Authors

  1. Starkweather, Angela PhD, ACNP-BC, FAAN

Article Content

Learning Objectives/Outcomes:After participating in the CME/CNE activity, the provider should be better able to:

  

1. Define aromatherapy and how it may be used as a complementary therapy.

 

2. Differentiate the 4 potential mechanisms by which aromatherapy may influence health and well-being.

 

3. Analyze the evidence on the effectiveness of aromatherapy for reducing pain.

 

Aromatherapy is the use of concentrated essential oils, which are volatile liquids extracted by steam distillation or mechanical expression from flowers, herbs, or trees, to improve health and well-being. Essential oils have been a part of the healing practices of most ancient cultures and were used to treat ailments, such as fever, cough, headaches, psychiatric manifestations, and infection, and integrated into spiritual practices and cultural rituals.1

 

There are many essential oils available for aromatherapy, such as bergamot, cedarwood, Roman chamomile, geranium, ginger, jasmine, lavender, lemon, and tea tree. Each type of essential oil has a unique chemical composition that determines its smell, how it is absorbed, and how it affects the body.2 Essential oils can be inhaled, applied topically, or ingested. However, the most common use is for inhalation.1 Most essential oils have been approved as ingredients in food and fragrances and are labeled by the FDA as "generally recognized as safe" (GRAS). However, aromatherapy products do not need FDA approval unless there is a claim for treatment of specific diseases.3

 

Aromatherapy can be used via inhalation, topical application with or without massage, or in baths. As the essence oils are inhaled through the nasal mucosa, the molecules diffuse to receptors on olfactory sensory neurons, which send messages to the brain, where the smell is interpreted. In the limbic system, the emotional center of the brain, aromas that are familiar can evoke memories and emotions associated with the smell. Aromatic molecules carried to the lungs can enter the bloodstream and travel to other parts of the body. However, the pharmacologic properties of inhaled essence oils have not been verified in humans and many questions remain regarding the proposed pharmacologic effects.4

 

Topical application of essential oils is carried out by diluting the essential oil with a carrier oil (such as sweet almond oil or olive oil). Some of the aromatic oils applied topically have antibacterial, anti-inflammatory, and analgesic effects.3 Allergic reactions may occur when essential oils are used and a skin patch test can be performed to test for allergies, especially in patients who have multiple chemical sensitivities, seasonal allergies, or a history of topical allergic reactions.

 

Another approach for topical application is to start with a low dilution at 1% or less, with gradual increases of 0.5% if there are no signs of an allergic reaction. In infants up to the age of 6 months, the recommended dilution is 1 drop of essential oil in 20 mL of carrier solution, whereas a 0.5% dilution should be used for older children, elderly, and expectant mothers.5 To create a 1% dilution, it is generally advised to use 6 drops of essential oil per ounce (29.6 mL) of carrier oil, whereas a 5% dilution is created with 30 drops to 1 oz of carrier oil. A maximum concentration of 5% is generally considered safe for adults.

 

Although the physiologic/pharmacologic mechanisms by which essential oils may influence health and well-being remain unresolved, other mechanisms have been suggested, including hedonic (pleasantness), psychological, and contextual/associative pathways.6 At this time, the contribution of each mechanism on health and well-being is uncertain, and due to the contextual factors involved, further research using strict methodologic approaches with both subjective and objective measures will be required (Figure 1).

  
Figure 1 - Click to enlarge in new windowFigure 1. Proposed mechanisms of aromatherapy. Physiologic/pharmacologic, hedonic, psychological, and contextual/associative mechanisms of aromatherapy have been proposed to influence health and well-being; however, the relative contribution of each has not been defined.

For example, the active constituents of lavender oil are linalool and linalyl acetate.7 Although pharmacokinetic data on these metabolites have been described in animals, inhalation and topical application of lavender oil in humans do not reach discernable concentration in the bloodstream to mimic these effects.4 Therefore, it seems unlikely that animal studies are comparable to the pharmacokinetics of aromatherapy in humans. However, hedonic qualities of the aroma can produce changes in mood, whereas psychological mechanisms involving expectancy about the odor qualities and its effect on health can also contribute to perceived well-being.8 The contextual/associative mechanism refers to the individual's memory of the odor and associations with particular stimuli within the current status and conditions of the individual.

