Inhaling Peppermint Essential Oil as a Promising Complementary Therapy in the Treatment of Nausea and Vomiting

Background: Nausea and vomiting frequently occur during postoperative recovery, chemotherapy, and pregnancy. While peppermint oil is traditionally used to relieve these symptoms, its efficacy remains uncertain. This systematic review and meta-analysis evaluates the efficacy of peppermint oil inhalation for postoperative (PONV), chemotherapy-induced (CINV), and pregnancy-related nausea and vomiting (NVP). Methods: Following PRISMA guidelines, we searched five databases (Scopus, Embase, the Cochrane Central Register of Controlled Trials, MEDLINE, and Web of Science) in November 2022, with an update in December 2024. Randomised controlled trials were included, comparing peppermint oil inhalation to a control in patients with PONV, CINV, and NVP. Separate meta-analyses were conducted for each patient group using R, focusing on the severity of the nausea and vomiting. Results: Nineteen RCTs were included. In three PONV studies, peppermint oil inhalation was associated with a reduction in nausea 2 to 6 h after the intervention (MD: -0.60 points, 95% confidence interval (CI): -0.77 to -0.44, p = 0.004). In three NVP studies, daily peppermint oil treatment was linked to lower symptom severity at 48 h (MD: -0.51, 95% CI: -0.78 to -0.24, p = 0.015) and 96 h (MD: -0.68, 95% CI: -1.09 to -0.27, p = 0.019). In three CINV studies, peppermint oil inhalation appeared to reduce symptoms at all time points, with the most notable reduction at 48 h (MD: -2.23, 95% CI: -3.13 to -1.34, p < 0.001) and 72 h (MD: -2.41, 95% CI: -3.96 to -0.86, p = 0.010). Conclusions: Peppermint oil inhalation may be a promising complementary therapy for reducing nausea and vomiting in postoperative, chemotherapy, and pregnancy settings.