We searched CENTRAL; MEDLINE; Embase; CINAHL; CAM on PubMed; Informit; LILACS; and ISI Web of Science as well as grey literature sources and the reference lists of retrieved articles up to March 2017. The original search was performed in August 2011.
SELECTION CRITERIA: Two review authors independently assessed risk of bias in the included studies and extracted data. For dichotomous outcome variables, we used a random-effects model and calculated risk ratio (RR) with associated 95% confidence interval (95% CI). For continuous outcome variables, we used a random-effects model and calculated standardized mean difference (SMD) with associated 95% CI. We used the GRADE software to compile 'Summary of findings' tables.
MAIN RESULTS: We included seven new studies with 663 participants in the 2017 update; five RCTs and two CCTs. These were added to the nine previously included studies (six RCTs and three CCTs with a total of 373 participants) for a total of 16 included studies and 1036 participants in this updated review. The mean age and range data for all participants were not reported for all studies. We identified two registered trials that met the inclusion criteria for this review; however there are no results for these studies yet.Overall, the GRADE assessment of evidence quality ranged from moderate to very low. The method of randomization in 11 of the 12 included RCTs was explicitly stated and adequate. Incomplete or methodologically diverse reporting of data affected the completeness of the analysis. Data on additional
aromatherapies were added in the 2017 update (blended
aromatherapy products, and peppermint products). Heterogeneity of outcome measures and time points between studies affected the completeness of the analysis.In the summary of the findings of six studies, we did not find
aromatherapy to be effective in reducing
nausea severity in comparison to placebo (SMD -0.22, 95% CI -0.63 to 0.18, P value = 0.28, 241 participants, level of evidence: low). Those participants receiving
aromatherapy were no more likely to be free of
nausea at the end of the treatment period than those receiving placebo (RR 3.25, 95% CI 0.31 to 34.33, P value = 0.33, 4 trials, 193 participants, evidence level: very low), however they were less likely to require rescue
antiemetics (RR 0.60, 95% CI 0.37 to 0.97, P value = 0.04, 7 trials, 609 participants, evidence level: low). There were no data reported on adverse events or patient satisfaction for this comparison.A specific comparison of peppermint
aromatherapy to placebo did not show evidence of an effect on
nausea severity at five minutes post-treatment in the pooled results (SMD -0.18, 95% CI -0.86 to 0.49, P value = 0.59, 4 trials, 115 participants, evidence level: low). There were no data reported on
nausea duration, use of rescue
antiemetics, adverse events or patient satisfaction for this comparison.When we pooled studies comparing
isopropyl alcohol to standard
antiemetic treatment in a GRADE summary of findings, in terms of
nausea duration, there was a significant effect on the time in minutes to a 50% reduction in
nausea scores (SMD -1.10, 95% CI -1.43 to -0.78, P value < 0.00001, 3 trials, 176 participants, evidence level: moderate). Fewer participants who received
isopropyl alcohol required rescue
antiemetics (RR 0.67, 95% CI 0.46 to 0.98, P value = 0.04, 215 participants, 4 trials, evidence level: moderate). Two studies with 172 participants measured patient satisfaction; there were high levels of satisfaction across both
aromatherapy and standard treatment groups and no differences found (evidence level: low). There were no data reported on
nausea severity or adverse events for this comparison.There was no difference in effectiveness between
isopropyl alcohol vapour inhalation and placebo for reducing the proportion of participants requiring rescue
antiemetics (RR 0.39, 95% CI 0.12 to 1.24, P value = 0.11, 291 participants, 4 trials, evidence level: very low). There were no data reported on
nausea severity,
nausea duration, adverse events or patient satisfaction for this comparison.
AUTHORS' CONCLUSIONS: Overall, for
nausea severity at the end of treatment,
aromatherapy may have similar effectiveness to placebo and similar numbers of participants were
nausea-free. However, this finding is based on low-quality evidence and therefore very uncertain. Low-quality evidence also suggests that participants who received
aromatherapy may need fewer
antiemetic medications, but again, this is uncertain. Participants receiving either
aromatherapy or
antiemetic medications may report similar levels of satisfaction with their treatment, according to low-quality evidence.