 

There is a difference between complementary therapy and alternative therapy. It is important to understand this distinction, and the concept of integrative care. Regardless of whether aromatherapy produces a physiologic/pharmacologic mechanism, the hedonic, psychological, and contextual/associative mechanisms may facilitate pain relief when aromatherapy is used as a complementary therapy-that is, an intervention that is used along with standard medical treatment. In contrast, alternative therapies are used instead of standard medical management (Figure 2). From an ethical standpoint, aromatherapy should not be used as an alternative therapy in the treatment of pain because there is no evidence that aromatherapy alone is comparable to standard medical treatment of pain. Integrative care uses a wide range of approaches, including standard medical care and evidence-based complementary and alternative therapies, to treat the patient's mind, body, and spirit.9

  
Figure 2 - Click to enlarge in new windowFigure 2. Differences between complementary, alternative, and integrative treatment. A, Complementary therapies are used along with standard medical treatment. B, Alternative therapies are used instead of standard medical treatment. C, Integrative medicine uses standard medical treatment along with evidence-based complementary and alternative therapies.

To analyze the current evidence on the effects of aromatherapy as a complementary therapy in pain management, a review of the literature was carried out using the databases PubMed/Medline and CINAHL with the key terms: "aromatherapy" and "pain management." Only primary research studies published in English from 2012-2018 were selected for this review. Exclusion criteria included secondary research and case studies. Studies that only measured other symptoms, such as fatigue or mood, were excluded. Initial searches on PubMed/Medline and CINAHL identified 60 manuscripts using the key terms. Of these, 40 were excluded because they were review articles, or did not measure pain. We provide, next, a description of each study and evaluation of the conclusions from the research findings.

 

Aromatherapy for Pain in Infants

In a quasiexperimental trial, a sample of 40 infants between 2 and 6 weeks of age and gestational age between 38 and 42 weeks who all exhibited signs of colic was randomized to an aromatherapy massage intervention (n = 20) or control group (n = 20) to evaluate the effectiveness of aromatherapy massage on infantile colic.10 The mothers of infants in the treatment group received aromatherapy massage training and were instructed to perform the abdominal massage within 1 to 2 minutes of the onset of a colic attack and to continue the massage for 5 to 15 minutes. The control group did not receive intervention.

 

All infants were monitored once a week by the research team for a total of 5 visits. The effect of the aromatherapy massage was measured by the length of time the infants cried per week. Results demonstrated that the intervention group had a statistically significant reduction in crying time from the preliminary observation for each subsequent observation over 4 weeks (all P < 0.01).

 

The authors concluded that the use of lavender oil was effective in reducing the symptoms of colic. However, there are several weaknesses of the study, with the major weakness being the lack of an attention control group, which could have included massage without an essential oil component. Because massage itself may be therapeutic for infantile colic, the study does not necessarily support aromatherapy as a mechanism of pain relief.

 

A randomized clinical trial to evaluate the scent of lavender on pain behavior and crying time was performed among 80 term neonates who were allocated to the intervention (n = 40) or control (n = 40) group.11 The night before venous blood sampling, infants in the intervention group were exposed to the scent of lavender for 8 hours by placing 10 drops of 0.5% lavender essential oil on a sterile gauze in the incubator at 10 cm from the neonate's head. At the time of blood sampling, the infant was exposed to the lavender scent. The Douleur Aigue Nouveau-ne (DAN) scale was used to measure behavioral pain response. Duration of crying in seconds from the start of crying to silence was recorded. The control group did not receive any intervention. The DAN scores showed a significant reduction in pain in the intervention group (P = 0.001) compared with the control group; however, there was no difference in time of crying between groups.

