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The Power of the Fragrance What do we know about our olfactory sense?

Editor: Dipl.-Chem. Marc Platthaus

Inhaling, smelling, sniffing – the human nose is capable of detecting the most diverse aromas. However, the act of smelling encompasses more than the simple scent. If something bothers us, “it stinks”. How are our actions influenced by what lies in the air?

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Humans posses about 10 million olfactory cells. How do they work?
Humans posses about 10 million olfactory cells. How do they work?
(Source: © Khorzhevska /

On average, an adult will inhale and exhale 26,000 times per day. Despite the millions of scent molecules entering our nose, humans are capable of detecting and distinguishing only about 10,000 of the 400,000 scents existing on earth. At the same time, these must be highly concentrated. This makes us humans rather poor smellers — microsmatic. In comparison, the mucus membrane of our nose covers only one fifth of that of a cat, and whereas dogs possess approximately 240 million olfactory cells, humans must make do with only about 10 million. All these insights do not change the fact that science knows considerably more about the other four sensory organs than it does about the olfactory sense. The visual sense depends on the wavelength of the light, and the auditory sense detects frequencies and amplitudes.

The factors which make a difference during the act of smelling are not easily discerned. This is why, when we describe a scent, we refer to the other senses. A fragrance is therefore heavy or floral, or it is circumscribed using comparisons such as “smells of freshly mown grass”. Researchers are nevertheless certain: our olfactory sense and what it perceives exerts a vast influence on our daily lives — conscious as well as unconscious.

For example, certain emotions may be elicited if they are connected to a scent — a fact which has been known since antiquity. The Greek philosopher Aristotle knew: “Man does not perceive a fragrance without experiencing a sense of either pleasure or displeasure.”

Our sense of comfort also depends on what we smell. Even our mood and our actions can be manipulated or even directed by fragrances. Industry in particular has discovered this power of manipulation called scent branding. For the past few years, supermarkets have been enveloped in the aroma of freshly baked bread, and movie theaters smell of popcorn where there is none.

Scent makes you feel comfortable and at home

All these manipulations have the same goal: to prompt impulse purchases that the visitor may not have considered in the absence of surround smell. Or they are supposed to feel so comfortable that they will always return. An American hotel chain sprays their lobbies with the scent of apple pie so that guests will feel at home immediately.

They are taking advantage of the fact that the olfactory bulb is integrated in the limbic system, the very region of the brain which is responsible for processing emotions. This is why scents will typically elicit an instinctual response and only rarely a rational one. Olfactory perception is passed directly from the hippocampus to long term memory storage, without being filtered.

For this reason, scents are closely linked to memories. When we inhale certain fragrances, images, emotions and even physical reactions often appear instinctively.

Surrounded by the smell of freshly baked cookies, we think of Christmas. If a person ahead of us on the street wears a perfume that reminds us of a familiar person, that person will appear before our mind’s eye.

This also works the other way around. Looking at a photograph from our childhood, at times the very smell that our memory associates with the event will enter our noses — although it is not present at the time.

There are different olfactory triggers

Every person has their very own olfactory memory triggers. The important difference is whether the salty smell of the ocean or the warm summer rain is linked to positive or negative memories.

Our olfactory sense not only influences our purchasing decisions and our memories. Love, too, goes through the nose. “Whoever controlled the fragrances controlled the hearts of men”, says Jean-Baptiste Grenouille, the perfumer with the distinct ability to discern fragrances, in Patrick Süskind’s 1985 bestseller “Perfume”.

We are under the impression that when it comes to the choice of a partner, external factors decide whether or not we will find someone attractive. However, it is finally the nose which guides us. Especially men and women with distinct aromas will find each other interesting. The fragrance of the body represents an expression of our immune system.

This is the reason our olfactory system prefers those potential partners whose bodily scent — and therefore whose immune system — is as different from our own as possible. Such a union will produce offspring who are equipped with an ideal and especially robust combination of both immune systems — an evolutionary mission which should not be underestimated.

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There are, however, influential factors which may change olfactory preferences: the contraceptive pill, but also age and past experiences influence our reactions to scents. Even if the aroma may be the initial trigger — once we get to know a person more closely, all the senses will have their say. map

Note: This article was first published in the Eppendorf magazine “Off the Bench” in December 2016.