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Follow your nose

Embracing the Benefits of a “Mindful Smell Walk” can Reduce Stress and Boost Your Mood—Here's How It’s Done

ByPhil Green

“The more you immerse yourself in the experience of a scent walk, the more you'll find yourself enjoying the gift of your senses and the world around you."

What is a "smell walk"?

A smell walk is where you mindfully engage with the scents around you. When you focus

your attention to a specific sensory input such as smell, we naturally focus on the present

moment, as opposed to the past or future. We can then detach from our racing, monkey

minds and focus on all the scents around us.

A “Smell Walk” therefore encourages us to slow down and have a slow, patient walk. By

intentionally and mindfully noticing the scents in the air, our focus is naturally taken away

from life's stressors and challenges.

The Smell of the Forest

What is that distinctive aroma when you first walk through woodland? When first entering a forest or woodland, what do you first notice? Is it the cool fresh atmosphere created by the tree canopy or a certain earthy, sweet smell? That smell is


Geosmin, (from the Greek meaning “earth smell”) is formed by microorganisms in the soil.

Geosmin also contributes to Petrichor, the principal component that makes up the aroma of

rain. It is produced alongside spores produced by the bacteria that have accumulated in the

soil during dry weather. Therefore, Geosmin can be sensed within humid air.

So why are we particularly sensitive to the smell of geosmin and petrichor? One possible

explanation is that it is due to some evolutionary psychology perspective. It might have

been a way to detect water sources, or resource-rich ecosystems when traveling across arid

landscapes. What to us is only an invigorating sensory attraction, may once have been vital

to the survival of our ancient ancestors.

Another distinctive forest aroma, especially where there are pine trees is that of

Phytoncides. These Phytoncides are produced by trees as a means protecting themselves

from harmful insects, bacteria and fungi. The word is from the Latin, “Phyton” meaning

plant and “cide”, which means exterminate.

Phytoncides are also part of the communication pathway between trees.

Each tree species produces specific scents, with the evergreens being the largest producers.

These compounds are beneficial to our health. Breathing these in can help in reducing

depression, as well as reducing the levels of stress hormones. They act on the autonomic

nervous system and contribute to the stability of the mind and improving concentration,

focus and mood.

Phytoncides also work as an anti-bacterial system within the body. They have been shown

to kill tumours and virus-infected cells within the body and the impact can last for up to 30

days. Therefore, this self-cleansing process can help boost the immune system.

So, next time you’re mindfully wandering through the woods, remember that scented air

entering your lungs is doing you more good than you may initially have realised.

The Smell of Rain

What’s that distinctive smell of rain after a summer shower and how does it arise?

The smell of rain is known as Petrichor. There are three components that combine to make

up this aroma. These are secretions from soil bacteria, oils secreted by plants and ozone.

A compound produced by soil bacteria is secreted into the surrounding soil. This is known as

Geosmin. When this is disturbed by rain, a distinctive earthy aroma that we can all smell is


When there is a particularly lengthy spell of dry weather, plants can secrete certain oils,

which collect in the rocks and soil. Research has shown that these oils may inhibit growth to

minimise competition for water. After rain, volatile compounds within the oils are released.

Collectively, these compounds together with Geosmin is known as Petrichor.

Experiments have also shown that when a raindrop falls onto a porous surface, small

bubbles are formed by air emanating from the pores. These bubbles float to the surface and

release aerosols. These aerosols that float away carry the odour away in the air, as well as

bringing up bacteria from the soil. More aerosols are formed when raindrops move at a

slower rate. So, petrichor is more noticeable during light rain rather than in heavy storms.

There is another particularly distinctive odour that occurs just before a thunderstorm. When

there is an electrical charge in the atmosphere, ozone is formed by the splitting and

reforming of oxygen molecules. Normally ozone is only found high up in the atmosphere,

where it can’t be detected. However, during a storm, wind downdrafts bring the ozone

further down. That’s when we can smell that ‘pre-rain’ smell.

Each rain event will produce a different distinctive odour. This is because the petrichor,

geosmin and ozone create different mixes in the air.

The Smell of Cold Air

Why does cold air smell different to warm air?

In warm air, odour molecules are more available because they become airborne more

quickly. Therefore, in cold air smells can’t reach our noses as easily. So, our ability to detect

smells is greatly reduced.

Our noses are more attuned to warmer environments. This is because our lungs would be

damaged if our bodies didn’t bring very cold, dry air up to body temperature quickly,

humidifying it in the process. This means that other functions of smell detection won’t be as


Because we are more sensitive to smells in the summer, bad odours will be more


Rain will also make things smell differently too. This is because the odour molecules become

more available and become stuck to surfaces.

With cold air, we may be ‘feeling’ the cold air as well. This is because the Trigeminal nerve in

the nose is triggered. So, the smell of cold air is really a combination of two senses, smell

and feeling.

The Smell of Flowers

Why do flowers smell like anything at all? In order to reproduce and spread their species,

they need strategies to enable them to do this. The production of certain scents can help

solve this problem.

Many plants such as grasses, as well as trees have wind-pollinated flowers so don’t require

smell. Other plants self-pollinate.

So how does one plant get some other individual plant’s pollen where it needs to be? Certain flower species are pollinated by birds, bats, insects or even small rodents carrying

the pollen from one flower to another. These flowers incentivise visits to these flowers by

providing sweet energy and nutrient-rich nectar or protein-packed pollen which they can

eat. Other species are pollinated by insects, and they produce a unique scent to attract the right type of insect.

Flower scents are made up from a large and diverse number of chemicals which evaporate

easily and float through the air. The unique scent of different flower species is due to the type of chemical and its amount, as well as it’s interaction with other chemicals. This is what

gives the flower its unique scent. For example, the scent of a rose may consist of as many as

400 different chemicals.

You can smell these scents because they easily evaporate from the flower, drifting on the air

currents. An apple or cherry tree in bloom emits a sweet scent to attract bumblebees, honeybees and other bees. However, flowers of the pear tree emit a musky or putrid odour. This is to attract flies.

So, when you’re next out for a walk, mindfully smell as many plants as you can and notice

what you can or cannot smell and think what animal or insect might be attracted to it.

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