Professor Novella discusses the rise of essential oil use. He states, “Aromatherapy with essential oils is pseudoscience, backed only with low quality studies guaranteed to show a placebo effect. Their growing popularity warns that better science education is needed.”
This article originally premiered on Science Based Medicine.
Tri-State Ambulance operating in the La Crosse, Wisconsin area has started using essential oils to treat minor pain. This is now a new front on the struggle against the infiltration of pseudoscience into medicine. Similar to acupuncture, it represents a fundamental failure of medical education.
The goal of any science-based system, which medicine should be, is to have clear and valid procedures for reliably answering basic questions – in the case of medicine, questions about safety, efficacy, and fundamental issues of biology and mechanism of action. In short we need to be able to adequately address the question – is this phenomenon real, and what exactly is it?
Promoters of snake oil (whether naïve or intentional) fail at this basic task. They have also discovered the weak points in the medical system where they can infiltrate. This is where the failure of medical education comes in, because it should be obvious to any trained health professional that these interventions are not scientific. We should be holding the line against pseudoscience, and then educating the public about what is legitimate and what isn’t. Instead, far too many health care providers become deceived themselves and then promote pseudoscience. Then the entire system starts to crumble as we see a proliferation of specialists, journals, products, and services in the mainstream based on bad science.
What Tri-State Ambulance Is Doing
Dr. Chris Eberlein, medical director for Tri-State, said he noticed paramedics were often giving small doses of narcotics like fentanyl to patients who ended up not needing a prescription for pain medication.
“We started reviewing ‘Why are they giving narcotics?’ and really it came down to the fact that they didn’t have many other things they could do in the ambulance ride,” Eberlein said.
That is a real issue, the overuse of narcotics for minor acute pain. Using a fake treatment, however, is not the answer. The last line of the report also states:
Tri-State paramedics will also have access to liquid Tylenol as another alternative to opioids.
Why not skip the snake oil and go right to the Tylenol? If you need something stronger but don’t want to use a narcotic, there is also tramadol. There is a range of options, but now it seems like the allure of doing something novel and “natural” is distracting from real medicine.
Eberlein also says that patients feel better because of the pleasant odor of the oils, and that ambulances otherwise smell very sterile. Allow me to introduce you to the concept of the air freshener.
Reading the comments to the article we find the now typical polarization from skeptics to true believers. The skeptics point out (correctly in my opinion) that pseudoscience has no place in modern medicine. The believers reply with the usual range of responses – keep an open mind, medicine is poison, and hey, there is lots of evidence if you just look.
OK – let’s take a look at the evidence.
Evidence Or Essential Oils
Before I review the published evidence concerning the efficacy of essential oils, let me review what should be a reasonable standard of evidence. If we sincerely want to know if any particular essential oil is effective when applied in a specific way for a specific condition, then we need to conduct carefully-designed clinical trials.
The core of any well-designed scientific experiment is that it adequately controls for all possible variables and confounding factors. In medical trials we want to isolate the treatment itself from all other possible effects, and then objectively measure an appropriate outcome. So if we want to know if Rosa damascena Mill. is effective for reducing pain, we need to compare it to adequate controls in a double-blind study. Controls should include a group receiving only the carrier oil, another with a similarly pleasant odor but not Rosa damascena Mill., and perhaps a control group with no intervention.
Pain is challenging to measure in an objective way, so most studies resort to subjective patient report. That is why the studies have to be properly blinded and adequate controls are essential. You can use pseudo-objective measures, like the need for additional pain medication, functional ratings, and other markers of their health outcome as appropriate. And of course, studies need to be large enough and carried out for long enough to get adequate data, and executed to prevent p-hacking.
This article is part of our Professor’s Perspective series—a place for experts to share their views and opinions on current events.
Very similar to the acupuncture literature, most studies are designed (in effect, if not intent) to show a positive result. They rely heavily on unblinded comparisons (to a no-treatment or no-odor group, for example) and subjective outcomes. Such studies are almost guaranteed to be positive, which means they actually tell us absolutely nothing.
There are also many studies looking at the properties of specific essential oils in vitro. These are interesting basic science studies, which basically show that the oils are drugs (because they are) with pharmacological properties. None of these studies, however, can be used as a basis for clinical claims. We know from a century of experience that such basic science studies rarely translate to a clinical application.
One main reason is bioavailability. When you directly expose cells in a culture to a compound, what happens in that setting may say nothing about what happens when the same substance is taken by a living organism. Little or none of the compound may get absorbed or find its way to the target tissue. In the case of essential oils, they are often delivered by aromatherapy – smelling. Who knows what the bioavailability is of each of these compounds by this particular route of administration?
All the individual studies I found had serious methodological flaws. Few are double-blind, some are single-blind, and most are unblinded. The better designed studies tend to have mixed results, and reek of p-hacking.
There are several systematic reviews of specific essential oils for various types of pain. They also show the same kind of results as acupuncture reviews. The reviews are negative, meaning that no specific treatment has crossed the threshold of evidence where we can honestly say that it has been shown to work. Rather, all the reviews report that the evidence is not sufficient, and the precise spin depends on the reviewers and the journal. Cochrane reviews give the typical, “More and better quality research is needed.” Alternative medicine journals call the treatments, “promising” or similar.
