Can a Sweet Smell Help Premature Babies Breathe More Steadily?

What a Swiss study of vanilla and strawberry scent in babies' breathing masks (Gähwiler et al., Pediatric Research, 2026) and other new research tell families about smell and breathing pauses

Many babies born very early have short pauses in their breathing that can make their oxygen level and heart rate dip. Researchers in Zurich, Switzerland, tested whether a pleasant vanilla or strawberry smell placed inside the small mask that helps these babies breathe could reduce those episodes. In 80 babies the scent caused no harms the researchers could find but made no clear difference, possibly because the steady airflow through the mask diluted it.

If your baby was born very early, you may have watched the monitor beside the incubator chime because their breathing paused or their heart slowed for a few seconds. This is common, it usually settles as babies grow, and the care team is well practiced at handling it. This article explains a new study that asked whether a gentle, drug-free idea, a pleasant smell, could help [1], and how it fits with a French study [2] and a large review of earlier research published the same year [3].

Why very premature babies sometimes pause their breathing

The part of the brain that controls breathing is still maturing in babies born early. As a result, they can stop breathing for a short time, a pattern called apnea of prematurity. It is one of the most common conditions in the neonatal intensive care unit (NICU), the hospital unit that cares for sick and premature newborns [4]. These pauses often come with a drop in oxygen in the blood (called a desaturation) or a slowing of the heart (called bradycardia). Such episodes tend to become more frequent over the first four weeks of life and then slowly settle [5].

Doctors take these episodes seriously. Some studies have found that babies who had many long episodes, especially ones lasting a minute or more, were more likely to have later health or developmental problems [6][7]. These studies show a link, not proof that the episodes cause the problems, and experts still do not know for certain whether the episodes are harmful in themselves [4]. Still, it makes sense to reduce them where it can be done safely.

How breathing pauses have been treated until now

For many years, two treatments have done most of the work. The first is caffeine, the same substance found in coffee, given in carefully measured doses. A very large study of 2006 small premature babies found that caffeine helped them, for example by reducing how many still needed extra oxygen later on [8]. The second is CPAP (continuous positive airway pressure), a gentle, steady flow of air through a small mask or soft tubes at the nose that helps keep the airway open. It is widely used, although studies comparing different CPAP devices are few [9]. Laying babies in certain positions can also help [10].

Even with these treatments, many babies still have episodes, and nurses often respond by gently touching or rubbing the baby to remind them to breathe [11]. Medicines for breathing pauses, especially stronger ones, can cause side effects such as irritability, poor sleep and a fast heart rate [12]. You can read more about these options in our article on treating breathing pauses beyond caffeine. This is why researchers have looked for gentle, drug-free ways to help.

Where the idea of using smells came from

Researchers have long wondered whether a pleasant smell might gently nudge a premature baby's breathing. In 2005, a study of 14 very premature babies who kept having pauses despite medicine placed a pleasant smell in their incubators for 24 hours. The babies had about a third fewer pauses (36% fewer) than on the days before and after, with no side effects [13]. A later study in Turkey, which put a piece of gauze soaked in vanilla in the incubator, also reported fewer pauses [14]. But a more careful study in Canada of 27 babies found that vanilla made no clear difference overall [15]. Other researchers have used the smell of the mother's breast milk, mainly to help with feeding and to keep babies' heart rate and breathing steady [16][17].

There was an important gap. None of these earlier studies included babies on CPAP, even though CPAP is now the usual treatment for babies with frequent pauses. When a mask covers the baby's nose, a scented cloth near the face probably cannot reach them [1].

How the Zurich study worked

The study took place at the University Hospital Zurich, Switzerland, between June 2023 and January 2025 [1]. It included babies born between 23 and 31 weeks of pregnancy (babies are considered premature when born before 37 weeks [3]) who were more than three days old, on CPAP and already receiving caffeine. Parents gave written consent. The typical baby was born at just over 27 weeks and weighed a little under one kilogram.

