENDATIONS
Much more research is needed to understand the workings of essential oils and to develop products with known effectiveness. For example, a multi-centre randomised controlled trial is currently being conducted in Belfast to see whether tea tree oil prevents the spread of MRSA in critically ill patients.
Meanwhile, for infections which have proved difficult to treat, localised use of essential oils might be worth investigating. Given the complexity of caring for such infections, this should be discussed with the medical team before being tried.
For more everyday use, little evidence is available for practical guidance. Many different oils have been shown to be antibacterial. In addition to those already mentioned, lavender, sage, eucalyptus and more exotic oils are recommended. While many details remain to be clarified, evidence is growing that there is more to essential oils than a pretty scent.
Dónal O’Mathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University
