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March 17, 2008

The OSU Aromatherapy Study-- the real story

Two recent posts (here and here) have documented the publication of a study entitled "Olfactory influences on mood and autonomic, endocrine, and immune function"  and an accompanying press release about it entitled "AROMATHERAPY MAY MAKE YOU FEEL GOOD, BUT IT WON’T MAKE YOU WELL". There have been a number of comments from Aromatherapists on some blogs and mailing lists about the study--mainly based on the press release. Although we are not necessarily defending the study here we feel that the study should be judged on its own merits (or deficiencies) and not on what the OSU Public Relations department has released to the public.

What the study is about

In the introduction the the paper, the authors cite two main references (Price and Price, 1999) and (Hirsch, 2001) with a few others, to define what aromatherapy is, and effectively limit the scope to inhalation aromatherapy, although that is not specifically stated. They cite three mechanisms for how aromatherapy works: Systematic effect theory that "posits that essential oils act like a drug or enzyme", immune function enhancement, and relaxation. They state that "efficacy data are scant, and potential mechanisms of action are controversial." After briefly reviewing some of the literature for lavender, lemon, and placebo (the three oils of choice for the study) they then set forth the exact parameters that they felt defined the study:

To compare and contrast the diverse perspectives about whether and how odors affect health, we examined the autonomic, endocrine, and immune consequences of one purported sedating or relaxant odor, lavender, one activating or stimulant odor, lemon, and distilled water as a no-odor control during both resting and “challenge” or stress conditions in a mixed or between-within repeated measures design; each subject served as his or her own control during three separate 6 h[our] visits. Depending on their random assignment, participants were either given no information about what odors they would be smelling or what to expect (the “blind” group), or they were told what odors they would smell and what changes to expect from the relaxant, stimulant, or no odor exposures (the “primed” group).

Our protocol for each session included a cold pressor, a laboratory stressor that elevates stress-related hormones, heart rate, and blood pressure (Blandini et al., 1995; Hirsch and Liebert, 1998). Both before and after the cold pressor we performed tape stripping, a common dermatological paradigm for studying restoration of the skin barrier, a process mediated by both endocrine and immune systems (Choi et al., 2005). Our design thus provided a way to examine the ability of lemon and lavender odors to modulate stress and pain responses to the cold pressor, as well as wound healing via the speed of skin barrier repair.

In summary, they evaluated two essential oils and a water placebo via inhalation and measured some physiological parameters to determine if there were actual effects. The final paragraph of their introduction summarizes the predictions of results that they expected to obtain from the study and defines the parameters to be measured:

Specific predictions can be derived from the various theories posited to explain the effects of essential oils. For example, if the systemic effect theory is correct, even relatively short-term exposure to lavender would be expected to produce larger declines in the production of cortisol and catecholamines, faster skin barrier repair, lower pain ratings in response to the cold pressor, and smaller stress-related immunological changes compared to lemon and the no-odor control; short-term exposure to lemon oil should produce greater transient increases in positive affect, heart rate, blood pressure, and catecholamines than either lavender oil or the no-odor control. If expectancies determine the pattern of responses (Jellinek, 1997), then the primed group's mood and physiological responses to lemon and lavender odors would be greater than the blind group; similarly, those with positive expectancies about aromatherapy in advance of participation would be expected to show greater changes. By assessing olfactory influences on mood and autonomic, endocrine, and immune function, our design allowed us to contrast these diverse conceptual perspectives, clarify mechanisms, and assess possible clinical efficacy.

I'm probably push the boundaries of fair use in my quoting, but I want to be fair to the authors and it's really hard to summarize this stuff very well.  See what happened when they tried at the OSU Public Relations department, or even in the summary to the paper.


I've reviewed the methodology and won't go into detail here, other than to summarize.  They had 56 participants in the study; they excluded people who might have adversely affected the study (such as those with no or a reduced sense of smell); they attempted to control any variations in methodology by standardizing the application of the oils and the measurements. One thing that I initially questioned was that they froze the essential oils (at -80C) and thawed only enough to use at the time of a session, but they did perform MSGC's on the oils at the beginning and periodically throughout the study to verify that there were no changes.  Dr. Robert Tisserand assured us that freezing should not be a problem causing variability. They obtained their essential oils from a Chemical Supplier, but they provided no specific lot or country of origin data. The vendor has online data available for other lavenders (a 40/42 that came from Russia, for example), but not for this one. The vendor has two lemon oils, but neither has the correctly spelled botanical name and it's not clear which one was used. There is no evidence in the paper that the oils used were appropriately of aromatherapy quality.

The paper describes in detail exactly how they measured each of the parameters; how the experimenters were blinded so they couldn't tell which odor was being used, and how the data were gathered. I'm not going to go into detail here; the methods appear to be adequate to the non-expert.  They've stated their methods of statistical analysis in general terms.  Since the study was peer-reviewed, we should probably assume that they got the data analysis right.

