Global sales of perfumery products are estimated to reach 40.4 billion USD by 2022. It is clear that perfume is a desirable attribute of modern society – unusually immaterial, difficult to perceive, ephemeral... Why is pampering the sense of smell so important today, yesterday and far back in time? What profound effects do aromas have on the human body?

Rachel Herz, Ph.D. at Brown University, an expert in the psychology of fragrances identifies the sense of smell as one of the essential conditions for survival and existence of a living organism. In the book "The Scent of Desire: Discovering Our Enigmatic Sense of Smell", the scientist writes: "The sense of smell has evolved from a simple survival function to a very complex system that tells us to go or not, helps to find food or a mate, to create social hierarchies, to judge whether to be aggressive or fearful to avoid predators, and is useful in many other difficult situations. The sense of smell is the main sense that most animals rely on to navigate the world." The scientist explains that positive emotions caused by an acceptable smell encourage to approach, push forward, ensure reproduction and survival. Therefore, for humans, the emotions evoked by smell have become the same approach or avoidance codes that the smell sends to animals. According to R. Herz, the human ability to experience and express emotions evolved from the brain's ability to process smell. "I smell, therefore I feel," sums up the expert in the psychology of smells.

Deep into aromatherapy

The history of perfumery tells us that since ancient times, not only ritual, but also therapeutic, healing powers of aromas have been believed. Marie-Christine Grasse, Chief Curator of the Museums of the City of Grasse, in her book "Perfume, a Global History: from the Origins to Today" states that "perfume is a product endowed with therapeutic, aesthetic and ritual values. /.../ It evokes the memory, stirs the senses and opens the wearer to the world.” It is noted that perfume first appeared in ancient Mesopotamian written documents in the middle of the third millennium BC in the form of scented oils used by living people to anoint their bodies. Many ancient civilizations – Egypt, China and India – have used aromatherapy for thousands of years for healing and wellness purposes, seeking positive spiritual, mental, physical effects. Fragrant plant compounds are used to alleviate various mental and physical disorders: relieve headaches or other pains, treat eczema, insomnia, digestive ailments. Thus, the concept of aromatherapy originates from ancient cultures that believed in the healing properties of plants.

However, even today, aromatherapists believe, and some scientific research substantiates, that the stimulation of the sense of smell with certain scents has various psychophysiological effects on the human body. After studying medicinal, aromatic plants (for example, lavender (perhaps the plant that has received the most scientific attention), bergamot, cumin, eucalyptus, geranium, juniper, lemongrass, mint, peppermint, pine, rosemary, sage, tea tree, thyme, etc.) it was discovered that they contain not only aromatic, but also bioactive components that affect the body's chemical processes, can change the mood, and in the case of various diseases – accelerate healing.

Do we really smell with our nose?

Based on the data of today's flourishing perfumery industry, it is assumed that today's perfume has become one of the forms of stimulation of dopamine – the pleasure hormone. How is it possible? As we delve deeper into the activity of the olfactory system, we will realize that smell affects the brain through the sense of smell. The olfactory mucosa is the area at the top and back of the nasal cavity that is dedicated to detecting odorous molecules. The olfactory receptor cells contain fibres where the molecular reception of odours takes place. Information through the sense of smell is transmitted directly to the amygdala, where the interpretation and response of the sense of smell takes place. Olfactory sensory neurons send electrical signals to the brain. The olfactory system is characterized by direct connections with brain structures related to memory and emotion. Therefore, studies have shown that the effects of various scents on mood, physiology and behaviour are due to the direct ability of scent to affect the central nervous system. This substantiates why scents have a profound effect on various mental and physical human states. Therefore, to say that we smell with our nose would not be quite correct: with our nose we only inhale and direct the air full of odorous molecules; we "smell" the smell with nerve cells, and perceive it with the brain.