Each baby took part on two nights. On one night, a nurse used a special pen, made for scenting children's masks during anesthesia, to draw three circles of vanilla or strawberry scent inside the baby's CPAP mask, topping it up every three to four hours. On the other night, the nurse used a pen that looked exactly the same but had no smell. This type of study is called a cross-over trial: each baby tries both options, so each baby is compared with themselves. The order was decided by chance, and neither the parents, nurses nor researchers knew which pen was which. Each period lasted 12 hours, with a 12-hour break in between. Monitors automatically counted every time the baby's oxygen fell below 80% or the heart rate fell below 80 beats per minute for more than 10 seconds.

What the researchers found

Eighty babies completed the study. During each 12-hour night, a typical baby had about 10 episodes with the scent and about 14 without it. Those are middle values (medians), and numbers varied widely from baby to baby. This gap was small enough that it could easily have happened by chance, so the researchers concluded the smell made no measurable difference [1]. Looking at individual babies, 42 of the 80 had fewer episodes on the scented night, while 32 had more. Vanilla and strawberry gave the same result. Oxygen needs, feeding and the other measurements did not change, and the time babies spent with low oxygen was similar on both nights (a median of 9 minutes with the scent and 11 minutes without).

It can be disappointing when a hopeful idea does not work out, but a clear answer like this is valuable. It spares babies an extra treatment that does not help and lets researchers focus their energy on better ideas.

There was good news on safety. The researchers found no harms caused by the scent, no baby's feeds had to be stopped, and no baby needed a step up in breathing support for more than half a minute during the study. One baby left the study because of a neck infection that needed a breathing machine and antibiotics.

Why the smell may not have reached the baby

The researchers' main explanation is the delivery method. CPAP blows a constant stream of air through the mask, which may have diluted the scent until it was too faint to notice. Nobody measured how much scent actually reached the baby's nose. Another possibility is that caffeine and CPAP were already working so well that there was little room left for a smell to help. The authors stress that their result applies to this pen-in-the-mask method, not to smell as an idea in general [1].

What other new research says

A second study, the PREMODEUR trial (automatic, on-and-off scent delivery), led from the Hospices Civils de Lyon in France, used a machine to send short puffs of mint, grapefruit and vanilla scent to 15 premature babies who had frequent pauses [2][12]. Its main result also showed no clear difference compared with puffs of unscented air. No harms were seen with the system, and the researchers said a small benefit could not be ruled out because the study was small [2].

A large review from Cochrane, an organization that gathers and weighs all the research on a question, looked at 14 studies of smell in 1087 premature babies [3]. It found that food smells such as vanilla might slightly reduce breathing pauses, but this was based on only two small studies and the evidence was weak. The review was finished before the Zurich and French studies were published, so they are not yet included.

What this means for your baby

For babies on CPAP and caffeine, putting a scent into the breathing mask does not appear to help with breathing pauses, so your care team is unlikely to suggest it. Please do not add scents, oils or perfumed items to your baby's mask, tubing or incubator yourself: the right amount is unknown, and only specially made products were tested. Caffeine, CPAP and careful positioning remain the treatments with the strongest evidence [10]. Breathing pauses usually become less frequent as babies mature [5], and your baby's team can explain how they are tracking your baby's episodes and what they mean.

What researchers are working on next

The Zurich team hopes future studies will measure how much scent actually reaches a baby's nose and design delivery systems that work with CPAP [1]. Other experts have called for automatic systems that gently stimulate babies on breathing support when a pause begins [11]. The Cochrane review found five studies still under way [3]. For now, smell remains an interesting idea that has not yet been shown to help babies on breathing support, and families can feel reassured that the proven treatments their baby receives are doing the most important work.

