The concept of using smells to affect one's health has been around since the ancient Egyptians and Greeks. Today, a small minority of people - mostly Westerners - swear by the health benefits of aromatherapy to cure a variety of ailments.
Since the commercial industry for aromatherapy has grown significantly in the past few decades, scientists are interested to find out if the therapy has any effects, based on a host of biochemical markers.
The researchers, from Ohio State University, found that two popular scents - lemon and lavender - failed to produce any biological effects. The scientists checked subjects' immune status, wound healing ability, pain control, and stress relief ability, and found no correlation between the smells and these factors. Based on three psychological tests, lemon did appear to enhance mood, but lavender had no effect on mood.
Very few scientific studies have investigated the medical impact of aromatherapy. The treatment is perceived differently in various parts of the world. In France, for example, some essential oils are administered by doctors and regulated as prescription drugs. However, in the United States, Russia, Germany, Japan and other nations, aromatherapy has never been recognized as a valid branch of medicine.
Proponents of aromatherapy claim that the scents work by two mechanisms: the influence of aroma on the brain's limbic system, and the direct pharmacological effects of essential oils, such as when rubbed on the skin.
In the Ohio State study, 56 volunteers participated in tests where cotton balls laced with lemon oil, lavender oil, or distilled water were taped below their noses. Then, the participants underwent pain tests such as having tape applied and removed from the skin, and their feet immersed in 32-degree F water.
The researchers monitored the participants' blood pressure and heart rate during the experiments, and took regular blood samples from each volunteer. The scientists found no changes in levels of the cytokines Interleukin-6 and Interleukin-10, nor stress hormones such as cortisol, norepinephrine, and other catacholomines - biochemical markers that would signal effects on both the immune and endocrine system.
"This is probably the most comprehensive study ever done in this area, but the human body is infinitely complex," explained Internal Medicine Professor William Malarkey, one of the researchers. "If an individual patient uses these oils and feels better, there's no way we can prove it doesn't improve that person's health.
"But, we still failed to find any quantitative indication that these oils provide any physiological effect for people in general."
The study is published in the journal Psychoneuroendocrinology.
via: Ohio State University