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A Brief Review of Current Scientific Evidence Involving
Aromatherapy Use for Nausea and Vomiting
Pei Lin Lua, PhD, and Noor Salihah Zakaria, BSc
Abstract
Objectives: The objective of this study was to compile existing scientific evidence regarding the effects of
essential oils (EOs) administered via inhalation for the alleviation of nausea and vomiting.
Methods: CINAHL, PubMed, and EBSCO Host and Science Direct databases were searched for articles related to
the use of EOs and/or aromatherapy for nausea and vomiting. Only articles using English as a language of
publication were included. Eligible articles included all forms of evidence (nonexperimental, experimental, case
report). Interventions were limited to the use of EOs by inhalation of their vapors to treat symptoms of nausea
and vomiting in various conditions regardless of age group. Studies where the intervention did not utilize EOs
or were concerned with only alcohol inhalation and trials that combined the use of aromatherapy with other
treatments (massage, relaxations, or acupressure) were excluded.
Results: Five (5) articles met the inclusion criteria encompassing trials with 328 respondents. Their results
suggest that the inhaled vapor of peppermint or ginger essential oils not only reduced the incidence and severity
of nausea and vomiting but also decreased antiemetic requirements and consequently improved patient satis-
faction. However, a definitive conclusion could not be drawn due to methodological flaws in the existing
research articles and an acute lack of additional research in this area.
Conclusions: The existing evidence is encouraging but yet not compelling. Hence, further well-designed large
trials are needed before confirmation of EOs effectiveness in treating nausea and vomiting can be strongly
substantiated.
Introduction
Nausea and vomiting are symptoms that can be caused
by various diseases and certain life events such as
pregnancy.
1
Depending on the underlying pathogenesis,
these symptoms may appear in acute or chronic form. Nausea
is defined as an unpleasant sensation around the throat, upper
gastric region, or abdomen or commonly described as feeling
‘‘sick to the stomach.’’
2
Vomiting or emesis can be denoted as
‘‘throwing up’’ (the forceful expulsion of the stomach contents
through the oral or nasal cavity).
2
The frequent number of
occurrences of nausea and vomiting sometimes cause these
symptoms to be regarded as inconvenient or a nuisance rather
than being seen as a medical problem. Failure to address the
focal issues of these symptoms can be debilitating, causing
unnecessarily prolonged recovery times, and may eventually
lead to serious complications such as pneumonia, dehydra-
tion, and malnutrition.
3
To date, the main pharmacological intervention for nausea
and vomiting involves antiemetic prescription. Considerable
progress has been made in antiemetic therapy, particularly
with the use of a 5-HT
3
receptor antagonist, a highly effective
antiemetic, particularly beneficial for high-risk patients,
especially chemotherapy and radiotherapy recepients.
4
Nevertheless, despite the availability of this modern treat-
ment, nausea and vomiting remain among the most common
symptoms experienced by a large number of patients in
medical conditions such as postoperative, chemotherapy,
and radiotherapy recipients, with the reported incidence
reaching to over 50% of the populations.
5–7
Self-care reme-
dies such as drinking ginger or peppermint teas, eating bland
foods, and relaxation have been commonly attempted, es-
pecially for temporary or mild nausea and vomiting.
3,8
Un-
fortunately, nausea and vomiting can also impose negative
impacts on the quality of life (QoL),
9
thus warranting greater
attention to improve patients’ health outcomes. With an
emphasis on improvements in current practices along with
the increasing demand for holistic care, the integration of
complementary therapies into mainstream treatment may
help to achieve desirable patient outcomes.
Centre for Clinical and Quality of Life Studies, Faculty of Medicine and Health Sciences, Universiti Sultan Zainal Abidin, Terengganu,
Malaysia.
THE JOURNAL OF ALTERNATIVE AND COMPLEMENTARY MEDICINE
Volume 18, Number 6, 2012, pp. 534–540
ªMary Ann Liebert, Inc.
DOI: 10.1089/acm.2010.0862
534
Aromatherapy refers to the therapeutic use of fragrant
substances, called essential oils (EOs), to help improve
physical and mental health and QoL
10
and represents a
possible form of complementary and alternative medicine
(CAM) for nausea and vomiting. EOs are usually obtained
by steam distillation of aromatic plants,
11
whereas other
kinds of extracts that are not obtained by steam distillation
are not considered as EOs.
