When it comes to aromatherapy, it could really be possible to have too much of a good thing.
Taiwanese researchers found that the positive effects of aromatherapy -- where breathing in the aromas from essential oils can have calming, blood pressure-lowering effects -- can actually turn into negative ones if you engage in the therapy for longer than an hour.
"Our results suggest that exposure to essential oil for one hour would be effective in reducing heart rate and blood pressure," study researcher Dr. Kai-Jen Chuang, of the Taipei Medical University in Taiwan, said in a statement. "However, the most interesting finding of our study is that exposure to essential oil for over an hour was associated with elevated blood pressure and heart rate."
The small new study, published in the European Journal of Preventive Cardiology, included 100 young, healthy men and women who work in spas. About once a week for three weeks, the study participants underwent two-hour aromatherapy sessions of pure bergamot essential oil via an ultrasonic ioniser, all while having their blood pressure and resting heart rate monitored.
The study participants' blood pressure and resting heart rate decreased with 15 to 60 minutes of the aromatherapy, but then their resting heart rate and blood pressure began to increase with 75 minutes to 120 minutes of the therapy.
"Prolonged exposure for longer than one hour to essential oils may be harmful to cardiovascular health among spa workers," researchers wrote in the study.
However, Pamela Dalton, Ph.D., who is a research scientist at the Monell Chemical Senses Center, told WebMD that it's possible the negative effect of "too much" aromatherapy may not lie in the actual aromatherapy.
"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 told WebMD.