 

In another randomized controlled trial (RCT), 135 neonates with icterus were allocated to a familiar scent group (n = 45), an unfamiliar scent group (n = 45), and a control group (n = 45).12 The familiar scent group was exposed to vanillin (0.64 g diluted in 100-mL 85% glycerol) by placing 10 drops on a sterile gauze in the incubator at 10 cm from the neonate's head for 8 hours the night before arterial puncture. For neonates in the unfamiliar scent group, the familiarization was not carried out but blood sampling was done in the presence of the vanillin scent. The duration of crying in the familiar scent group was significantly lower than in the other 2 groups (P < 0.001); however, there were no differences in change in heart rate and blood oxygen saturation from baseline between groups.

 

Across the studies described previously, the standard of care for treatment of colic or painful procedures in neonates should be explained and provided to both groups (intervention and control), whether it is skin-to-skin contact, kangaroo care, or nutritive or nonnutritive sucking. All of these methods for reducing procedural pain are recommended over no intervention.13

 

Aromatherapy for Painful Procedures in Children and Adults

In a study to evaluate inhalation aromatherapy as a means of reducing pain associated with IV catheter insertion, Bikmoradi et al14 assigned 30 preschool children to receive 5 drops of lavender essence and 30 children to a control group who each inhaled 5 drops of distilled water 20 minutes before venipuncture. The Oucher scale was used to assess pain severity immediately, and again at 5 and 10 minutes after catheterization. Pain severity between the aromatherapy and control groups was significantly reduced in the experimental group at all time points (immediately P = 0.002; 5 minutes P = 0.001; 10 minutes P = 0.01).

 

In a randomized clinical trial, 106 patients were randomized to receive aromatherapy with lavender essential oil (n = 53) or placebo (n = 53) during peripheral vein cannulation.15 The perioperative care room nurse placed either 2 drops of 1% lavender essential oil or pure water on a 5-by-5 cm impermeable gauze pad and asked the participant to inhale for 5 minutes while in a seated position. After peripheral cannulation in the right hand, the participants were evaluated for pain, anxiety, and satisfaction. The intervention group reported significantly lower pain (P = 0.01), lower anxiety (P < 0.001), and higher satisfaction (P = 0.003), compared with the control group.

 

In an open crossover study among 34 hemodialysis patients with arteriovenous fistulae, the intensity of pain was measured in all the patients in 3 different conditions during insertion of arterial needles for hemodialysis: the topical application of 100% lavender essential oil, no intervention, and placebo with water.16

 

The 3 conditions were randomized. There was a minimum 72-hour interval between the intervention, and each participant had only 1 nurse who inserted the needles. For the topical application method, 3 puffs of 100% lavender essential oil were sprayed on the puncture site and left for 5 minutes. The same procedure was used for placebo. The intensity of pain was assessed after the arterial needle was inserted and before inserting the venous needle. The participants reported a significantly lower pain intensity score, measured by the numeric rating scale, with use of the lavender oil compared with no intervention or placebo (P = 0.001).

 

A double-blind placebo-controlled randomized study was conducted to evaluate inhalation aromatherapy using bergamot essential oil on anxiety, nausea, and pain among 37 pediatric participants with malignant and nonmalignant conditions undergoing stem cell infusion.17 The Spielberger State-Trait Anxiety Inventory was used to assess anxiety, whereas the visual analog scale was used to assess nausea and pain.

 

Diffusion of 4 drops of essential oil per hour with a stream of air from a fan placed by the child's bedside was used to deliver the intervention. The placebo control group received a non-essential oil-based scented shampoo in its fan. The same amount of essential oil was used regardless of the age or weight of the child. The treatment group experienced greater anxiety (P = 0.05) and nausea (P = 0.03) 1 hour postinfusion. Reported pain in both groups was not significantly different at 1 hour postinfusion. The authors note that bergamot essential oil causes a dose-related sequence of sedative and stimulatory behavioral effects, which may have confounded the study findings.