12
Different aromatic plants pro-
duce EOs with different fragrance and therapeutic charac-
teristics depending on their chemical constituents.
13
For
example, lavender (Lavandula angustifolia) and its main con-
stituents, linalyl acetate and linalool, exhibit local anesthetic
effects in animal in vitro models.
14
Additionally, in other
animal studies, a-bisabolol from chamomile (Matricaria re-
cutita) EOs was identified as having strong anti-inflamma-
tory effects.
15
The main therapeutic properties of EOs also
include antiseptic, antibacterial, wound-healing, immune-
stimulant, as well as calming, sedative, analgesic, uplifting,
and stimulating effects.
16
For thousands of years, aromatherapy has been used in
countries such as Egypt and India as an ancient tradition of
herbal medicine.
17
Aromatherapy could be applied either
through inhalation of fragrances, topical application (with
or without massage enhancement), or both. In France, the
practice of medical aromatherapy involves internal use (in-
gestion) of EOs
15
such as the consumption of peppermint
(Mentha piperita) oils for gastrointestinal disorders to reduce
colonic spasm during colonoscopy
18
and the symptoms of
irritable bowel syndrome.
19
Other than that, EOs can also be
diffused in the air, added in the warm bath water, or used in
plant poultices or compresses. However, for the purpose of
this review, the focus is on the therapeutic use of EOs pri-
marily via inhalation of its vapors. Due to its advantage of
being a noninvasive and relatively low-risk treatment, aro-
matherapy could serve as a promising modality to improve
patient care.
20
However, with the advances of evidence-
based medicine, empirical research is consistently required to
evaluate the efficacy of this treatment modality. For the time
being, substantial evidence for clinical trials on aromather-
apy is limited to relaxation alone.
15
Despite the limited clinical evidence, there are encourag-
ing indications from basic science research that certain EO
vapors are absorbed by inhalation and alter brain func-
tion.
21–23
Herz
24
proposed two hypothetical mechanisms for
the effects of odors on mood, behavior, and physiology:
pharmacologic and psychologic mechanisms. Pharmacolo-
gically, the fragrances of EOs may deliver direct effects on
the central/ autonomic nervous system and endocrine sys-
tem regardless of conscious evaluation. Following inhalation,
volatile EO molecules pass to olfactory receptors in the nose,
which recognize their molecular characteristics, and send
signals to the brain via the olfactory nerve. In addition, some
of the constituents pass into the bloodstream via the lungs
and consequently produce their effects directly on brain
neurons after passing through the blood–brain barrier.
25
Apart from that, based on psychologic hypothesis, the po-
tential effects of smell depend on emotional learning, con-
scious perception, as well as belief and expectations. As such,
the perceived quality of the odors is also accountable for the
individual responses.
Although aromatherapy represents the most regularly
practiced CAM modality by users, it is also one of the least-
researched therapies. At the present time, there are no re-
views for aromatherapy on the Cochrane database.
26
A new
review is in process as a team is updating the review and
preparing a protocol to evaluate the effectiveness of aroma-
therapy for postoperative nausea and vomiting
26
(this was
also confirmed through personal communication with the
main author). As such, the objective of the current review is
to compile the currently available scientific evidence on the
effects of aromatherapy for nausea and vomiting.
Methods
The authors sought to identify all clinical trials and re-
views involving the therapeutic use of inhaled aromatherapy
to alleviate nausea and vomiting. Eligible articles included all
forms of evidence (nonexperimental, experimental, case re-
port). Interventions were limited to the use of EOs by vapor
inhalation to treat symptoms of nausea and vomiting in
various conditions regardless of age group. Studies where
the intervention did not utilize EOs or were concerned with
only alcohol inhalation and trials that combined the use of
aromatherapy with other treatments (massage, relaxations,
or acupressure) were excluded. An inclusive search for
clinical research was carried out in major biomedical, nurs-
ing, and specialist CAM databases such as CINAHL,
PubMed, EBSCO Host, and Science Direct. The search en-
compassed all articles published by the end of November
2010. The basic search terms used included aromatherapy,
essential oils, scent, fragrance, nausea, vomiting, and com-
plementary therapy. In order to obtain the widest range of
studies, no limit was set for the date of publication. In ad-
dition, the bibliographies of the located studies were scanned
for further relevant studies. Nevertheless, only articles using
English as a language of publication were included in this
review. Further information on unpublished and ongoing
research was traced using relevant databases such as Clin-
icaltrials.gov (US). Figure 1 shows the flow of the literature
search process.
