Aromatherapy oils have also been found to worsen breathing problems in those with lung disease and to increase symptoms of asthma.
They are meant to soothe aches and pains, relieve stress and induce a sense of relaxation. But aromatherapy oils may in fact do more harm than good, according to scientists.
They have claimed that the extracts – used in baths, massages or burned in rooms – react with the air to produce tiny irritant particles. Researchers found that when the so-called essential oils were used in relaxation spas for massages, the concentration of these potentially harmful particles increased tenfold.
The scientists said that certain chemicals in the oils, called volatile organic compounds, mix with the air to form secondary organic aerosols.These particles irritate the eyes, nose and throat, and are also known to cause headaches, nausea, and damage to the liver and kidneys.
This study only examined the size and number of these particles released when people had massages in spas. However other research has shown they are also produced by burning essential oils in the home or office – although not to the same extent.
Essential oils such as lavender, tea tree, eucalyptus and peppermint are extracted from plants and trees. The oils are thought to have a number of health benefits, including improving the skin, boosting the immune system and helping with sleep.
But the scientists from the Chia-Nan University of Pharmacy and Science, Tainan, Taiwan, warn that the negative effects ‘cannot be neglected’.
The study, published in the journal Environmental Engineering Science, measured the volumes of certain secondary organic aerosols when oils were rubbed in during massages in two spas in Taiwan.
The scientists concluded: ‘As aromatherapy, used by the general public and some health institutes, has become one of the most popular complementary therapies, its impact on indoor air quality and health effects cannot be neglected.
‘Volatile organic compound degradation caused by the reaction of these compounds with ozone present in the air can produce small, ultrafine by-products called secondary organic aerosols which may cause eye and airway irritation.’
They added: ‘We compared secondary organic aerosol levels associated for the various fragrant and herbal essential oils tested and conclude that the layout and ventilation within a particular spa may affect the level of indoor air pollutants produced during massage with aromatherapy.’
In 2007, another group of scientists also from Taiwan showed that burning tea tree, lavender and eucalyptus oils in the office also produced large numbers of these harmful particles. Aromatherapy oils have also been found to worsen breathing problems in those with lung disease and to increase symptoms of asthma. And nurses have reported that they can cause skin burning and rashes – often because people put far too much into their baths or on to their skin.
Sceptics argue that many of the perceived benefits of the oils are caused by a placebo effect – and people just convince themselves they feel calmer and more relaxed. They also say there is little scientific evidence that they can relieve pains, cure wounds or boost immunity.