Lemon Oil and Nausea: What the Pregnancy Trials Tested

Two Iranian randomized trials, six years apart, tested lemon-scented inhalation against a placebo in pregnant women with nausea and vomiting, and both reported lower scores in the lemon arm from day 2. A 2015 Cochrane review of all interventions for early-pregnancy nausea still concluded that high-quality evidence was lacking for any of them. This article reads each source for what it tested and what it left out. It is not a recommendation to use this shop's oil, or any essential oil, in pregnancy: that question belongs to a midwife or obstetrician.

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First, the threshold that matters more than any trial

The NHS tells pregnant women to contact their midwife, GP or 111 if they cannot keep food or fluids down for 24 hours, have very dark urine or no urine for more than 8 hours, feel very weak, dizzy or faint on standing, have tummy pain or a high temperature, vomit blood, or are losing weight. Hyperemesis gravidarum, the severe form, can lead to dehydration or malnutrition and sometimes needs hospital treatment (NHS, vomiting and morning sickness). If that describes the situation, scent is not the next step. The NHS page's own self-help list includes avoiding foods or smells that trigger sickness, and it does not mention aromatherapy or essential oils.

Trial one: lemon against placebo, 100 women

Yavari Kia and colleagues (2014) randomized 100 pregnant women with nausea and vomiting, using block randomization, to inhale lemon essential oil or a placebo whenever they felt nauseated. Nausea, vomiting and retching were scored with the PUQE-24 scale for the 24 hours before treatment and then across four days of treatment. The groups differed significantly on day 2 (p = 0.017) and day 4 (p = 0.039), with the lemon group lower on both days. The title calls the trial double-blinded, and the authors concluded that lemon scent may help reduce nausea and vomiting of pregnancy (Iran Red Crescent Med J, 2014).

What the abstract does not give is as important: the number in each group, the concentration or amount of oil, and how the placebo and blinding worked. A person can usually smell the difference between lemon and an odorless placebo, so blinding is hard here (reasoning, not a statement from the paper). The abstract reports a between-group difference on two of the four treatment days (2 and 4), on a self-reported scale, with no follow-up beyond day 4.

Trial two: lemon plus peppermint, 90 women

Safajou and colleagues (2020) enrolled 90 pregnant women with nausea and vomiting at health centers in Birjand, Iran, between February 2015 and August 2016, and compared a combined lemon and peppermint inhalation with a placebo, scored with the PUQE-24 and the Fatigue Severity Scale. The groups did not differ before the intervention or on day 1; the differences became significant on days 2, 3 and 4. Within the aromatherapy group, symptom intensity changed over time (F(2,84) = 22.92, p < 0.001); in the placebo group it did not (F(2,78) = 0.26, p = 0.836) (Iran J Nurs Midwifery Res, 2020). The authors concluded the combination may reduce mild to moderate nausea and vomiting.

This is a blend. Its result cannot be assigned to lemon alone, and it does not show what lemon did separately. Both trials are small, scored by the women themselves, and followed for four days.

What the systematic reviews conclude, and when

ReviewWhat it coveredConclusion in the abstract
Matthews et al., Cochrane, 201541 trials, 5,449 women, nausea and vomiting up to 20 weeks; interventions include lemon oil, mint oil, vitamin B6 and antiemetic drugs; register search to January 2015"There is a lack of high-quality evidence to support any particular intervention"; the abstract does not give lemon-specific numbers
Mascarenhas et al., 202521 studies of aromatherapy for pregnancy symptoms (16 randomized, 5 quasi-experimental), Iran, Indonesia, Japan and TaiwanNausea and vomiting pooled SMD -0.92 (95% CI -1.09 to -0.74), across peppermint, bitter orange, lemon and mint; no certainty rating in the abstract; authors call for larger high-quality studies
Rafiei et al., 20265 studies of lemon essential oil aromatherapy, risk of bias by Cochrane RoB 2Quality low to moderate; most reported reductions on the PUQE scale; authors call it "an effective and safe complementary therapy" and also cite small samples, potential bias and weak methods

Sources: Matthews et al., 2015; Mascarenhas et al., 2025; Rafiei et al., 2026. The sources disagree in tone, and the dates explain part of it. The Cochrane search ended in January 2015, so it could not include the 2020 trial, and the abstract does not say whether the 2014 trial was among its 41. Rafiei's 2026 review is lemon-specific and newer, but it pools five small studies of low to moderate quality, and "safe" is the reviewers' word about a complementary therapy in general, not a statement this shop makes about any oil. Mascarenhas's pooled number blends several oils, so it is not a lemon figure.

A different setting, not a different answer

Lemon inhalation has also been tested for nausea after surgery. Sangi and colleagues (2026) randomized 104 patients having coronary artery bypass surgery to lemon inhalation or an odorless placebo, from the evening before surgery through 72 hours after extubation, and reported lower nausea and vomiting severity at all postoperative shifts (P < 0.001), with fewer vomiting episodes and less rescue antiemetic use (Iran J Pharm Res, 2026). The abstract does not give per-group sizes or exact scores. A hospital cardiac-surgery population is not a pregnant one, and the 2012 Cochrane review of aromatherapy for postoperative nausea pooled 9 studies and 402 participants, found isopropyl alcohol vapor beat saline placebo for needing rescue antiemetics (RR 0.30, 95% CI 0.09 to 1.00), found no reliable evidence for peppermint oil, and does not mention lemon (Hines et al., 2012).

What this shop will and will not say

The FDA regulates aromatherapy products by intended use, judged from labeling, websites and advertising, and lists claims such as helping you sleep or treating depression or anxiety as drug claims; it describes a therapeutic use, such as treating or preventing disease, as a drug use (FDA, aromatherapy). We sell one lemon oil, neat, as a scent material. We make no medical claim for it, we sell nothing for nausea, our copy says do not take it internally and keep it from children and pets, and we have no inhalation routine to give. Nothing here changes that: a small trial of inhaled lemon oil is not a recommendation to use ours.

Before using any essential oil while pregnant, ask the midwife or obstetrician who is looking after the pregnancy; a pharmacist can also answer questions about products. Our own pregnancy article reports what the authorities say: lemon oil during pregnancy and breastfeeding. For the safety basics see photosensitivity, dilution and kids, and for common questions the FAQ.

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Sources & Further Reading