The major chemical constituents of bergamot oil are linalyl acetate, limonene, linalool, and γ-terpinene. The components chiefly responsible for its flavor are linalool, citral, and linalyl acetate. Other constituents include β-pinene, α-pinene, sabinene, caryophyllene, geranyl acetate, and geranial, as well as nonvolatile compounds, such as pigments, waxes, coumarins and psoralens.

(Table adapted from Calapai, G. et al. Assessment report on Citrus bergamia Risso et Poiteau, aetheroleum. European Union: European Medicines Agency Committee on Herbal Medicinal Products (HMPC). 2012.)

The oil’s composition depends on the method of extraction. Vacuum-distilled bergamot essential oil is psoralen-free, while cold-pressed bergamot oil contains phototoxic psoralens, notably bergapten (5-methoxypsoralen, or 5-MOP) and bergamottin (5-geranyloxypsoralen).^[8][9]

The International Standards Organization (ISO) has established a technical standard for the composition of bergamot essential oil;^[31] however, not all consumer samples of bergamot oil meet that standard.^[32]

There is limited human evidence that bergamot essential oil (BEO) aromatherapy may reduce physiological indicators of stress in already-calm situations, which is consistent with a relaxation-promoting effect, although the evidence for any given indicator is mixed. A 2009 RCT of BEO aromatherapy alone or in combination with soft music, in young adults without any known health conditions, found that soft music, BEO aromatherapy, and the combination of both had positive effects on measures of heart rate variability (HRV).^[5] BEO aromatherapy significantly decreased the ratio of low-frequency variability (LF) to high-frequency variability (HF), indicating increased parasympathetic (“rest and digest”) and decreased sympathetic (“fight or flight”) activity; other studies have observed that this LF:HF ratio increases in stressful situations,^[13] so its reduction is consistent with relaxation. Similarly, although a 2015 study of BEO aromatherapy in women with no known health issues didn’t find a significant effect on HF, it did find a significant reduction in levels of salivary cortisol, which has been linked to stress.^[14]

Several studies have examined the effects of bergamot essential oil (BEO) aromatherapy on stress and anxiety in stressful medical situations, such as hospitalization, waiting in doctors’ offices, during stressful procedures, and presurgery or postsurgery.

There is limited evidence that aromatherapy with bergamot oil may reduce presurgical anxiety in adults awaiting surgery. One randomized controlled trial (RCT) of presurgical anxiety in patients waiting for ambulatory surgery, which exposed participants to either BEO aromatherapy or plain water vapor in the waiting room, found that scores on an anxiety questionnaire decreased more in the BEO group than in the control group.^[15] Similarly, a 2020 RCT in Iran investigated the effects of cold-pressed BEO aromatherapy on participants who were on the point of undergoing gallbladder surgery. The participants who were exposed to BEO had a slightly greater, but still statistically significant, reduction in scores on a standardized anxiety questionnaire and a significantly larger reduction in salivary alpha-amylase (which is correlated with stress) than the participants who weren’t exposed; however, there wasn’t any significant difference in salivary cortisol.^[2] These results are in line with low-quality evidence from a noncontrolled trial which reported that BEO aromatherapy improved positive feelings in the waiting room;^[25] however, that study’s design allowed participants to decide whether or not to participate after exposing them to the aromatherapy, which makes it difficult to give much credence to its results.

The results of a trial examining BEO’s effects on postsurgical anxiety were similar. An RCT whose participants were postsurgical ICU patients found that the participants’ scores on an anxiety questionnaire decreased significantly with bergamot aromatherapy compared to the control group.^[1] However, even though the participants in this small study were randomized, significantly more control-group than bergamot-group participants had had prior ICU experiences, and significantly more bergamot-group patients had a known allergy to something other than plants, flowers and related essential oils — both of which could have affected post-surgical anxiety levels.

However, there is limited evidence that BEO aromatherapy may be ineffective or even counterproductive for medical anxiety in children. A 2019 RCT examining the effects of BEO aromatherapy on medical-office anxiety in autistic children found no significant effect on blood pressure, heart rate, or scores on a standardized anxiety questionnaire.^[3] Worse, a 2012 RCT of BEO aromatherapy in children and adolescents undergoing stem cell transplantation, a stressful, nauseating, and painful procedure, found that the participants who received BEO aromatherapy experienced more anxiety and nausea than the participants who didn’t.^[16]

A few trials have investigated bergamot essential oil (BEO) aromatherapy for job-related stress. However, better-quality studies are needed to be able to draw any conclusions.