Smell psychologist R. Helz has an even deeper explanation in the context of neuroscience: "The neurological connection between the sense of smell (olfaction) and emotions is extremely close. The areas of the brain responsible for smell and emotion are closely connected and interdependent. Smell and emotion are located in the same network of neural structures called the limbic system. The main limbic structure that interacts with our olfactory centre is the amygdala. The amygdala is the seat of emotions in the brain. /…/ Brain imaging studies show that smelling activates the amygdala, and the more emotional the response to the smell, the more active it is. No other sensory system has such exclusive direct access to the part of the brain that controls our emotions."

The scientific geometry of smell

R. Helz scientifically describes the smells as complex chemical substances consisting of thousands of different molecules, for example, the smell of roses consists of 1200-1500. "For a person to be able to smell a chemical substance, it must be of low molecular weight, volatile, water-resistant, which allows it to stick to the olfactory receptors. /.../ With each inhalation, the odour molecules in the air enter the nostrils and are then directed upwards into the nasal passages. /.../ Olfactory receptors are located in two areas of the yellow mucous membrane – the olfactory epithelium, located approximately 7 cm above each nostril. Olfactory receptors are located at the ends of dendrites of olfactory neurons. We have about 20 million olfactory receptors. /…/ compared to 220 million olfactory receptors that a dog has."

An attempt was made to objectify by electrophysiological studies the complex process of smell perception and its effect on brain activity described in this way. They found that different smells evoke spontaneous brain activity and cognitive functions, which are measured by an electroencephalograph (EEG). Some aromas have been tested with this device from different angles with different groups of people (see the table).  

Psychological effect – placebo effect?  

Experts do not fully understand how aromatherapy works. However, some studies illustrate that aromatherapy may have benefits in the treatment of severe mental illness. Research has shown that chemicals in essential oils can activate the smell receptors in the nose, which send messages to the part of the brain that controls a person's mood. Although there is ongoing active work in this area, more detailed research is needed to summarize whether aromatherapy can help treat illnesses like depression.

The neurological effect of smell was explained as early as the 1 century by Dejean, based on the fact that the nose is close to the brain. According to the researcher, "what is sensitive to the nose consists of volatile, subtle, penetrating parts that not only touch the olfactory nerve, but also spread throughout the brain." Dejean wrote that “the power of scents is directly related to the instinctive and primal relationships they evoke; throughout the ages they were believed to bring death, pleasure or displeasure.' Such a historical hypothesis and a picturesque metaphor are rationalized by modern science and medicine. Researchers of the nervous system say that the loss of the sense of smell can lead to the development of chronic mental illnesses. American neuroscientist John McGann believes that doctors should pay much more attention to the treatment of olfactory disorders. According to him, some studies show that the loss of smell can affect memory disorders and cause Alzheimer's and Parkinson's diseases; therefore, it is very important that the medical world pays as much attention to the research of the olfactory system as possible.

Many scientists argue that the most significant information of smells is basically not consciously perceived; therefore, if you have a weak sense of smell, it does not mean that you do not distinguish smells. However, if the olfactory system has serious disorders (especially in children), it interferes with the perception of the sense of reality, which can lead to the development of mental retardation and lack of imagination. Therefore, the importance of training and stimulation of the sense of smell for the activation of brain activity is emphasized. For example, a famous study was conducted in the USA, during which students were given to smell a cinnamon stick every day. After a while, it was noticed that the observation participants coped much better with mental tasks. Meanwhile, Japanese researchers noticed that people who went for a daily walk in a conifer forest were in a much higher mood. The popular conclusion is that the smell of conifers reduces stress. That's why people are in a higher mood before Christmas, they feel happier...

‍Psychophysiological effect of a smell

There are about 300 active olfactory receptors in the human body that are designed to detect thousands of different molecules  of odorous materials. Many studies prove that the sense of smell plays an important role in the physiological effects of mood, stress and performance. The olfactory system plays a key role in the functions of the central nervous system; therefore, its stimuli have a strong physiological effect. This is the basis for the effectiveness of aromatherapy on the human body and the assumption that a certain essence can help reduce blood pressure, calm down, improve sleep quality, work capacity, provide energy, and relieve nausea. In addition, studies have shown that long-term inhalation of odors affects the parameters of the autonomic nervous system and the state of the brain.                

