The spell of smells

Special to The Times

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 scents can have a direct effect on the body. On the yucky side, for instance, nothing makes me nauseated more quickly than the odor of those “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.

And there is plenty of science behind the sense of smell: In fact, unraveling some of the mysteries of olfactory biology led to a Nobel Prize in 2004.

But there’s little solid science behind many of the claims for aromatherapy -- so little in fact, that the government’s National Center for Complementary and Alternative Medicine does not even discuss aromatherapy on its website.

It is precisely this lack of data that makes aromatherapy so important to study, says Ohio State University health psychologist Janice Kiecolt-Glaser. The federal agency is now funding a study in which Kiecolt-Glaser exposed some people to lavender, a supposed relaxant; others to lemon, supposedly stimulating or uplifting; and the third group to odorless distilled water. (She’s currently analyzing the results.)


Despite the dearth of data, “there have been some pretty wild claims” about the effects of aromatherapy, says Dr. Charles J. Wysocki, a behavioral neuroscientist at the Monell Chemical Senses Center in Philadelphia who has spent more than 30 years studying smell.

Proponents of aromatherapy point to several studies that they claim show the practice works: data suggesting that pleasant odors such as rose, jasmine and lavender may lower blood pressure, and a small study suggesting that lemon oil may reduce the doses needed of antidepressants.

But the benefits are only weakly seen, if at all, in better-designed studies.

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

A 2001 study of 33 patients with post-surgical nausea found that peppermint oil was no better than rubbing alcohol or salt water in bringing relief. A 2002 study of 17 hospice patients found that using a humidifier with plain water was just as effective (and not very) as water with lavender oil in relieving anxiety and pain.

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 last year in the journal Psychosomatic Medicine showed that those exposed to either a pleasant odor (lemon) or an unpleasant one (machine oil) actually had a greater response to experimentally induced pain than those not exposed to an odor.

“It’s very difficult to demonstrate positive effects” from odors, Wysocki says. 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.”

Perhaps that’s because the brain is especially tuned to detect “bad” odors -- such as rotting food -- that could signal danger.

Reactions to odors 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 says.

Expectations also play a huge role in reaction to scents. In one of his own studies, Wysocki and co-workers divided subjects into groups of 30 people and exposed them to an unknown odor. The people who were told they were getting aromatherapy quickly got used to the odor and soon stopped smelling it at all, whereas the group that was told the odor could be dangerous in high concentrations was increasingly bothered by the odor over time.

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 lavender oil massage. Is it the massage? The oil being absorbed into the skin? The scent of the oil? The attention? All of the above?

My take? Enjoy a nice, warm, scented 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.