Nov. 29, 2012 -- A little aromatherapy may relieve stress, but long exposures to vaporized essential oils may actually harm your health, a small new study suggests.
Researchers in Taiwan set up an experiment that was meant to mimic the conditions at a typical spa. They used a vaporizer to fill the air in a closed room with tiny droplets of essential oil of bergamot. Bergamot oil comes from a citrus fruit. It's a common ingredient in perfumes, massage oils, and aromatherapy.
Then they asked 100 healthy, young spa workers to stay in the room for two hours on each of three separate visits. Researchers kept tabs on their heart rates and blood pressures every 15 minutes while they were breathing the vaporized oil.
For the first hour that the study volunteers stayed in the room, their heart rates and blood pressures dropped slightly. But after 75 minutes, the trend reversed. Heart rates and blood pressures began to climb. Average increases were very small, about two points for systolic blood pressure -- the top number -- and about two beats per minutes for heart rate.
The study is published in the European Journal of Preventive Cardiology.
Good Scent, Bad Scent
How could sweet scents cause harm? Researcher Kai-Jen Chuang, PhD, of Taipei Medical University, points out that aromatherapy oils are also volatile organic compounds (VOCs), a kind of indoor air pollution that can irritate the eyes, throat, and lungs.
In a previous study, Chuang says he found hair salon workers exposed to VOCs for more than an hour had increases in indicators of inflammation and oxidative stress in their blood.
"Therefore, overexposure to essential oils may be harmful to cardiovascular health in young, healthy subjects," says Chuang.
Not everyone is convinced that's the case.
Pamela Dalton, PhD, a research scientist at the Monell Chemical Senses Center in Philadelphia, Pa., points out that the study has several flaws that weaken its conclusions.
The first is that it didn't include a control group. A control group would reveal what happened to people who sat in the same size room for two hours without smelling any fragrance.
"You see these subtle changes in blood pressure and heart rate. The fact that as time goes on you see a change in the other direction could be attributed to the aroma, but it could also be that they've been sitting there for two hours and they're getting fidgety and anxious or stressed," Dalton says.
Something else that makes Dalton question the study's conclusions is that the average level of VOCs in the room reached about 80 parts per billion.
"That's a pretty small level," Dalton says, perhaps even too small a concentration to smell.
"To me, it doesn't really demonstrate much either way," she says.
Until a better study is done, Dalton thinks it makes sense for people with preexisting conditions like allergies and asthma to be cautious around airborne irritants. Everyone else, she says, probably shouldn't peg either hopes or worries on aromatherapy.