The method of application of the odors has been questioned. Since they applied the odor to the participants for a period of several hours, and during that time the participants were being tested, they needed a standardized way to apply it. So they applied 100 microLiter of the EO to a cotton ball and taped it between the nose and the upper lip on top of a piece of surgical tape barrier to avoid absorption through the skin. What wasn't made clear in the press release was that they replaced the cotton 4 times [at irregular intervals] during the study period to maintain odor strength and they removed the cotton ball for a lunch break, then applied a new cotton ball to complete the testing.

Another potential issue was the mention in the paper of placement of a "heparin well" in the arm of each participant at the beginning of the session and its removal at the end. Since heparin is a chemical anticoagulant (that has been in the news lately because of bad material imported from China), we were concerned that its presence might bias the results.  However, a Google search revealed that the well is merely an IV tube that is placed to allow easy access for taking blood samples during the study.  Apparently it's a common practice during research at OSU. There was no heparin introduced into the body during the testing.


The results listed in the study summary were summarized so as to be difficult to understand to the lay reader.   The authors presented the results of each of the tests in either descriptive or graphical form. The results are subject to interpretation and that is done in part 4 of the paper, entitled Discussion. That will be covered in a future post.

Summary of Problems observed by me:
  1. The source and characteristics of the Essential Oils used were not adequately stated and tracked. The authors took care to maintain the oil quality during the study, but there is no way to tell whether the oils were any good to start with. MSGC data should have been included in the paper as well. 
  2. The odor strength was not uniformly and consistently maintained because the interval between changes was not standardized, and because of the lunch break. Even if it had been, it can be questioned as to whether it should have, since intermittent application is the usual mode in aromatherapy. 
  3. The practice of continuous application of the odorant materials during the entire test is not in accord with my understanding of normal aromatherapy practice, although the paper seems confused on the issue, citing one intermittent study (Goel et al., 2005) and one with "short term inhalation," whatever that means. 
  4. No trained aromatherapist was apparently consulted about the study. It might also have been useful to have the opinion of a trained aromatherapist as to the quality of the oils used and their suitability for aromatherapy.

(only these mentioned in this post are included here--the full paper has 41 references listed).

Blandini et al., 1995 F. Blandini, E. Martignoni, E. Sances, G. Bono and G. Nappi, Combined response of plasma and platelet catecholamines to different types of short-term stress, Life Sci. 56 (1995), pp. 1113–1120. Abstract | Full Text + Links | PDF (595 K) | View Record in Scopus | Cited By in Scopus (11) 

Choi et al., 2005 E.-H. Choi, B.E. Brown, D. Crumrine, S. Chang, M.-Q. Man, P.M. Elias and K.R. Feingold, Mechanisms by which psychologic stress alters cutaneous permeability barrier homeostasis and stratum corneum integrity, J. Invest. Dermatol. 124 (2005), pp. 587–595. View Record in Scopus | Cited By in Scopus (25) 

Hirsch, 2001 A.R. Hirsch, Aromatherapy: art, science, or myth?. In: M.I. Weintraub, Editor, Alternative and Complementary Treatment in Neurologic Illness, Churchill Livingstone, Philadelphia, PA (2001), pp. 128–150. 

Hirsch and Liebert, 1998 M.S. Hirsch and R.M. Liebert, The physical and psychological experience of pain: the effects of labeling and cold pressor temperature on three pain measures in college women, Pain 77 (1998), pp. 41–48. Abstract | Full Text + Links | PDF (60 K) | View Record in Scopus | Cited By in Scopus (13) 

Jellinek, 1997 J.S. Jellinek, Psychodynamic odor effects and their mechanisms, Cosmet. Toilet. 112 (1997), pp. 61–71. 

Price and Price, 1999 S. Price and L. Price, Aromatherapy for Health Professionals, Churchill Livingstone, Edinburgh (1999). Here in Google Books

Tisserand, 2008 Robert Tisserand, Personal Communication to blog author.

Posted by Rob on March 17, 2008 in Aromatherapy, Essential Oils/Plant Extractions, OSU Aromatherapy Study, Research | Permalink


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I have a question:

The oils were frozen, then thawed. Was there any indication as to what temperatures the oils were at when testing was started? Any idea what they were at other points during the studies?

Or is it your opinion that the temperatures they were at wouldn't matter?

Posted by: Serra | Mar 18, 2008 1:02:23 PM

Nice post.

I agree with you that the quality of the oils is determine the result. Applying the essential oils topically instead of simply sniffing might also have produced different effects.

Posted by: www.aromatherapy-at-home.com | Mar 19, 2008 6:40:08 AM

They didn't say what the temperature was when they started testing, but presumably it was at room temperature. They took samples to do MSGC's after the oils were thawed and before they were used.
Since the oils were placed on the cotton pad, they would have been at room temperature when initially inhaled, and gradually risen in temperature as exhaled breath passed over them.
However, the changes in temperature during the testing were probably trivial and wouldn't have had much effect on the tests. I don't know whether anyone has ever studied the microclimate of odor diffusion--it might make an interesting study. I guess I'll have to look that up.

Posted by: Rob | Mar 20, 2008 10:11:50 PM

The article is very nice i liked it and i also have some stuff to share with you all on Aromatherapy at http://www.mountainessence.com/

Posted by: George Kakaris | May 13, 2008 3:53:47 AM

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