Can Çiçek S, Demir Ş, Yılmaz D, Açıkgöz A, Yıldız S, Yis ÖM. The effect of aromatherapy on blood pressure and stress responses by inhalation and foot massage in patients with essential hypertension: randomized clinical trial. Holist Nurs Pract. 2022;36(4):209-222.
In hypertensive patients, both inhalation and foot massage with lavender (Lavandula angustifolia) essential oil successfully reduced anxiety, blood pressure, heart rate, and serum cortisol.
A 3-arm, parallel-group, randomized clinical trial
Participants included 69 patients aged ≥18 years who had been diagnosed with essential hypertension for at least 6 months.
Exclusion criteria: currently receiving anxiolytic, hypnotic, or botanical therapy to lower blood pressure; asthma, chronic reactive pulmonary disease, or dialysis treatment; or allergy to lavender.
The study included 3 groups (allocated in a 1:1:1 ratio):
- The inhalation group was exposed to 5 drops of undiluted lavender essential oil (LEO) placed 10 cm away for 5 minutes, between 7 a.m. and 8 a.m. every other day (eg, Monday, Wednesday, and Friday).
- The foot massage group received Swedish massage using 5 drops of LEO on each foot (10 drops total) for 10 minutes on each foot (20 minutes total) between 7 a.m. and 8 a.m., 3 times per week (eg, Monday, Wednesday, and Friday).
- Usual-care patients visited the clinic 3 times, every other day between 7 a.m. and 8 a.m. for measurements. They received no other therapies or interventions.
Study Parameters Assessed
Researchers evaluated 4 parameters: blood pressure, heart rate, serum cortisol, and state anxiety.
- Blood pressure. Researchers assessed blood pressure with a digital sphygmomanometer on first admission after participants had rested for 10 minutes in a quiet room. They again checked blood pressure 10 minutes after inhalation or foot massage.
- Heart rate. After 10 minutes of rest, researchers counted the participants’ apical pulse for 1 minute using a stethoscope.
- Serum cortisol levels. Researchers assessed serum cortisol levels at baseline and within 5 minutes after each administration of lavender essential oil (via inhalation or foot massage), for a total of 4 samples. They did this twice in the control group (at onset and on the 3rd follow-up).
- State anxiety. Researchers evaluated state anxiety at baseline and after the 3rd follow-up.
Subjective measurements were determined using the Spielberger State-Trait Anxiety Inventory (Turkish version). There are 2 scales: one for state anxiety and one for trait anxiety. Each scale has 20 items and a 4-point Likert type. The “state” scale reflects how an individual feels at the moment. The “trait” scale reflects the person’s predisposition to respond anxiously to certain situations.
The researchers aimed to determine whether LEO reduced objective measures (heart rate, blood pressure, serum cortisol) and subjective measures of stress (anxiety state).
At baseline, there were no significant differences among groups in baseline characteristics or for any study parameters.
- Blood pressure changes within each group: Systolic blood pressure (SBP) dropped in the foot massage group over the course of 3 treatments by 7.65 mm Hg, and diastolic blood pressure (DBP) dropped 11.82 mm Hg. In the inhalation group, SBP dropped 11.73 mm Hg, and DPB dropped 13.47 mm Hg. The usual-care group had a 4.39 mm Hg increase in SBP and a 4.6 mm Hg increase in DBP.
- Heart rate: Heart rate in the inhalation group decreased significantly compared with the usual-care group (a 5.08 beats/min decrease in the inhalation group compared with a 3.17 beats/minute increase in the usual-care group).
- Cortisol: Serum cortisol levels decreased over the course of the 3 treatments in the inhalation (3.27 μg/dL) and foot-massage (2.65 μg/dL) groups and increased in the usual-care group (1.25 μg/dL).
- Subjective parameters: State anxiety decreased in the foot-massage group (11.22, P<0.001) and the inhalation group (4.60, P=0.005). In the usual-care group, there was a decrease of 0.18, which was not significant (P=0.909).
The authors disclosed they have no significant relationships with, or financial interest in, any commercial companies pertaining to this study.
Practice Implications and Limitations
The researchers noted some of the challenges in their research design, including a heterogenous group of hypertensive patients divided between 2 hospitals, attending cardiology, neurology, or internal medicine clinics. The patients were prescribed a variety of different antihypertensive drugs, which could have had varying impacts on blood pressure and heart rate variability. They noted the physical and psychological impacts of conducting the research in a hospital setting and acknowledged they could assess only instantaneous changes from the essential oil exposure. They posited that the results might have been quite different if patients had continued the treatment at home, for an extended period.