 

Among 73 hospitalized children with well-controlled type 1 diabetes, aromatherapy was used in a room during self-monitoring of blood glucose and compared with a group that did not receive aromatherapy.18 The child's pain intensity was measured by visual analogue scale and change in baseline heart rate. Aromatherapy did not alter the visual analog scale score. However, after adjustment for the patient's age and sex, lower change in heart rate was associated with the aromatherapy (P = 0.025). The authors concluded that aromatherapy decreased the autonomic response to a painful stimulus by lowering the change of baseline heart rate, but it did not affect the perception of pain.

 

Although the studies evaluating aromatherapy for procedural pain provide some compelling findings of decreased pain, they also suffer from not explaining standard-of-care procedures for pain relief in the control groups. Although it is possible that the institutions at which the studies were conducted do not provide any preemptive procedures for pain relief, such as thermal, mechanical, or anesthetic interventions for venipuncture or catheter insertion, future studies should contemplate using a best-practice control group versus standard care.

 

Aromatherapy for Menstrual Pain and Premenstrual Syndrome

The effect of aromatherapy massage on menstrual pain was evaluated in 55 school-age girls.19 The participants were divided into the experimental group (n = 32) or control group (n = 23) according to their preferences. The experimental group received a 10-minute aromatherapy massage of the abdomen 1 time using clary sage, marjoram, cinnamon, ginger, and geranium in a base of almond oil. The control group self-administered acetaminophen as usual. The level of pain severity was assessed using a visual analogue scale at baseline and 24 hours after the intervention. Aromatherapy massage was strongly associated with reduction of pain ([beta] = -3.07, 95% confidence interval -3.83 to -2.29, t = -8.00, P < 0.001), followed by the baseline value of level of pain ([beta] = -0.69, 95% confidence interval -1.07 to -0.31, t = -3.69, P < 0.001). This difference favored the treatment group. The limitations of the study included a high dropout rate in the aromatherapy massage group (10 subjects) and nonrandomized methods.

 

Premenstrual syndrome (PMS) is a set of physical and psychological symptoms that begin approximately 1 week before menstruation. An RCT was used to determine the effect of aromatherapy on coping with PMS in university students.20 For the study, 77 students were recruited and randomized to the experimental group (n = 40) or control group (n = 37), and all participants were followed up for 3 cycles in terms of PMS symptoms. One-to-one training was provided to intervention group participants about aromatherapy and how to use it. Intervention group participants were provided with 10 mL of lavender oil and a dropper. They were instructed to begin aromatherapy at least 10 days before the beginning of their menstrual cycle and use it once a day at the same hour, and to stop it when their periods started.

 

Aromatherapy was self-administered using 3 drops of lavender oil in 200 mL of hot water and covering the participant's head with a towel in a sitting position and inhaling the steam. The control group continued with their normal self-care. The Premenstrual Symptoms Scale was used to assess the primary outcome. There was a significant reduction in the PMS score in the intervention group compared with the control group (P < 0.05), with a significant reduction in pain, anxiety, depressive affect, nervousness, bloating, and depressive thoughts (all P < 0.05).

 

In addition to methodologic concerns, these studies could be strengthened by controlling for analgesic use and other symptoms experienced by the participants. In addition, standard education for self-care and other elements of standard care should be explained.

 

Aromatherapy for Pain in Labor and Postpartum Pain

An RCT to analyze the effects of aromatherapy with Rosa damascena on pain and anxiety in the first stage of labor among 110 nulliparous women was recently conducted.21 Participants received 0.08 mL of R. damascena essence in the aromatherapy group and 0.08 mL of normal saline in the control group, every 30 minutes from the time of cervical dilation to 4 cm until childbirth. Essential oil of the rose plant was obtained by water distillation and was diluted to 2% in sesame oil. Pain was measured 3 times, once at each stage of cervical dilation (4-5, 6-7, and 8-10 cm) via the numerical pain rating scale. Pain severity and anxiety in the experimental group were significantly lower than in the control group at each assessment (all P < 0.05).

