Sniffing out the truth on dueling aromatherapy studies

The following is a guest post by Earle Holland, who, for almost 35 years, was the senior science and medical communications officer at Ohio State University. He’s been a member of our editorial team since January.

Lavender herb and essential oilIt started as a Facebook post from a friend of a friend, a comment excitedly anticipating the arrival of a box of essential oils, the key ingredients of so-called aromatherapy.  Some supporters of alternative medicine tout the benefits of aromatherapy, that it does more than simply improve moods and reduce stress, but can actually improve immunity and reduce pain.

Even the Mayo Clinic, widely respected throughout the medical community, explains on its website that studies of the use of lavender oil “may help make needle sticks less painful” and “reduce pain for children undergoing tonsillectomy.”

And as the Facebook discussion progressed, the comments became more and more effusively supportive, one respondent gleefully said that she had bought the “Family Physician Kit,” suggesting an actual medicinal effect.

In truth, it was just so much light-hearted banter among friends, nothing serious at all.  But as those of us who’ve spent lifetimes in the battles between science and pseudo-science well know, such conversations can often lead to more fallacy than fact among the public.

Seven years ago, I had reported on research by a team of world-class scientists looking at the claims of aromatherapy proponents.  These experts had spent more than three decades finding connections between psychological stress and problems with immunity, wound-healing, vaccine effectiveness, cancer outcomes and a host of other concerns.  They had found dozens of situations where stress had increased the production of hormones and other biochemical markers that had an actual physiological effect on health outcomes.

They had turned their attention to testing two popular oils – lemon and lavender – to see if either caused changes that they could measure, differences which normally connote a change in human health.  They used a standard test for both pain and for wound-healing, all the while taking blood samples throughout the tests.  They looked for changes in stress hormones like cortisol, norepinephrine and other catecholamines, as well as levels of cytokines like interleukin-6 and interleukin-10, both known to vary with immune changes.

There were 56 healthy volunteers in the tests, some whom had favorable views about aromatherapy and some who had no opinion, and all completed several standard psychological tests to gauge stress levels during the research sessions.  At the time, I wrote:

“While one of two popular aromas touted by alternative medicine practitioners – lemon – did appear to enhance moods positively among study subjects, the other – lavender – had no effect on reported mood, based on three psychological tests.

“Neither lemon nor lavender showed any enhancement of the subjects’ immune status, nor did the compounds mitigate either pain or stress, based on a host of biochemical markers.

“In some cases, even distilled water showed a more positive effect than lavender.”

The study was published in the journal Psychneuroendocrinology and had been supported by the National Institutes of Health.  The aromatherapy industry, understandably, was not pleased.

I offered a link to that study to the participants in that Facebook discussion.

Soon after, one of the posters offered an opposing link, one pointing to a study of the use of such oils to reduce stress in the Vanderbilt University Medical Center’s Emergency Department. [Editor’s note: we could find no link to a published paper on the study, so we are linking to the report from the Facebook discussion, which in turn links to this magazine article about the study.]   It looked at the use of these oils to lower perceived stress among the staff working in that ER.  The two nurses conducting the study had asked staff to complete survey instruments reporting their stress levels before and after the use of the oils.  Their findings seemed to clearly support the value of the oils in reducing stress:

“Before the use of essential oils, 41 percent of staff members surveyed felt work-related stress very often.  After the use of essential oils, only 3 percent felt work related stress very often.”

The surveys reported similar improvements in staff’s feelings of being overwhelmed, in their energy levels, and in their perceived ability to handle stress.

So this was a case of competing studies with opposite findings, right?

Not hardly!

And that’s the point in bringing this whole issue up.  In no way were the two studies comparable.  The first looked for objectively measurable biochemical markers known to change when stress is involved.  Many, many previous studies covering a host of conditions had shown their effectiveness in measuring the impact of stress, as well as the health outcomes from that stress.

The Vanderbilt study was a self-reporting survey, with individuals stating their subjective perceptions of their status.  There was no control group to compare with.  There was no mention of the ER staff being blinded to the use of the oils.  And there were no biochemical markers taken which could actually show a change in stress responses, nothing to rule out that the observed changes were anything more than a placebo effect.

