Bedroom Fragrance: Does a Pillow or a Diffuser Make a Difference?

When you use a fragrance in the bedroom, could the way it reaches you, close to your nose or diffused around the room, matter to how you feel you have slept, as well as the fragrance itself?

In a 2025 study, participants chose a fragrance and delivery method to use at home, and researchers compared their self-reported sleep with records from a wrist-worn device. The diffuser group rated its sleep better than the pillow group, and a specially formulated fragrance differed from the control group on one item assessing sleep quality. However, the study did not demonstrate improvements in device-measured sleep or improvements that persisted after fragrance use stopped.

Studying fragrance and its delivery together

The study aimed to examine how nighttime fragrance exposure at home relates to both subjective sleep and device-based measurements. It focused particularly on the difference between delivering fragrance directly near the nose, using a nose clip or pillow, and distributing it through the room with a diffuser.

The fragrances were lavender essential oil, orange essential oil, and a specially formulated floral-musk fragrance. The formulation combined impressions of citrus, white flowers, rose, jasmine, violet, and musk, with major ingredients including Hedione, musk T, β-ionone, and linalool.

People differ in whether they find the same fragrance pleasant and in the experiences they associate with it. The researchers therefore designed the study so that participants could choose a fragrance they liked.

131 people participated at home for about a month

The participants were 131 healthy adults with a normal sense of smell. Of these, 112 used a fragrance, while 19 formed a control group that used neither fragrance nor a delivery device. Those using fragrance chose both its type and its delivery method.

By fragrance, 37 chose lavender, 37 orange, and 38 the formulated fragrance. By method, 32 chose a nose clip, 41 a pillow, and 39 a diffuser. Rather than trying every option, each participant used one chosen combination.

The nose clip was a small device containing fragrance; the pillow method involved applying fragrance to the pillow before bed; and the diffuser was a container of fragrance solution and reeds placed near the bed. Fragrance intensity was adjusted on the basis of preliminary testing, and different solvents were used for the different delivery methods.

Everyone slept without fragrance for the first two nights to establish a baseline. The fragrance groups then used their chosen method for two weeks, followed by another two weeks without fragrance. This allowed the researchers to examine differences during use and whether any effects persisted afterward.

Questionnaires and wristbands capture different aspects of sleep

Self-reported sleep was assessed using the Pittsburgh Sleep Quality Index (PSQI). This questionnaire brings together sleep quality, time taken to fall asleep, sleep duration, sleep efficiency, sleep disturbances, sleep medication, and daytime dysfunction. Higher scores indicate worse sleep.

It is important to distinguish the total score from the single component asking how people perceived the quality of their sleep. A difference in one component does not necessarily mean there is also a difference in the overall score.

Participants also wore a Fitbit Charge 2 to record total sleep time, time awake during the night, light sleep, deep sleep, and REM sleep. They recorded factors such as coffee and alcohol consumption in a sleep diary.

The analysis compared groups during fragrance use while accounting for differences in their baseline sleep ratings. The researchers also examined changes over time, from baseline to fragrance use and then to the period after use.

The formulated fragrance differed on one sleep-quality component

When the fragrance types were compared, the group that chose the formulated fragrance had better scores than the control group on the PSQI component for subjective sleep quality. This difference was statistically significant after adjustment for baseline ratings.

There were no significant differences by fragrance type in the total PSQI score or its other components. Neither lavender nor orange produced a clear result showing better sleep than the control condition.

The direct finding is therefore a difference in one aspect of subjective sleep quality in the group that chose the formulated fragrance. This comparison could not establish whether the blend worked because it contained several fragrances, or whether liking and relaxation were involved.

Delivery method: a difference between diffuser and pillow

When delivery methods were compared, the diffuser group had a lower, and therefore better, total PSQI score than the pillow group. This difference was also present in the analysis adjusted for baseline scores.

However, the results cannot readily be summarized as showing that a diffuser broadly improved sleep compared with no fragrance. For subjective sleep quality, the pairwise comparison between diffuser and control was near the significance threshold, but the overall test of delivery method did not reach significance. The difference from control in daytime fatigue was also not significant, amounting only to a trend in a favorable direction.

A separate model examining changes over time also found a difference between diffuser and pillow during use. However, the interaction testing whether change over time differed by delivery method narrowly missed the significance threshold. In the pairwise comparisons from this model, the pillow group’s total score was higher, indicating worse sleep, both during and after use than at baseline.

These results suggest that fragrance placement may relate to personal comfort and sleep ratings. At the same time, it is important to distinguish a difference relative to the pillow method from a difference relative to a control group using no fragrance.

What did the device records and post-use period show?

In the baseline-adjusted Fitbit comparisons, there were no significant differences in sleep measures by fragrance type or delivery method. The findings did not support interpreting the subjective differences as improvements in sleep duration or sleep stages.

In the model that included time, the lavender group had longer light-sleep duration than the orange group. However, that between-group difference is not the same as a comparison showing improvement after introducing fragrance. Longer light sleep also cannot simply be equated with better sleep quality.

No improvement persisting after fragrance use stopped was demonstrated. Nor was there a clear change in odor-detection sensitivity measured before and after the study.

Before interpreting differences between chosen methods as causal

A distinctive feature of this study is that participants chose both the fragrance and its delivery method. Although this resembles everyday use, the groups were not randomly assigned. Expectations about fragrance, lifestyle, and reasons for choosing a method could have contributed to differences in sleep ratings.

The subgroups combining fragrance and delivery method were also small, and the control group contained 19 people. Fitbit cannot capture changes in as much detail as a sleep examination using brain-wave recordings, so there is no single established explanation for the absence of device-measured differences.

The participants were healthy adults; this was not a treatment trial for diagnosed insomnia. The study’s value lies in showing why bedroom-fragrance research needs to consider delivery method as well as fragrance type, and both subjective and device-based outcomes.

Summary

In this home-use study of preferred fragrances, the formulated-fragrance group had a better score than control on one component, subjective sleep quality. The diffuser group had a lower, better total sleep-questionnaire score than the pillow group, although the pillow group itself worsened relative to baseline. How a fragrance is delivered, as well as what it smells like, may relate to how people experience their sleep.

The study did not demonstrate device-measured improvements or improvements lasting beyond the period of use, and participants chose their own methods. When considering fragrance and sleep, it is important to examine both feeling that one slept well and sleep as measured by a device.

The paper reports support from Takasago Europe and Volkswagenstiftung. The coauthors included a researcher affiliated with Takasago Europe at the time of publication, and Thomas Hummel disclosed collaborations with several companies.

Reference

Li Z, et al. (2025). Effects of nighttime odor exposure and delivery methods on subjective sleep quality in healthy adults. Scientific Reports, 15, 32452. Original paper / Open full text