Results
All reviewed studies are summarized in Table 1. The
searches identified four clinical studies and one review article
involving a total of 328 study participants. Three (3) studies
investigated postoperative nausea and vomiting (PONV) and
one study focused on oncology nausea and vomiting. All
studies concluded that inhaled aromatherapy served as an
effective treatment for the nausea and vomiting. Other con-
siderations for practical use of aromatherapy included the
reduction in antiemetic requirement such as prochlorperazine,
droperidol, ondansetron, or metoclopramide, increased pa-
tient satisfaction, and improved cost effectiveness.
These studies varied from simple observational studies to
the use of a randomized controlled trial. The outcomes
evaluated included PONV and oncology nausea. Visual an-
alog scale (VAS), standard descriptive ordinal scale, nausea
section of the Edmonton Symptom Assessment System
(ESAS), as well as the reported incidence were the instru-
ments used to measure the intended outcomes. In the An-
derson and Gross
5
trial, a 100-mm VAS was rated by the
respondents at 2 and 5 minutes postintervention. A study
by Tate
27
collected the information related to nausea on a
4-hourly and 12-hourly basis.
AROMATHERAPY FOR NAUSEA AND VOMITING 535
The interventions also differed as evidenced by the use of
a variety of EOs. In two studies, peppermint oil was used for
nausea and vomiting treatment in the experimental
group.
5,27
Specifically in one trial, patients were asked to
inhale the vapors deeply through the nose three times from a
scented gauze pad held directly under their nostril, then to
exhale slowly through the mouth.
5
In another study, con-
senting patients were also offered peppermint oils that were
administered through the inhaler for 5 seconds.
28
Geiger
25
used ginger essential oil in his study in which 5% Zingiber
officinalis (ginger) in grape-seed oil was applied below the
nose immediately before surgery. Additionally, the solution
was put on the pulse-points of both wrists for patients to
sniff if they experienced nausea postoperatively. The Stringer
and Donald
29
trial employed a personalized aromatherapy
inhalation device, known as Aromastick, whereby a choice of
two blends of essential oils was available for patients to
choose. One of the revealed blends consisted of peppermint
and lemon (Citrus limonum). This device was held by patients
approximately 6 inches under their nose while breathing in
and it could be used as necessary, allowing self-symptom
management.
Three (3) studies of controlled trials reported using dif-
ferent controls or placebos. Geiger
25
and Tate
27
compared
their aromatherapy intervention to a no-treatment group.
Additionally, peppermint essence was also used in the study
by Tate
27
in his three-arm evaluations to assess the efficacy of
peppermint EOs for PONV. Conversely, the respondents in
the Anderson
5
trial were provided with placebo gauze pads
prepared by placing 2 mL of isotonic saline.
A substantial number of patients had reported the benefits
of using aromatherapy. This was evidenced by 82% of re-
spondents indicating the benefits of Aromasticks for nausea
management whereby almost half (47%) settled their nausea
problem.
29
Another study also showed that 80% of high-risk
patients did not experience PONV after the application of
5% ginger EOs nasocutaneously.
25
In addition, self-reported
nausea score was significantly different between the placebo
and experimental groups.
27
Despite overall nausea score
decreasing significantly after aromatherapy administration,
the reduction was independent of treatment
5
attributed to
the favorable effects of controlled breathing patterns.
Discussion
Study outcomes
The overall findings from the reviewed studies suggest
that aromatherapy can offer beneficial effects for nausea and
vomiting. However, there are very few published research
articles as well as apparent methodological flaws on this
subject matter, providing room for improvement. Most of the
studies included had examined the efficacy of aromatherapy
on PONV patients, enabling the possibility of evaluating its
effectiveness for various types of clients. However, they were
confined only to limited sample sizes (n=17–160) and their
study designs were not entirely satisfactory. Difficulties in
recruiting and retaining patients were problems common to
all clinical trials due to the use of broad exclusion criteria and
inadequate outreach to populations such as individuals with
low income, ethnic minorities, and the elderly.