 

Aromatherapy was also evaluated among 104 laboring primigravidae who were low risk, with single pregnancies during the latent and early active phase.22 The experimental group (n = 52) was offered 4 options of aromas to choose: lavender, geranium rose, citrus, or jasmine. Aroma oil was diffused continuously by aroma diffusers using standard concentration at 4 drops of oil per 300 mL of diffused water. The aromatherapy was started when participants were admitted for labor until the end of the first stage of labor. The control group (n = 52) received standard care. Pain severity was assessed using the numerical rating scale. The mean differences of pain scores between latent and early active phase and baseline were significantly lower in the aromatherapy group (P = 0.01 and P = 0.03, respectively). Late active phase pain scores and other perinatal outcomes were not significantly different.

 

A single-blind randomized clinical trial was conducted among 120 pregnant women who were randomized to the experimental group who received 2 drops of lavender essence inhaled during 3 stages (4-5, 6-7, and 8-9 cm of cervical dilation; n = 60) or a placebo control group (n = 60).23 Pre- and postintervention pain scores, measured by the numeric pain scale, were obtained during each stage. The results demonstrated no difference in pain scores during the early stage (4-5 cm) but a significant decrease in pain during the second and third stages in the aromatherapy group compared with the placebo group (P < 0.001). There was no effect on the mean duration of the active phase of labor.

 

Lavender oil was also evaluated for its effect on pain, fatigue, and mood during the early hours of the postpartum period among mothers.24 An RCT was conducted among 56 participants who were randomized to the intervention group (n = 29) or control group (n = 27). The intervention group received lavender oil in 3 doses during the first 24 hours after delivery, whereas the control group received sesame oil. For the intervention, 5 drops of lavender essential oil were placed on a cotton ball and the participant was asked to hold it about 20 cm from her nose for 10 to 15 minutes and to breathe normally. This was repeated 6 hours after the initial intervention and at bedtime. Pain, fatigue, and distress level were measured using the visual analog scale and mood was assessed with the Positive and Negative Affect Schedule. After the first intervention and the morning assessment, the intervention group reported significantly lower perineal pain (P = 0.004, P < 0.001), physical pain (P < 0.001), fatigue (P = 0.02; P < 0.001), distress (P < 0.001), and negative mood (P = 0.007, P < 0.001). Repeated-measures analyses demonstrated that the 2 groups were significantly different over time in pain, fatigue, and mood.

 

These studies provide compelling evidence on the effects of aromatherapy for labor pain and anxiety. Each of the studies explained standard of care and provided information necessary to evaluate the strength of the evidence.

 

Aromatherapy for Postoperative, Musculoskeletal, and Neuropathic Pain

Among 48 posttonsillectomy patients age 6 to 12 years, an RCT was conducted with random assignment to an inhaled lavender essential oil intervention group (n = 24) or a standard care control group (n = 24).25 All patients received acetaminophen (10-15 mg/kg/dose) by mouth every 6 hours as needed for pain relief. Pain intensity, the frequencies of daily use of acetaminophen, and nocturnal awakening due to pain were recorded for each patient for 3 days after surgery. This study found that inhaled lavender did not have any effect on pain intensity or frequency of nocturnal awakening, although there was a statistically significant reduction in daily use of acetaminophen in the intervention group (P < 0.05 on day 1; P < 0.001 on days 2 and 3).

 

An RCT among 60 participants with a history of neck pain was conducted to assess the efficacy of aromatic essential oils on neck pain.26 The experimental group (n = 30) received a cream composed of 4 essential oils-marjoram, black pepper, lavender, and peppermint-and were instructed to apply 2 g of cream directly to the affected area daily after showering or bathing until fully absorbed. The control group (n = 30) received an unscented cream. The visual analogue scale, Neck Disability Index, pressure pain threshold, and neck-joint range evaluated with a Motion Analysis System were used to evaluate outcomes. In both groups, pain severity decreased from baseline to posttreatment (P < 0.05). However, the experimental group had lower disability, higher pain tolerance in the left and right upper trapezius, and significant improvement in 10 motion areas.

