• Macs

Smell And Sleep: Can Smells Affect Us During Sleep?

Updated: Aug 1, 2018

Smell is the most sensitive of our 5 senses. Our brains can process about 1 trillion different stimuli from an area the size of a 2p piece. So have you ever wondered what happens to our sense of smell once we fall asleep? In this post I explore just how active our sense of smell is during our slumber and the extent to which it influences the quality of our sleep.

Smell and Sleep quality image

Can a strong smell wake you?

In 1997 the Irondale Fire and Rescue Service in Alabama conducted a small study involving 10 participants to ascertain whether the smell of smoke could awaken a sleeping person. Only two out of ten adults in the test group woke up, promoting their conclusion that smoke alarms are essential. The fact that at least 80% of people cannot rely on their sense of smell to alert them to the danger of fire may explain why more than half of all American home fire deaths occur at night.

To put it plainly, when you are asleep your olfactory awareness (smell processes) is lowered to the point where your sense of smell becomes almost non-existent. According to experiments by Brown University professor of psychiatry, Rachel Herz, people did not respond to odours while they were in the dreaming phase of sleep (REM) or deep sleep. “You cannot smell while you are asleep,” she said. “You don't smell the coffee and wake up; rather you wake up and then smell the coffee.”

Our sense of smell is actually a key demarkation between being awake and being asleep.

However, this is not to say that smells don't play an important part in our quality of sleep. So how can this be? Our sense of smell is actually the sense most linked to our emotional recollection, in turn strongly affecting moods and even concentration. This vital connection to memory means people can recall smells with 65% accuracy after a year, while visual recollection is about 50% after three months. Shrewd marketing and experiential experts know all to well the power that the right scent can have on our emotions – remember the strong aroma of freshly brewed coffee the last time you walked through the entrance of Waitrose? At least 75% of all emotions generated every day are due to smell, and because of this, we are 100 times more likely to remember something we smell over something we see, hear or touch. Research shows that there is even a 40% improvement in mood after being exposed to scents we consider to be pleasant.

It seems women are most susceptible to being influenced by this particular sense, since their sense of smell is stronger than men's. A study by scientists at the Federal University of Rio de Janeiro in Brazil found that women's brains had on average up to 50% more olfactory neurons than men. There are numerous theories as to why the sexes differ, but many believe it is due to cognitive and emotional influences rather than perceptual ability. A superior sense of smell may help a mother and child to bond after birth and possibly to influence a females' selection of potential mates.

With such a strong connection to emotion and memory the potential of using smell to influence our mood and therefore our sleep is enormous. And the internet is full of suggested scents that can ease you gently into the land of nod. None more popular than lavender.

Lavender has long been considered an effective aromatic sleep inducer.

In 2015, Turkish experts conducted a study with 60 patients in a coronary intensive care unit, where sleeping was difficult due to the 24 hour activity of the medical staff. Patients who inhaled lavender aromas for two weeks reported less anxiety and higher quality sleep. Science writer, Luis Villazon, says that this particular smell may not just be soporific due to the fact it 'reminds you of the comforting smell of your granny’s house'. Lavender oil is mainly composed of the chemicals linalyl acetate and linalool that can be rapidly absorbed into the bloodstream. In studies on mice these compounds have been shown to inhibit several neurotransmitters and have a sedative and pain-relieving effect. The scientific evidence that lavender may slow the activity of the nervous system and improve a persons quality of sleep continues to grow.

But for the majority of scents, the therapeutic qualities of some smells generally have less to do with their latent power over the brain, and more to do with our own associations. Smells considered to be most relaxing are those often associated with massages, fresh sheets and scented bath oils such as ylang ylang and vanilla. These powerful associations can decrease heart rate and blood pressure and put you in a more relaxed state of mind. If integrated as part of a nightly sleep routine then undoubtedly our brains learn to link certain odours with sleep. Taking your sense of smell in to consideration when thinking about sleep is a wonderfully inexpensive and simple way to ease yourself into a deep and uninterrupted night of blissful slumber.

Are there any scents you find particularly relaxing? Do you associate them with certain experiences? Have you encorporated aromatherapy into your sleep routine? Let us know in the comments section below:


 Welcome to Sensorama - a blog to tickle the senses.


This blog is dedicated to curiously exploring the world via the 5 senses of sight, sound, smell, taste and touch.
Our perception of reality is determined by our own senses - and there are millions of sensory experiences out there for us to explore. Join sensorama bloggers Macs and Oliver as we take you on an extraordinary tour of the world all around us through sensory science, experiences, stories and sensations.


Via Sight : Beautiful faces, amazing colours, hidden lights spectrums, optical illusions, incredible animals and emotive art - our ability to see is central to nearly every part of our everyday lives. Yet how often do we stop and take a fresh look at the world? At Sensorama we take a second glance at the everyday, the unusual and the at times invisible.

Via Sound : Hearing is the key to communication and how we interact. Like a heartbeat, it is also highly personal. From thrash metal to choral hymns which make the heart soar - what we love to listen to can determine our mood, emotional state, and sense of identity. At Sensorama we take a in depth listen to the beats of life.  

Via Smell : Smell is the sense that much of the animal kingdom relies on to find food, sense danger or attract a mate. It is the sense which can evoke a long distant memory and silently affect our perceptions and behaviours. At Sensorama we pay attention to what’s right under our nose.  

Via Taste : What some cultures find delicious, others find repulsive. Taste is so often a matter of, well, taste. Starting as an evolutionary way to avoid poisoning, we have mastered the sense of taste to tickle some of the strongest pleasure centres of our brains. At Sensorama we search out the tantalizing and delicious.


Via Touch : Touch can be anything from comforting to terrifying and take us anywhere from excruciating pain to heightened ecstasy. As humans, we feel everything but so rarely pay attention to what our bodies are telling us. At Sensorama we get hands on with all the textures of the world.

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