30
This factor
would limit the patient participation and clearly reduce
generalizability. With only one study adopting a randomized
control design,
5
attempts to evaluate the actual clinical ben-
efit of this complementary therapy remain challenging.
Placebo/control
Selecting the appropriate placebo for aromatherapy in-
tervention can be difficult. Wiebe
31
suggested that the con-
trol for CAM trials should sufficiently mimic active
treatment to support the blinding of patients.
32
For instance,
the study by Tate
27
used a fragrance-matched artificial pla-
cebo (peppermint essence) as a comparator, lacking in
menthol composition compared to peppermint EOs. Most
aromatherapists believe that synthetic fragrances are inferior
to EOs, although they are often composed of many of the
same compounds.
33
This is because synthetic fragrances lack
natural or vital energy; however, this has been contested by
odor psychologists and biochemists who believe in the im-
portance of therapeutic odor in treating various illnesses.
34
Menthyl acetate, which is responsible for peppermint’s
minty aroma and flavor,
35
might also be favorable in nausea
conditions. However, because adaptation to the odorant oc-
curs quickly (in which the smell receptors become less re-
sponsive to respond to repeated or continued stimuli of
constant odor intensity), this condition reduces the potency
of the odor to treat an ill condition, thus supporting the
pharmacologic effects of EOs.
34,36
Therefore, the respondents
could be blinded by using peppermint essence, since the
smell was similar except it was devoid of the active thera-
peutic compound in peppermint essential oils (menthol).
However, an experienced practitioner might be able to dis-
tinguish the differences considering the lack in menthol in
peppermint essence, hence moderating its cool sensation
properties. As such, the evaluation on the blinding may give
valuable information, especially in adopting a double-blind
study design. For instance, Graham et al.
37
revealed that
their attempts to blind patients for aromatherapy interven-
tion were not 100% effective, although most were uncertain
FIG. 1. The flow in the literature search process.
536 LUA AND ZAKARIA
Table 1. Scientific Evidence on Aromatherapy for Nausea and Vomiting
No.
First
author (year) Aims/purposes Sample Design/interventions
Outcome
measures Results Comments
1 Stringer
(2010)
To evaluate the
effects of a new
aromatherapy
intervention
using Aromastick
Oncology
patients
with
anxiety,
nausea and
sleep
disturbance
(n=160)
Retrospective service
evaluation
Aromastick was given to the
referred patients consisting
of a choice of 2 blends of
essential oils (of which one
combination =peppermint
+lemon; the other
unstated)
Frequency of
using
Aromastick
and
perceived
benefit
Reduced anxiety, nausea, sleep disturbance
with 47% of nauseous patients reported
fewer symptoms prior to the use of
Aromastick
Effect of Aromastick may be directly
proportional to the frequency of their use
No report on antiemetic use
No known side-effects
Non-randomized and
uncontrolled trial
No baseline measurement
was taken by validated
tools
Unable to rule out the
placebo effects
2 Buckle
(2007)
To discuss the
expansion of
aromatherapy,
particularly in
the field of
nursing
Nauseous
patients
(n=17)
A review paper; included
one controlled clinical trial
(CCT) assessing undiluted
peppermint oil in plastic
personal inhaler
Nausea
section of
the
Edmonton
Symptom
Assessment
System
Reduced nausea ( p<0.001) Small sample size
Secondary reference
3 Geiger
(2005)
To evaluate the
efficacy of 5%
ginger essential
oils
administered
nasocutaneously
to prevent
postoperative
nausea and
vomiting
(PONV)
Patients at
high risk for
PONV from
post-
anesthesia
recovery
unit (PACU)
(n=100)
CCT
1. Nasocutaneous
application of 5% ginger
essential oil (experimental)
applied on pulse points of
both wrists for patients to
sniff
2. Standard anti-emetic
treatment (control)
Incidence of
nausea and
vomiting
80% of high-risk patients had no complains
of PONV
No report on antiemetic use
No known side-effects
Nonrandomized trial
Unquantifiable control
variables
4 Anderson
(2004)
To determine the
efficacy of
aromatherapy
with isopropyl
alcohol or
peppermint oil
in nauseous
patients after
outpatient
surgery
Ambulatory
surgery
patients in
PACU with
PONV
(n=33)
Randomized control trial
Inhalation of 2 stacked 2†·2†
gauze pads containing:
1. 1 mL of 70% isopropyl
alcohol
2. 2 mL isotonic saline
+0.2 mL of peppermint oil
3. 2 mL isotonic saline
(placebo)
VAS 100 mm
severity of
nausea at 2
minutes
and 5
minutes
post-
intervention
and level of
satisfaction
Overall nausea score significantly decrease
but did not differ among treatment groups.
