Some research questions aromatherapy benefits

medical matters

December 29, 2006|By Judy Foreman

Aromatherapy -- the use of plant oils to improve well-being -- sounds lovely, doesn't it? How wonderful if a whiff of lavender could make you feel drowsy, or a little dab of rosemary oil could relieve muscle pain.

There's certainly a plausible biological basis for the idea that smells can have direct effects on the body.

On the yucky side, for instance, nothing makes me nauseous faster than the odor of those pine tree-shaped air fresheners that taxi drivers hang in their cabs. On the positive side, there's nothing like the scent of a fresh Christmas tree to evoke warm memories of childhood. Or the smell of cookies baking in the oven to help sell a house.

In fact, unraveling the science of smell led to a Nobel Prize two years ago for Richard Axel of Columbia University and Linda B. Buck of the Fred Hutchinson Cancer Research Center in Seattle.

But there's little solid science behind many of the claims for aromatherapy, which usually means soothing the body through smells, but also refers to rubbing plant oils on the skin.

"There have been some pretty wild claims," said Dr. Charles J. Wysocki, a behavioral neuroscientist at the industry-sponsored Monell Chemical Senses Center in Philadelphia who has spent more than 30 years studying smell.

It is precisely this lack of data that makes aromatherapy so important to study, said Ohio State University health psychologist Janice Kiecolt-Glaser. She is analyzing results from a government-funded study in which she exposed one group to lavender, "which is supposed to be a relaxant," she said, and another to lemon, "which is supposed to be stimulating or uplifting." She exposed a third group to distilled water, which has no smell.

There is so little science supporting aromatherapy that the federal government's National Center for Complementary and Alternative Medicine doesn't even discuss it on its Web site, although the agency is funding one study: Kiecolt-Glaser's.

Proponents of aromatherapy refer to several studies that purport to show that it works. Some data do suggest that pleasant odors such as rose, jasmine and lavender may lower blood pressure, and a small study suggests that lemon oil may reduce the doses of antidepressants that patients require.

But the more rigorous the study, the less benefit it shows.

A 2001 study of 33 patients with post-surgical nausea found that oil of peppermint was no better than rubbing alcohol or salt water in relieving post-surgical nausea.

A 2002 study of 17 hospice patients found that using a humidifier with plain old water to relieve anxiety and pain was just as effective (and not very effective, at that) as using water with lavender oil.

A randomized, double-blind study in 2000 of 66 women who were awaiting abortions found that aromatherapy with essential oils (vetivert, bergamot and geranium) was no more effective than a placebo smell (hair conditioner) at relieving anxiety.

A 2003 randomized study of 313 cancer patients undergoing radiation similarly concluded that aromatherapy was psychologically "not beneficial."

Worse yet, a study of 60 healthy men and women, published this year in Psychosomatic Medicine, showed that those exposed to either a pleasant odor (lemon) or an unpleasant odor (machine oil) actually had a greater response to experimentally induced pain than those exposed to no odor at all.

"It's very difficult to demonstrate positive effects" from odors, Wysocki said. By contrast, "it's very easy to demonstrate mood swings in the negative direction. If you expose people to nasty-smelling odors, they will get upset. If you expose them to vomit, some people will actually get sick and vomit," she said.

Perhaps that's because the brain is hard-wired to detect "bad" smells -- odors such as the smell of rotting food, which can signal danger.

Reactions to smells are also highly conditioned. "A child who experiences the smell of roses for the first time on a summertime walk in the garden with his mother will have different memories of the smell of roses than a child who first experiences the smell of roses at his mother's funeral," Wysocki said.

Expectations also play a major role in reaction to smells. In one of his studies, Wysocki's researchers divided subjects into groups of 30 people and exposed them to an unknown smell.

The people who were told they were getting aromatherapy quickly got used to the smell, and soon stopped smelling it at all, while the group that was told the smell could be dangerous in high concentrations was increasingly bothered by the odor as time went on, he said.

Precisely because people expect a benefit from aromatherapy, it may help them feel better, said Cherie Perez, a research nurse supervisor at the University of Texas M.D. Anderson Cancer Center in Houston.

But it's tough to pin down what's going on when someone feels better after a massage with lavender oil, she said. Is it the massage? The oil being absorbed into the skin? The smell of the oil? The attention of the masseuse? All of the above?

My take on this? Enjoy a nice, warm bath if you want to relax. But don't count on the expensive bath oil to help anyone but the company that sold it to you.

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