A small 2010 randomized controlled trial (RCT) of elementary school teachers in Taiwan compared aromatherapy with BEO to aromatherapy with a synthetic oil with a similar scent. The study found significant pre-post (before-and-after) differences in measures of heart rate variability, a physiological indicator of stress, after natural BEO but not after the synthetic fragrance;^[18] however, since the study’s authors didn’t make any comparisons between the changes seen with natural fragrance and with synthetic fragrance, it’s impossible to say whether the difference between the natural BEO and synthetic control is significant. One additional study in school teachers also found decreases in the physiological markers of work-related stress, such as blood pressure and heart rate, after ten minutes of BEO aromatherapy,^[26] but we can't be sure that these decreases are attributable to BEO because there was no control group.

One further study deserves mention here. Although this study was noncontrolled, it’s of interest because participants were experiencing exceptionally stressful workplace conditions. A noncontrolled, pre-post study of hospital nurses was carried out during the second COVID-19 outbreak in Taiwan (January–April 2021). This study examined the effects of 4 weeks of BEO aromatherapy on both subjective (standardized questionnaires) and objective (physical) measures of the nurses’ stress. While no significant pre-post differences were seen in the objective measures of stress or on the Nurses’ Stress Checklist, the study did note a significant reduction in the nurses’ scores on a standardized burnout questionnaire.^[17] Again, however, this study was not controlled, so it’s impossible to say whether the pre-post differences were due to BEO, especially since it was conducted in the rapidly changing environment of a global emergency.

Although bergamot essential oil (BEO) aromatherapy has exhibited pain-relieving properties in animal studies,^[27] very limited human research has not borne this out to date. One small RCT of 37 children and adolescents undergoing stem cell transplantation, a painful procedure, explored BEO aromatherapy for pain relief and found it had no significant effect on participants’ pain but did result in statistically significant increases in nausea and anxiety.^[16]

Rodent studies of bergamot oil have shown evidence of pain relief and anti-inflammatory efficacy when the oil is applied directly to sore paws.^[9][28] However, while human clinical trials have been planned, no results have been published as of 2024.^[29][30]

A single study provides some indication that bergamot essential oil (BEO) aromatherapy might have positive effects on mood in postpartum women. This four-week RCT of sixty postpartum women in Taiwan, which gave the participants 15 minutes of daily aromatherapy with either BEO or plain water vapor, found that the women who received BEO had significantly lower scores on the Edinburgh Postnatal Depression Scale (EPDS).^[4] However, it’s important to note that the EPDS is not a mood quantifier but a screening scale for peripartum depression; the average scores of all of the groups at all times were lower than the cutoff for possible depression, and the study didn’t report on the number of participants in each group who scored over the cutoff. (Assuming a normal distribution, it can be inferred from the average and standard deviation that many more participants in the control group had scores above the cutoff, but it’s impossible to tell whether this is significant.) So, despite the significant difference in EPDS scores between the BEO and water groups that this study reported, it’s hard to draw any firm conclusions about the effects of BEO on mood in postpartum women or its efficacy for peripartum depression. More research is needed.

There is limited but mixed evidence on the effectiveness of bergamot essential oil (BEO) aromatherapy for sleep quality.

The study of postpartum women in Taiwan discussed in the depression section also measured sleep quality and found no significant difference in postpartum sleep quality between the women who received BEO aromatherapy and those who didn’t.^[4]

However, a 2024 RCT of patients in a surgical intensive care unit found that the participants who received bergamot oil aromatherapy at night, as well as the participants who received lavender oil aromatherapy at night, experienced better sleep quality than the participants who received no aromatherapy.^[1] Similarly, a small 2023 RCT of university students in Japan who inhaled BEO or placebo aromatherapy at bedtime and upon waking for a week found that the participants who had had aromatherapy reported slight but statistically significant improvements in some subitems (sleepiness on rising, feeling refreshed on rising, and duration of sleep) on a standardized scale of sleep quality after using BEO compared to the participants who had had the placebo;^[6] however, no improvement over the placebo was seen in the other subscales, and it’s not clear whether there was any significant difference in scores on the full scale, so it’s difficult to draw a firm conclusion from this study.