And that’s the main problem with situations like this.  The public is confronted with two pieces of research, studies which may be radically different in their design and ability to produce high-quality evidence.  But most people are ill-equipped to gauge the differences.  All too many are unwilling to investigate reports beyond a simplistic understanding.

It’s just much easier to assume that all studies are equal.

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Comments (5)

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September 15, 2015 at 5:24 pm

Yay, Earle!!

Eric Fishman, MD

September 15, 2015 at 10:09 pm

Interesting perspective.
What do you say about the dozens of studies at that show clear evidence, in humans and rats, that terpenes, the purported active agents in many aromatherapy treatments, provide clear physiological benefits when administered in lab settings? (References available upon request).


September 16, 2015 at 9:03 am

Sir. I have read these over the years. The article you tout here as being the good research is not.
A fragrance is not an essential oil and therefore not a valid methodology tool and neither is a cold pressor ice bath on an extremity. I thought this psychology group should know that smelling anything does not abolish the pain of a prolonged ice water bath.
James Geiger MD

Earle Holland

September 16, 2015 at 1:32 pm

Eric: I was fairly specific in referencing a study focused on two popular scents used in aromatherapy which have been touted as having a positive physiological effect on humans. The study was funded in part by the National Center for Complementary and Alternative Medicine at the National Institutes of Health. The following excerpt from the conclusion to their paper may be helpful:
“Many complementary/alternative therapies have not been subjected to well-controlled tests. The data from this randomized controlled trial are important because they directly address both potential mechanisms and clinical efficacy. We chose lemon and lavender because they are widely used purported stimulant and relaxant odors, and health benefits have been repeatedly ascribed to them, particularly lavender. Our sample included regular aromatherapy users as well as skeptics, so we also investigated the possibility that ‘‘true believers’’ might show greater benefits. We found clear and consistent evidence that lemon oil inhalation enhances positive mood and also boosts norepinephrine release (in line with its activating properties), but no other obvious physiological or health-related benefits from either lemon or lavender; indeed, the finding that both odors appeared to depress DTH (delayed hypersensitivity to Candida) responses relative to water suggests that the immunomodulatory effects of these odors were negative, at least for this aspect of the immune response.”
James: Concerning your point that “a fragrance is not an essential oil,” this from the methodology portion of this paper may help:
“A yellow-tinted cotton ball containing 100 microliters of the essential oil or distilled water was taped between the nose and upper lip on top of a piece of surgical tape; use of the barrier tape avoided percutaneous absorption. This method provided continuous and uniform exposure across subjects that would not have been possible with ambient room inhalation, and helped maintain experimenter blindness. Both oils were initially characterized using mass spectrometry and gas chromatography by the vendor and confirmed by the Ohio State Chemical Instrumentation Center every 8–10 months to test variability in thawed aliquots, focusing on the key active components of each oil.”
As to your contention that cold pressor ice bath is “not a valid methodology (sic) tool,” this, also excerpted, may help:
“Widely used in behavioral and psychophysiological research, the cold pressor provided a way to assess the impact of odor on both acute pain and physiological recovery after a stressor (Blandini et al., 1995; Hirsch and Liebert, 1998). After sitting quietly for a 15-min adaptation period, participants immersed their right foot up to their ankle for 1 minute in warm (37 degree C) water, and then immediately immersed their foot in a pan of 4 degree C water for 1 minute (Hirsch and Liebert, 1998). Participants rated pain intensity on a 1–10 scale at the end of the cold pressor.”
But you both seem to have missed the main point — that so-called “studies” are not all of equal merit, that a self-reported survey is not equivalent to a blinded, randomized, controlled trial that provides biochemical information about a person’s physiological response to inhaled essential oils. That should be fairly obvious.__EH

    Eric Fishman, MD

    September 26, 2015 at 9:03 pm

    Point well taken. I have often stated that among the reasons for aromatherapy remaining as a ‘pseudo-science’ is the extreme difficulty in providing the gold-standard double blind study. I find it difficult to envision a study in which two people are asked to go to sleep (for instance) either with or without the fragrance of lavender on their pillow – and have the subjects not know whether or not they are smelling lavender.

    Tangentially related, I’ve recently written about a theory regarding why aromatherapy should work in the first place. I agree in advance, that this is not specifically addressing your concern about the validity of various studies, but it does provide an interesting perspective on why aromatherapy may provide any benefits. I’d be interested in hearing your opinion on the theory.