The researchers did not use gas chromatography and mass spectrometry to test the authenticity of the essential oil used in the study. This crucial step ensures that the essential oil is both unadulterated and authentic, ie, made from a whole-plant source rather than “brokered” (composed of an incomplete combination of isolated constituents prepared by a chemist). The researchers in this study either omitted this procedure or failed to report it.
This study also highlights the challenges in defining a “dose” of an essential oil, particularly when comparing different application methods. When inhaled, essential oils rapidly pass into the bloodstream and cross the blood-brain barrier.1,2
To test dermal absorption, Jager et al massaged a 2% dilution of lavender essential oil into the abdominal region of participants and tested blood levels of linalool and linalyl acetate, 2 of the major constituents of LEO.3 Blood analysis with gas chromatography and mass spectrometry revealed linalool and linalyl acetate present in the blood within 5 minutes of the aromatherapy massage application. The levels peaked at 20 to 30 minutes with a half-life of approximately 60 minutes. Blood levels returned to baseline after approximately 90 minutes.
Aromatherapy is a new enough science that we do not have exact measures to compare a “dose” of an essential oil delivered via inhalation versus dermal application. Factors that influence the effects of an essential oil application include the delivery method, concentration, duration of exposure, and frequency of exposure.
For example, a 2% dilution of an essential oil inhaled for 5 minutes would have a different effect than a 100% dilution of the essential oil inhaled for the same length of time. Similarly, applying the undiluted essential oil on the skin would deliver a different dose than a 2% dilution.
In this study, the inhalation group was exposed to 5 drops of LEO, while the foot massage group was exposed to 10 drops (ie, twice the dose). The treatment time also varied. Researchers exposed the inhalation group to 5 drops of LEO for 5 minutes, from a distance of 10 cm. In contrast, the dermal application group was exposed to 5 drops of LEO massaged directly into each foot for a total of 20 minutes. Massage increases local circulation, which in turn could enhance absorption. In addition, the foot massage lasted 20 minutes, 4 times longer than the inhalation group’s exposure. Dermal application also implies inhalation, as the subjects would be inhaling the essential oil simultaneously along with the dermal application. They would be receiving a “double dose” via 2 delivery methods, during the foot massage.
Inhalation and dermal application may also be used in combination—for example, inhalation during the day and foot massage in the evening before bedtime.
When we consider that the foot massage provided both dermal and inhalation exposure, delivered twice the dose, and lasted 4 times longer than the inhalation-only group, the greater improvement in subjective anxiety in the foot-massage group is not surprising. The foot massage itself, even without LEO, might have reduced stress and anxiety. A more balanced comparison between the 2 application methods might have been a 10-minute foot massage and a 20-minute inhalation exposure. Again, this is conjecture, as we do not currently have accurate dosage comparisons between inhalation and dermal applications of essential oils.
This study did not include asking patients about their scent preferences. To maximize the benefit of the therapy, patients ideally would receive scents they enjoy. Matsunaga et al were the first to connect “odor-evoked biographical memory” with positive effects on both the autonomic nervous system and the immune system.4 Herz furthered this work, demonstrating that positive associations with scent may have beneficial effects, inducing “emotional and physiological responses that can improve human health and wellbeing,” which is a separate consideration from the therapeutic actions of an essential oil.5 Herz’s work suggests that “positive autobiographical memories” in certain subjects may enhance the effects of a scent—in this case, the therapeutic actions of the LEO. Negative associations presumably may undermine the therapeutic actions of an essential oil, though Herz does not explore this in her research.
In the paper currently under review, Can Çiçek et al clearly demonstrate that LEO is an ally for reducing stress via decreasing systolic and diastolic blood pressure, heart rate, and cortisol levels. Other studies have demonstrated similar results.6-8
Can Çiçek et al’s study, however, does not clarify the best application method for delivering the essential oil. In truth, the best application method will likely be determined by the patient’s preferences. Inhalation and dermal application may also be used in combination—for example, inhalation during the day and foot massage before bedtime.
Past research by Najafi et al has demonstrated that inhaling LEO twice a day is more effective than inhaling once a day to decrease anxiety in post–cardiac surgery patients.9,10 In light of this research, “dosing” the essential oil 2 to 4 times a day likely would be more effective in reducing stress and anxiety than a once-daily application.
My usual recommendation for an inhalation “dose” of an essential oil is either holding the essential oil close to the nose and taking 10 deep breaths or breathing normally for 10 to 15 minutes. The essential oil can be delivered on a cotton ball or an inhaler with a cotton wick. The personal inhaler allows patients to “dose” the essential oil in public places (eg, a workplace or a hospital) without exposing other people in their surroundings to the essential oils.
Can Çiçek et al’s research suggests that LEO inhalation and dermal application are safe, effective treatments for relieving stress and anxiety in hypertensive patients. Recommending several applications per day may have greater therapeutic effect than the once-daily exposure used in this study.