A study shows aromatherapy works by triggering the body's healing mechanisms, writes BRIDGET CARTER.
If you thought aromatherapy was all in the mind you were right. A scientific study has shown that sniffing essential oils will stimulate your mind, but only if you believe it will.
The findings add to evidence that much complementary medicine relies on the placebo effect - an improvement brought about by medicine that is prescribed for psychological reasons but which has no active components - and the power of suggestion.
Aromatherapy, used for relaxing and revitalising tired brains, is popular among New Zealanders, who spend about $8 million on aromatherapy products each year, with a typical treatment session costing around $70.
Researchers, led by Dr Josef Ilmberger of the Ludwig-Maxmilians University, Munich, studied the effects of oils used for their "re-energising" properties on 50 volunteers who wore surgical masks.
After researchers sprinkled water on the masks, the volunteers' reaction times to a series of mental tasks were assessed.
Some of the volunteers then had oils such as peppermint, jasmine and ylang-ylang sprinkled on the masks, while the masks of others were sprinkled with water.
Volunteers' reaction times were tested again, showing the essential oils appeared to make no difference to reaction times.
But the volunteers were also asked how stimulating, strong and pleasant they found the oils. Those who rated them highly did show small improvements in their reaction times.
"If people thought an oil was stimulating, they got faster," said Dr Ilmberger. "The effects of essential oils or their components on basic forms of attentional behaviour are mainly psychological."
Aromatherapy uses various treatment methods, including massage, during which oils are rubbed into the skin and absorbed into the blood stream.
Essential oils can also enter the body through inhalation.
When inhaled, odours affect the limbic system in the brain. Euphoric odours stimulate a part of the brain that secretes neurochemicals that act as painkillers, but also induce feelings of well-being.
Aphrodisiac odours such as ylang-ylang stimulate the pituitary gland, which then may secrete endorphins, which can also work as painkillers.
Auckland aromatherapist Fiona McLeod said therapeutic aromatherapy worked through more than just the placebo effect.
She had used aromatherapy on irritable babies, who did not know she was using it on them, and on pets with fleas.
Many oils had antibacterial properties, she said. Other oils contained constituents such as citronella, which could help to repel insects.
"People think aromatherapy just works with smell. It is a lot more involved than that."
Aromatherapy triggered memories that could affect emotions, she said.
Bo Hendgen, the president of the Register of Holistic Aromatherapists and managing director of Absolute Essential, said you could measure the therapeutic effects of a smell by the way it made you feel.
If somewhere smelt bad, you would not go there. But somewhere that you associated with rest and relaxation, such as a cafe with the smell of freshly ground coffee, could make you feel better.
Professor Richard Faull, of Auckland University's School of Medicine, said scientific evidence showed that a stimulating environment and an individual's state of mind could help to fight disease.
"If you believe something is going to help you it improves the chances of it helping you."
Vicki Hyde of the New Zealand Skeptics said the results of the study were not surprising.
"We always say the human mind is a weird and wonderful thing."
But the context of aromatherapy was important. For example, if oils were used with a massage, they would probably be more effective.
Dr Richard Tonkin, president of the Research Council for Complementary Medicine, said the findings did not undermine aromatherapy.
"The problem with the placebo effect is that it is regarded by most people as a nuisance or a fake. But it isn't," he said.
"It is a practical and positive effect that acts by catalysing the self-healing mechanisms within a patient."