In both of the above studies, the aromatherapy was delivered at night, in contrast to the Taiwanese postpartum study, whose participants had 15 minutes of aromatherapy during the day. This suggests that if bergamot aromatherapy does improve sleep quality, the timing may be important. More research is needed.

While bergamot oil has shown antifungal and antibacterial activity in vitro,^[9] human and animal research is lacking.

Bergamot essential oil (BEO) aromatherapy has not been researched as a cancer treatment. It has been investigated as an adjunct to stem cell therapy in children as a possible mitigator for pain, anxiety, and nausea and was found to be worse than no treatment.^[16]

While several individual constituents of BEO have been researched as cancer treatments — for example, bergapten and bergamottin, phototoxic furocoumarins present in small quantities in BEO and in other citrus fruits, have been researched in vitro^[34][35] — there is no evidence supporting the use of BEO as a cancer treatment.

In the past, bergamot oil was included in suntanning products because one of its constituents, the psoralen bergapten, is phototoxic: Skin that has had contact with bergapten may become very photosensitive, rapidly developing dark coloration when exposed to ultraviolet (UV) light. Itching and redness may also develop. The use of psoralens for cosmetic tanning is now understood to be unsafe. Use of bergapten prior to UV exposure can even result in skin-cancer-causing mutations. The use of bergamot oil and bergapten in tanning products was banned in 1995.^[9]

The phototoxicity of the psoralens found in cold-pressed bergamot essential oil, especially the psoralen bergapten, is a drawback in most situations. However, it can be medically useful in the treatment of some skin conditions, including vitiligo, eczema, and psoriasis. For example, people undergoing psoralen and UVA (PUVA) therapy take psoralens orally or apply them topically, then expose skin to UVA light. Cases of second-degree burns due to PUVA therapy have been reported; this therapy should only be done under medical supervision.^[8][33]

Fortunately, when bergamot oil is administered by inhalation, as in aromatherapy, it is has rarely been associated with phototoxicity,^[5] although there has been one case report of blistering when aerosolized aromatherapy in a moist sauna environment was followed by a tanning bed session.^[36] Phototoxicity can be completely avoided by using bergapten-free bergamot oil (BEO-BF) or furanocoumarin-free bergamot oil (BEO-FCF or Bergamot FCF), which can be produced by vacuum distillation or by removal of the bergapten and/or furanocoumarins from the cold-pressed oil.^[8] Vacuum-distilled bergamot oil is bergapten-free.^[37]

There has been one case report of negative side effects from bergamot oil ingested orally. Muscle cramps, muscle twitches, and reduced visual acuity were reported in a man who drank up to 4 liters (about a gallon) of Earl Grey tea, a bergamot-infused tea, each day. His symptoms resolved when he switched to black tea and stayed away as long as he kept his Earl Grey consumption under a liter a day.^[9]

Caution should be used when combining bergamot essential oil (BEO) with photosensitizing medications, such as (but not limited to) carbamazepine. Unless the BEO is furocoumarin-free or bergapten-free (BEO-FCF or BEO-BF), there is a theoretical potential for BEO to increase the risk of photosensitizing side effects.^[38]

It’s worth noting that bergamottin (5-geranyloxypsoralen), a non-phototoxic^[39] furanocoumarin in BEO that is also found in grapefruit and lime juice, is a cyp-450-inhibition|cytochrome P450 inhibitor, particularly of CYP3A4,^[35] and thus could potentially have drug interactions; it is one of the furanocoumarins believed to be responsible for drug interactions with grapefruit juice.^[40] Bergamottin is present at 1.02–2.75% in BEO and at 12–16 ppm in bergapten-free BEO.^[11]

Aromatherapy has effects on the body thanks to multiple methods of delivery. First, in the back of the nasal cavity, olfactory (smell) nerves, which carry over a thousand receptors, detect individual components of the volatile oil;^[14] the olfactory system is connected directly to the limbic system^[23] and to the hypothalamus,^[24] which is involved in control of the autonomic nervous system and is part of the hypothalamic-pituitary-adrenal (HPA) axis, the body’s stress management system. Second, in the lungs, volatile oil molecules can diffuse directly into the body in the capillary blood vessels of the alveoli.^[14] Finally, when volatile essential oils are applied topically, they can diffuse through the skin into subcutaneous tissue, and from there into the blood.^[14]