Overall patient satisfaction was significantly
correlated with the decrease in the nausea
score 5 minutes after aromatherapy
Reduced intravenous antiemetic use by
nearly 50% (droperidol, ondansetron, or
metoclopramide)
No known side-effects
Small sample size
No control group (without
active treatment)
5 Tate (1997) To evaluate the
efficacy of
peppermint oil
through
inhalation for
PONV
Gynecological
patients
with PONV
(n=18)
CCT
1. No treatment (control)
2. Peppermint essence
inhaled from bottle
(placebo)
3. Peppermint oil inhaled
from bottle (experimental)
Standardized
descriptive
ordinal
scale on
nausea at 4-
hour and
12-hour
intervals
Experimental group:
Lower prevalence and /or intensity of nausea
More tolerance to analgesia
Less requirement for antiemetics
(prochlorperazine, ondansetron, or
metoclopramide)
The cost of drug treatment was
considerably reduced by half
No known side-effects
No statistical significance
was detected for all
variables except less
incidence of nausea in
experimental group
compared to placebo
group
Nonrandomized trial with
small sample size
537
or wrong about the treatment they actually received.
Therefore, it is important for future trials to choose the ap-
propriate placebo as well as to conduct the blinding assess-
ment in order to minimize (if not eliminate) the placebo
detection effect.
Assessment methods
There were no standard and consistent measures to assess
nausea and vomiting. Three (3) studies measured the se-
verity of nausea either using the VAS, nausea section of
ESAS, or a standardized descriptive ordinal scale, whereas
another two studies only reported the incidence of the
symptoms. VAS is commonly used to measure a variety of
subjective responses including the assessment of ‘‘feeling.’’
38
Generally, it consists of a 100-mm-long line in which the
lower anchor end corresponds to ‘‘no symptom’’ and the
higher anchor end signifies ‘‘unbearable symptom.’’ Nausea
intensity measurement using VAS serves an advantage over
other methods, considering that continuous data have ratio
properties and are well suited for statistical analysis, unlike
categorical scales
38
in the nausea section of ESAS or stan-
dardized descriptive ordinal scale. This instrument is also
easy to be self-administered for the patients because of its
simplicity and speed of completion as well as being unhin-
dered by a language barrier.
39
However, the estimation of
nausea intensity with VAS requires an ability to transform a
complex subjective experience to a visual–spatial display,
which involves perceptual judgment and accuracy. Potential
investigator bias might also occur, since patients may require
lengthy instructions from trained staff before completion.
Despite these limitations, VAS may still serve as a useful self-
reported tool in assessing nausea and vomiting considering
individual subjective perception of these symptoms.
Essential oils (EOs)
Inconsistencies in terms of the type of EOs and how they
were delivered (including dose, blended or single oil used)
hampered comparisons between these studies. Peppermint
and ginger oils have been regularly used in the aroma-
therapy intervention for nausea, using various methods of
administration including oral preparations. The selection of
these EOs was associated with the role of their chemical
constituents, which help in the relief of gastrointestinal
symptoms.
24,26
Peppermint oils have been shown to be an
effective remedy for morning sickness, dyspepsia, and other
gastrointestinal complaints; its effectiveness is attributed to
its antispasmodic properties.
40
In addition, the botanical
form of ginger was often advocated as beneficial for nausea
and vomiting in various conditions including motion sick-
ness, pregnancy-induced and postoperative conditions.