References

  1. Gähwiler K, Rüegger CM, Dirler C, et al. The effect of nasal olfactory stimulation on apnea of prematurity: a randomized cross-over trial. Pediatr Res. 2026. doi:10.1038/s41390-026-05285-w ↩
  2. Gauthier-Moulinier H, Nguyen HKA, Fischer C, et al. Automated intermittent olfactory stimulation to reduce apnea in preterm infants: results of the PREMODEUR randomized clinical trial. Eur J Pediatr. 2026;185(9):654. doi:10.1007/s00431-026-07318-2 ↩
  3. Lenells M, Prescott MG, Wróblewska-Seniuk K, Fiander M, Soll RF, Bruschettini M. Olfactory stimulation for promoting development and preventing morbidity in preterm infants. Cochrane Database Syst Rev. 2026;5(5):CD016074. doi:10.1002/14651858.CD016074.pub2 ↩
  4. Eichenwald EC. Apnea of Prematurity. Pediatrics. 2016;137(1):e20153757. doi:10.1542/peds.2015-3757 ↩
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  7. Janvier A, Khairy M, Kokkotis A, Cormier C, Messmer D, Barrington KJ. Apnea is associated with neurodevelopmental impairment in very low birth weight infants. J Perinatol. 2004;24(12):763-768. doi:10.1038/sj.jp.7211182 ↩
  8. Schmidt B, Roberts RS, Davis P, et al. Caffeine therapy for apnea of prematurity. N Engl J Med. 2006;354(20):2112-2121. doi:10.1056/NEJMoa054065 ↩
  9. Ho JJ, Zakarija-Grkovic I, Lok JW, Lim E, Subramaniam P, Leong JJ. Continuous positive airway pressure (CPAP) for apnoea of prematurity. Cochrane Database Syst Rev. 2023;7(7):CD013660. doi:10.1002/14651858.CD013660.pub2 ↩
  10. Poets CF. Interventions for apnoea of prematurity: a personal view. Acta Paediatr. 2010;99(2):172-177. doi:10.1111/j.1651-2227.2009.01604.x ↩
  11. Lim K, Cramer SJE, Te Pas AB, Gale TJ, Dargaville PA. Sensory stimulation for apnoea mitigation in preterm infants. Pediatr Res. 2022;92(3):637-646. doi:10.1038/s41390-021-01828-5 ↩
  12. Duchamp-Viret P, Nguyen HK, Maucort-Boulch D, et al. Protocol of controlled odorant stimulation for reducing apnoeic episodes in premature newborns: a randomised open-label Latin-square study with independent evaluation of the main endpoint (PREMODEUR). BMJ Open. 2021;11(9):e047141. doi:10.1136/bmjopen-2020-047141 ↩
  13. Marlier L, Gaugler C, Messer J. Olfactory stimulation prevents apnea in premature newborns. Pediatrics. 2005;115(1):83-88. doi:10.1542/peds.2004-0865 ↩
  14. Kanbur BN, Balci S. Impact of the odors of vanilla extract and breast milk on the frequency of apnea in preterm neonates. Jpn J Nurs Sci. 2020;17(1):e12271. doi:10.1111/jjns.12271 ↩
  15. Bergeron S, Champoux-Ouellet É, Samson N, et al. Effects of vanilla odor on hypoxia-related periodic breathing in premature newborns: A pilot study. Arch Pediatr. 2024;31(6):369-373. doi:10.1016/j.arcped.2024.03.002 ↩
  16. Yu L, Tao Y, Jia P, et al. Effect of breast milk olfactory experience on physiological indicators in very low birth weight infants: a randomized clinical trial. Sci Rep. 2025;15(1):20590. doi:10.1038/s41598-025-05809-0 ↩
  17. Muelbert M, Lin L, Bloomfield FH, Harding JE. Exposure to the smell and taste of milk to accelerate feeding in preterm infants. Cochrane Database Syst Rev. 2019;7(7):CD013038. doi:10.1002/14651858.CD013038.pub2 ↩