Ylang-ylang are the aromatic flowers of the cananga tree (Cananga odorata), a plant in the Annonaceae family that is native to Malaysia and Indonesia. Ylang-ylang oil is very widely used as a fragrance in the perfume and cosmetic industries and as a flavoring agent as well.^[2][3][4][5]

In aromatherapy, ylang-ylang oil has been used for reducing fear, nervousness, anxiety, and high blood pressure. It has also been used for improving self-esteem, reducing depression and frustration, and even as an insecticide for mosquitoes and head lice.^{[6][2][7][4][8][9][10]}

Ylang-ylang oil appears to exert a sedative-like effect, compared to a control, in some randomized controlled trials (RCTs), increasing calmness,^[11][12] relaxation,^[12] and skin temperature (potentially indicating a relaxed nervous system),^[12] and decreasing blood pressure^[12][2][13] and heart rate.^[2][13] In accordance with these sedative-like effects, ylang-ylang oil decreased reaction time and how quickly participants were able to recall words in one RCT.^[11] Contrastingly, ylang-ylang oil increased attentiveness and alertness in one trial^[2] but not another one.^[12]

However, in some RCTs^[2][13][14] of ylang-ylang oil, a poor control was used: water. Water is a poor control in this context because it has no smell, meaning the participants might recognize whether they received the active intervention (ylang-ylang oil) or the control (water). This could bias the results in favor of the ylang-ylang oil. A more appropriate control would be something with a smell but no effects on the body (or at least no effects on the outcomes being studied). This might reduce the apparent effectiveness of ylang-ylang oil compared to this aromatic control and potentially give a more accurate representation of its effects.

Despite these aforementioned sedative-like effects, ylang-ylang oil did not reduce anxiety compared to a control in 3 of 4 RCTs.^{[14][1][15][16]} Notably, in the RCT showing a reduction in anxiety, stress, and cortisol,^[16] the intervention group also used lavender and bergamot oil, which also could have reduced these outcomes.^[17][18] This decreases the likelihood that ylang-ylang oil was responsible for the reductions in anxiety, stress, and cortisol.

Furthermore, ylang-ylang oil has not consistently improved other outcomes alongside anxiety, such as cortisol or self-esteem, in RCTs. For example, in one RCT there were no reductions in anxiety or salivary cortisol compared to a placebo.^[14] Similarly, ylang-ylang oil did not improve anxiety in a sample of nurses, though it did improve self-esteem.^[15] However, in an earlier, similar trial by the same authors, ylang-ylang oil did not improve self-esteem.^[6]

Ylang-ylang oil had a sedative-like effect in one randomized controlled trial (RCT), reducing reaction time and the how quickly participants were able to recall words;^[11] however, in contrast, it increased attentiveness and alertness in 1 of 2 other RCTs.^[2][12]

Ylang-ylang oil has been approved for use as a flavoring agent in food by the US Food and Drug Administration and is Generally Recognized As Safe (GRAS) by the Flavor and Extract Manufacturers Association.^[5][7] The quantities used in food are minuscule and may amount to an average consumption of 0.00062 mg per day for the average individual in the US.^[5]

In aromatherapy, where there can be contact with much larger amounts of the essential oil, there have been case reports of people having mild to moderate contact dermatitis (an allergic reaction) on their skin.^[19] It may be an aromatherapy plant with a relatively higher risk of side effects, as a 2012 systematic review of adverse effects of aromatherapy examined 42 case reports and found that ylang-ylang was the 3rd most common plant to have adverse effects (6 case reports).^[19] A 2017 narrative review found that the majority (11 of 13) of the case reports of contact dermatitis from essential oils occurred in occupational exposures by aromatherapists or massage therapists, who can be exposed to large amounts of essential oils over time.^[4]

Ylang-ylang oil has antioxidant, antibacterial, and antifungal properties.^[7][20] It contains a great variety of compounds, such as methyl benzoate (34%), benzyl benzoate (19%), germacrene D (8%–17%), linalool (9%–21%; a main component of lavender oil), caryophyllene (5%; also found in clove oil), and geraniol (5%; also found in citronella oil).^{[21][7][3][4][2][22]}

Because ylang-ylang oil contains linalool (9%–21%, depending on the study^[22][8]), and linalool is a main component of lavender oil (7%–61%, depending on the species of lavender^[23]), it is reasonable to assume it might have some similar effects to lavender, namely improving anxiety, depression, and sleep.^[17][24] However, no evidence was found regarding ylang-ylang oil for depression or sleep, and the RCTs that examined ylang-ylang oil for anxiety found no consistent effects.^{[14][1][15][16]}

It is uncertain how ylang-ylang oil would work to improve anxiety, as one RCT showed no changes in cortisol after overnight aromatherapy with ylang-ylang oil.^[14] Another RCT showed decreased cortisol, stress, and anxiety,^[16] though the participants also used lavender and bergamot oil, which can also reduce anxiety and stress.^[17][18] One rodent study showed that ylang-ylang oil might work to decrease anxiety by increasing levels of a metabolite of serotonin and decreasing dopamine levels; however, this was only found in certain sections of the brain, and only in male rats, greatly reducing our confidence in the generalizability of these results to humans.^[3]