Aromatherapy (Inhalation)

Parsa Tabei et al. (2025) · BMC complementary medicine and therapies

This randomized controlled trial with 92 breast cancer patients explored whether breathing in the scent of bitter orange (Citrus aurantium) essential oil could ease chemotherapy-induced nausea and vomiting (CINV) — sickness that standard anti-nausea drugs don't always fully control. CINV is typically split into an acute phase (the first 24 hours after treatment, driven mainly by serotonin release) and a delayed phase (roughly 1-5 days later, governed by different chemical signals including substance P). The study tested whether a simple, inhaled essential oil could specifically help with that harder-to-treat delayed phase. Ninety-two women undergoing AC-T chemotherapy for breast cancer (average age 48) were randomly assigned to inhale either bitter orange oil or a scentless sunflower-oil placebo — two drops on the upper lip, breathed in for 20 minutes, three times a day for five days, on top of their usual anti-nausea medication. Neither the patients, their nurses, nor the researcher analyzing the results knew who received which oil. Each day, patients rated their nausea, vomiting, and retching on the Rhodes Index, a validated 0-to-35 symptom scale. For the first two days, both groups fared about the same — expected, since standard medications already cover that early window well. But from Day 3 onward, the bitter-orange group pulled clearly ahead: by Day 5, their average total symptom score was roughly half the control group's (3.6 vs 7.1 out of 35, p=0.002), with similarly meaningful drops in vomiting (p=0.01), nausea (p=0.004), and retching (p=0.02) scores specifically. Within the aromatherapy group, symptoms dropped so much from Day 1 to Day 5 that the effect size was "very large" by conventional standards (Cohen's d=1.62 for total symptoms) — the placebo group barely moved at all over the same stretch. No one in either group reported side effects or discomfort from the oils. The pattern — no early benefit, a real one later — fits with what's known about the delayed phase of CINV being harder for drugs to reach and potentially more open to complementary approaches like aromatherapy. Because the trial didn't measure symptoms before treatment started and drew only from one clinic and one cancer type, these results need confirming in larger, more varied studies before bitter-orange aromatherapy becomes a routine recommendation — but as a cheap, safe add-on alongside standard antiemetics, the early signal here is encouraging.

Sahar Hamzeh et al. (2020) · Evidence-based complementary and alternative medicine : eCAM

This randomized controlled trial with 120 adult cancer patients explored whether breathing in lavender or peppermint essential oil before bed could ease the poor sleep that affects roughly a third of people with cancer. Sleep disruption in cancer care is often treated with sedative medications, which carry dependency risks, so researchers wanted a gentler alternative. Aromatherapy works through inhalation: aromatic molecules bind receptors in the nasal lining, sending signals to brain regions (the limbic system and thalamus) that release calming compounds like serotonin. Lavenders calming compounds are linalool and linalyl acetate; peppermints main compound, menthol, is thought to ease anxiety by damping stress-hormone release. Patients (average age 49, just over half women, most being treated for leukemia) at an oncology ward in Kermanshah, Iran were split into three equal groups of 40. For seven nights, the lavender and peppermint groups had three drops of their essential oil placed on a cotton ball pinned near the collar for 20 minutes before sleep; a masked control group got scented water instead. Everyone completed the Pittsburgh Sleep Quality Index (PSQI), a validated sleep questionnaire, before starting and again after the week was up. All participants started with poor sleep (average PSQI score of 12.62, where 5 or higher signals a problem). Sleep quality improved across all three groups over the week (p < 0.0001 for the change over time), and the pattern of improvement differed by group (interaction p < 0.001): 10% of patients using either lavender or peppermint reached good sleep quality by the end, versus 5% on the control. Even so, none of the direct group-to-group comparisons reached statistical significance -- lavender vs. control (p = 0.28), peppermint vs. control (p = 0.19), and lavender vs. peppermint (p = 0.82) -- meaning the trial could not statistically confirm that either oil outperformed the masked control, even though both intervention groups trended toward greater improvement. No adverse effects were reported from either oil. These results offer tentative, not definitive, support for lavender or peppermint inhalation as a low-cost, low-risk sleep aid alongside cancer care -- the trend favored both oils, but the comparison against a masked control did not reach statistical significance. Limitations include a study population with mixed cancer types and stages, unaccounted-for concurrent medications, and no report of cancer stage for many patients, all of which could affect sleep quality and treatment response. Larger trials with stage-matched groups and a truly unscented control are needed to determine whether either essential oil offers real benefit.

Dilek Yildirim et al. (2025) · Supportive care in cancer : official journal of the Multinational Association of Supportive Care in Cancer

This single-blind randomized controlled trial with 100 hospitalized adults explored whether inhaling lavender essential oil could ease two of the most disruptive symptoms of chemotherapy for blood cancer patients: fatigue and poor sleep. Fatigue here means a persistent, whole-body exhaustion that isn't relieved by rest and that chemotherapy drugs are known to intensify, while sleep quality captures how deep, continuous, and restorative a night's sleep actually is rather than just its duration. Lavender oil, extracted from a hybrid of two Mediterranean Lavandula species, is inhaled rather than ingested, working through its scent's effect on the brain's limbic system rather than any drug-like mechanism. Fifty adults with hematological cancers (multiple myeloma, leukemias, lymphomas) receiving chemotherapy in an Istanbul hospital were assigned to inhale two drops of lavender oil from a shoulder-pinned sponge for 20 minutes each night before bed, for five consecutive nights; another 50 received unscented saline the same way. Neither group knew which oil they were smelling. Fatigue was scored with the 22-item Piper Fatigue Scale and sleep with the six-item Richards-Campbell Sleep Questionnaire, both completed at baseline and again the morning after the fifth night. By night six, the lavender group's overall sleep score was meaningfully higher than the saline group's (70.80 vs. 59.16 out of 100, p = 0.001 — lavender users reported deeper, less interrupted sleep), with clear advantages in sleep depth, time to fall asleep, and number of awakenings. Fatigue told the same story in reverse: the lavender group's fatigue score dropped to 4.54 versus 5.51 in the control group (p = 0.001, lower is better), with the steepest improvements in the subscales measuring fatigue's effect on daily activities, physical sensations, and mental clarity. A statistical model combining lavender use and sleep score explained about 17% of the variation in how fatigued patients felt (R² = 0.171, p < 0.001) — a modest but real share, meaning sleep and scent worked together rather than independently. One subscale, emotional response to fatigue, improved but didn't quite reach statistical significance (p = 0.052). For hematology-oncology nurses, this points to an inexpensive, side-effect-free option — no adverse events were reported — that can be added to nightly care without special training or equipment. The trial only tracked five nights, so whether the benefit holds up over a full chemotherapy course is unknown, and the researchers grouped all blood cancer types together rather than testing whether effects differ by diagnosis. Larger, longer trials are needed before lavender aromatherapy becomes a standard recommendation rather than a promising adjunct.