 

Among community-dwelling older adults with chronic pain, a 4-week aromatherapy program was analyzed for effects on pain, depression, anxiety, and stress.27 For this study, 82 participants were assigned to the intervention group (n = 44) or control group (n = 38). The 4-week intervention consisted of 4 center-based sessions and self-administered home-based sessions. The center-based sessions were held once per week in community centers to provide knowledge on pain, pain in older persons, and aromatherapy.

 

In the sessions, lavender and bergamot essential oils were administered by inhalation. The self-administered home-based aromatherapy consisted of an aromatic spray with diluted lavender and bergamot essential oils and lavender hydrolats. A demonstration and a return demonstration were carried out to ensure that the participants knew how to use the spray correctly. There was a slight reduction in the pain score of the intervention group and a significant reduction in negative emotions compared with the control group. Significant differences were found between the intervention and control groups on depression, anxiety, and stress scores at postintervention (P < 0.05). In addition, the intervention group had a significant reduction in depression, anxiety, and stress scores from baseline to postintervention (P < 0.05).

 

In an open-label RCT, 46 patients with neuropathic pain associated with diabetes were randomly allocated to an intervention group (n = 21) or control group (n = 25).28 The intervention group received aromatherapy massage 3 times per week for a period of 4 weeks, whereas the control group received routine care. The Douleur Neuropathique 4 (DN4) questionnaire, visual analog scale, and Neuropathic Pain Impact on Quality of Life questionnaire were used to assess the primary outcome of pain severity and quality of life. The groups were similar in terms of duration of diabetes, HbA1c level, and treatment for neuropathy. A blended oil mixture was used for the aromatherapy consisting of rosemary, geranium, lavender, eucalyptus, and chamomile in a coconut carrier oil in a 5% solution. The duration of each massage was 30 minutes, with 20 minutes for the feet and 10 minutes for the hands. At week 4, neuropathic pain scores significantly decreased in the intervention group compared with the control group (P = 0.0001) and quality of life increased significantly (P = 0.049). The authors concluded that aromatherapy massage is an effective intervention to improve pain and quality of life in patients with painful diabetic neuropathy.

 

These studies provide further evidence on the effects of aromatherapy on mood and quality of life. Although effects on pain intensity are not consistent, the studies document other outcomes (such as decreased analgesic use, decreased depression, anxiety, and improved quality of life) that are important to patients.

 

Systematic Review of Aromatherapy for Pain Management

In a meta-analysis of 3 RCTs that evaluated aromatherapy massage for reducing cancer pain, the authors reported no significant effect.29 The studies included 278 participants (135 in the massage with essential oil group and 143 in the usual care control group). A systematic review of 9 RCTs (644 participants) analyzed the effectiveness of aromatherapy for reducing postoperative pain.30 Of these, 5 of the studies reported a statistically significant reduction in pain compared with usual care, whereas 4 studies showed no difference in pain severity between the experimental and control groups. Limitations of the systematic review include the wide variability of interventions (types of essential oils, concentrations, and applications), operations, and anesthesia types.

 

A systematic review and meta-analysis of 12 studies that analyzed the effectiveness of aromatherapy for pain management was conducted in 2016.31 The authors reported a significant positive effect of aromatherapy in reducing pain severity compared with placebo or treatment as usual controls. The meta-analysis supported that the effectiveness of aromatherapy is more consistent for nociceptive and acute pain, especially postoperative pain and obstetrical and gynecologic pain, compared with inflammatory or chronic pain.

 

Conclusion

Aromatherapy as a complementary intervention in pain management seems to have beneficial effects on pain severity in some studies, and positively influences mood and quality of life. As the emotional aspects of pain can either facilitate or inhibit pain severity, future studies should integrate affective measures to provide a more thorough evaluation of the effects of aromatherapy. In addition, standard care for the management of pain should be clearly described and implemented in the control groups. The pleasantness of the intervention and expectations of the participant should be analyzed in future studies to further decipher the mechanisms by which aromatherapy influences pain perception and management.

 

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Aromatherapy; Essential oils; Odor; Pain management