41-42
On the other hand, aromatherapists particularly use the
EOs in a blend form, since they are believed to be more
effective as the therapeutic value is generated by the reac-
tion and balance of the oils’ constituents.
33
The evidence
from the Stringer and Donald
29
trial on the effectiveness of
blended EOs to reduce nausea and vomiting is still deba-
table, as its retrospective design prevented the exclusion
of various study biases. Considering these facts, the im-
portant issues mentioned need to be further explored to
maximize the potential benefits of EOs use via inhaled
aromatherapy.
Side-effects
No known side-effects prior to aromatherapy adminis-
tration were reported by these studies, suggesting the mini-
mal invasive property of these EOs. In fact, only a few
isolated cases of allergic reactions were documented in the
literature.
43
Yet, with its volatility and the skin’s absorbent
nature, some EOs do possess the potential to initiate allergic
reactions.
44
Aromatherapy oil should therefore not be con-
sidered as a safe alternative to existing pharmacotherapy
until rigorous safety trials have been completed. Concerning
inhalational aromatherapy, only one incidence of idiosyn-
cratic allergic reactions with Anthemis nobilis essential oils
was reported (after inhalation of one drop of smelling
strip).
44
This incidence was among two serious cases that
were indicated by the author after 10 years of teaching in
aromatherapy. Thus, although the reviewed studies had not
indicated any untoward incidences, the risk still exists, re-
quiring precautionary measures to minimize any unwanted
consequences from EOs use.
Outcomes on antiemetic use
The reported outcomes in these reviewed studies have
also highlighted the reduction in the use of analgesic and
antiemetic medications. These positive responses are of value
for extrapolating to gauge the benefits toward less inherent
expenses and potential side-effects related to the pharmacologic
interventions, although the claims were not based on validated
outcomes measures. Therefore, future trials are recommended,
which should include an analysis of medication use as a result
of aromatherapy administration as well as cost effectiveness
assessment related to this complementary treatment.
Limitations
Despite the rather captivating findings from this review,
there are several limitations that need to be mentioned.
First, only five articles were reviewed and more than half
of the studies used small sample sizes. Even though a thor-
ough research strategy was employed, it cannot be assured
that all relevant trials have been located. Second, although
all the studies have stated that the aromatherapy interven-
tion was administered via inhalation, the method and du-
ration varied widely, which may directly or indirectly
influence the outcomes. Third, due to the restriction im-
posed by the search selection criteria, only one study was a
randomized controlled trial, while the others were using a
quasi-experimental design. No scoring system or quality
assessment for data extraction was adopted for this review,
considering the subdued data and the small number of
available studies that satisfied the selection criteria. Al-
though the excluded studies are not displayed in this review,
the inclusion criteria had served as a precise tool in selecting
the articles through which non-peer-reviewed publications
such as dissertations and non-English articles were excluded.
Conclusions
In summary, it is concluded that inhaled aromatherapy
using peppermint and ginger EOs may have potential ben-
efits in alleviating nausea and vomiting in postoperative and
oncology patients. Although the overall outcomes seem
promising, methodological weaknesses such as small sample
538 LUA AND ZAKARIA
sizes, quasi-experimental design, imprecise measuring tools,
inappropriate placebo, and varied doses or methods of EOs
application restricted these studies, thus compromising any
concrete conclusion. Hence, studies of this nature need to be
further replicated and improved before confirmation of the
effectiveness of EOs in treating nausea and vomiting can be
strongly substantiated.
Acknowledgments
The authors would like to sincerely thank Associate Pro-
fessor Dr. Nik Mazlan Mamat, Dean, Kulliyyah of Allied
Health Sciences, International Islamic University Malaysia
(IIUM) for his support and guidance.
Disclosure Statement
No competing financial interests exist.
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Address correspondence to:
Pei Lin Lua, PhD
Centre for Clinical and Quality of Life Studies
Faculty of Medicine and Health Sciences
Universiti Sultan Zainal Abidin
Kampus Kota, Jalan Sultan Mahmud
20400 Kuala Terengganu
Terengganu 20400
Malaysia
E-mail: peilinlua@unisza.edu.my
540 LUA AND ZAKARIA