According to R. Herz, "there is no scientific research that after inhaling the aroma of white sandalwood, its essence is detected in the blood circulation. Thus, the smell directly affects the psychology, and through it has a physiological effect. The author of the book “The Scent of Desire” states that "the emotional association of lavender is relaxation, and we’ve 'learned' it in the same way we’ve learned that roses smell and skunks stink." A learned association can have real emotional and physical consequences, which in turn influence mood, thoughts, behaviour and general well-being." According to the researcher, cultural learning can influence a specific emotional reaction to smells. Aromas change mood, calm or excite because of previously formed emotional associations, not because of their inherent narcotic effects. The joy of aromatherapy is in the mind of the smeller, and is not caused by the effect of the aroma, but by the person's secondary associations and emotions with that smell. Through associations, smells can be turned into emotions, and then the emotions themselves can be changed: influencing feelings, thinking and actions. The smell was said to stimulate the same behaviour that was characteristic of experiencing that emotion. Thus, positive odour associations can have a positive emotional effect, or vice versa. "Associating the feeling of intellectual competence with a specific smell /…/ may increase the productivity of people who are willing to study or work. The correlation between smells and emotions can be applied to improve social behaviour in a stressful environment," R. Herz summarizes in a study of the psychology of smells.                

The positive effects of aromas are not limited to mood; physical states can be influenced as well. Fragrances that people like are mood-enhancing and positive, while those that are disliked tend to be mood-depressing and have a negative or neutral effect. According to the scientist, scents can probably be used effectively in psychotherapy to help people overcome anxiety. For example, a scent associated with calm can help an anxious person relax. It should be noted that the smell will be calming if it has positive associations for the person who smells it. Associations between emotions and smells depend on personal experience and can be unpredictable. If the smell of the sea calms some, it can trigger a post-traumatic stress attack in tsunami survivors.          

Smell is a condition for optimism              

We have already emphasized that, according to science, smell is a direct and one of the most accurate guides of living organisms towards survival, well-being, and pleasure. A well-functioning olfactory system greatly enriches a person's life and ensures an excellent emotional state (we have already discussed that in the case of us, humans, the original olfactory code has turned into emotions; therefore, the sense of smell and emotional experience are basically connected). Therefore, the loss of the sense of smell - anosmia - can plunge a person's mental system into a devastating emotional abyss. And damage or loss of the olfactory system is quite simple. The probability of injury is illustrated by R. Helz: "The part of the brain, specifically the area responsible for the sense of smell – the olfactory bulb and the olfactory cortex. Neurons in the nose are separated from the olfactory bulb in the brain by a very thin and fragile bone called the lamina plate. This plate contains thousands of tiny angels through which the ends of olfactory receptor neurons (called axons) enter the brain. A hard impact to the front of the head dislodges the lamina plate, cutting off the delicate olfactory receptors axons that pass through it. /…/ When the axons are interrupted, the olfactory nerve dies and the sense of smell is lost forever. Many frontal head injuries can result in loss of smell.”    

In her book, the olfactory psychologist tells how a famous music artist who had gourmand tendencies, lost his sense of smell in an accident; as a result of which he began to sink into depression and committed suicide. "Patients who have experienced an anosmia – caused by a head injury – often report that they have lost the desire to engage in enjoyable activities, feel sad, lack of appetite, sleep disorders, lack of motivation, inability to concentrate, and thoughts of suicide. These symptoms are the main diagnostic criteria for depression. Studies of people with anosmia also show that their depression progresses. "One study comparing people who lost their sight or smell after accidents showed that the emotional state of patients who lost their sense of smell generally continued to deteriorate over time," writes the author of the publication.            

Interestingly, depression can also cause a loss of smell. Patients with severe depression often complain to doctors of a sudden loss of the ability to smell odours. Meanwhile, patients' sensitivity to smells improves after treatment with antidepressants.          

Therefore, if I smell – I feel (I am full of life, I am happy)...

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