Here are some examples – starting with a study of rose oil for pregnancy related low back pain:
A randomized controlled clinical trial was conducted on 120 women with pregnancy-related low back pain. Patients were allocated to 3 parallel groups to receive topical rose oil (in the carrier of almond oil), placebo (carrier oil), or no intervention. All groups were followed for 4 weeks. All participants were evaluated by Visual Analog Scale and the Roland-Morris Disability Questionnaires to assess the pain intensity and its impact on daily activities before and after the intervention. Significant decrease in pain intensity compared to carrier oil or no intervention was observed. The rose oil also improves the functional ability of these patients in contrast with no intervention, while its effect on function is not significant compared to carrier oil.
Notice that the study is not double-blinded. Further, we see a difference in the subjective measure, but in the more objective measure (functional ability) we only see a difference with the no-intervention group, and not with the carrier oil group. This is the exact pattern of results we would expect from a placebo-only intervention. Positive results are dependent upon subjective outcomes and unblinded comparisons, with interventions that should provoke more of a placebo effect showing more of an effect. The best comparison, between rose oil and carrier oil in the functional ability assessment, was negative.
Here is another study of lavender oil and osteoarthritis of the knee:
In this single-blinded, randomized clinical trial, 90 patients with osteoarthritis of the knee who referred to the outpatient rheumatology clinics affiliated with Birjand University of Medical Sciences were selected through convenience sampling method. They were randomly assigned to three groups: intervention (aromatherapy massage with lavender essential oil), placebo (massage with almond oil) and control (without massage). The patients were evaluated at baseline, immediately after the intervention, 1 week, and 4 weeks after the intervention in terms of pain via visual analogue scale. The data were analyzed in SPSS (version 16) using the repeated measure ANOVA, one-way ANOVA, and chi-squared test.
Pain severity of the patients in the intervention group was significantly different immediately and 1 week after the intervention compared with their initial status (p < 0.001) and that of the control group (p < 0.001 and p = 0.009 respectively). However, at the third phase of follow-up (i.e., 4 weeks after the intervention), there was no significant difference between the groups according to the visual analogue scale (p = 0.67).
Subjects were not blinded and the outcome was subjective, so right there the results are mostly useless. Further, we see the same pattern as above. When compared to no intervention at all, there is a placebo effect (surprise). When comparing lavender oil to almond oil, there is no difference. They didn’t even bother stating this explicitly in the abstract.
This study also shows additional features of a typical placebo intervention. First, the results were short-lived, present at 1 week but not 4 weeks. Second, the researchers mixed variable by including massage. So essentially we can conclude from this study that massage has short term subjective effects on knee pain, but essential oils add nothing to the efficacy.
One more to show an additional feature, Rosa damascena Mill. for migraine headaches. This was one of the rare double-blind studies, but was small, with only 40 subjects. Here are the results:
Mean pain intensity of the patients’ migraine headache in the different time-points after R. damascena oil or placebo use, was not significantly different. Additionally, regarding mean scores of N/V, photophobia, and phonophobia severity of the patients, no significant differences between the two groups were observed. Finally, applying syndrome differentiation model, the mean score of migraine headache pain intensity turned out to be significantly lower in patients with “hot” type migraine syndrome at in 30, 45, 60, 90, and 120min after R. damascena oil application compared to “cold” types (P values: 0.001, 0.001, <0.001, <0.001, and 0.02; respectively).
See what’s happening here? First, we again see an inverse relationship between quality of study design and outcome. In this double-blind study, there was no difference at all between the treatment group and the placebo – so this is a negative study. But wait, they did a subgroup analysis and found a difference for “hot” type migraines vs “cold” type. What are hot vs cold migraines? That’s a new one on me, and nothing comes up when I search on it (except for this one study). In short – the whole thing has the strong aroma of p-hacking.
What about the systematic reviews? Here’s one of Rosa damascena Mill in pain relief:
There are promising evidences for the effectiveness and safety of Rosa damascena Mill in pain relief, but confirmatory studies with standardized products is suggested.
This was published in the journal Complementary Medicine Therapy. So they use the buzzwords “promising” and “confirmatory studies suggested” which is code for – the evidence is lacking.
Here is a Cochrane review of aromatherapy for symptoms of cancer:
There was a lack of evidence on the clinical effectiveness of massage for symptom relief in people with cancer. Most studies were too small to be reliable and key outcomes were not reported. Any further studies of aromatherapy and massage will need to address these concerns.
The Cochrane authors are more blunt – the evidence is crap.
This is now the standard of science for “alternative” treatments. Do a lot of basic studies showing that “stuff happens” in the petri dish. Then do worthless clinical trials with inadequate designs guaranteed to show a placebo effect, and use them to declare your treatment “evidence-based.” This will help your true-believers (and marketing team) who can point to all this evidence, and then call skeptics “closed-minded.”
Doctors should know enough science to see through all this, and many do, but unfortunately many cannot. They combine terrible science with personal anecdotes and then use their professional status to lend credence to pseudoscience, and become the gateway for the infiltration of this pseudoscience into our profession.
For more with Professor Novella, check out “Medical Myths, Lies, and Half-Truths” on The Great Courses Plus!