The chemistry of attraction

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What would our relationship with others be like without their smell and our smell? As an integral part of our individual identity, it contains a lot of information about us: who we are, our age, our emotional state, our health and so on.
Each individual has their own particular scent. What is it made up of? Sweat, of course, but there’s more to it than that. Our immune system also affects body odour. According to German cellular biology professor Hanns Hatt and science journalist Regine Dee, co-authors of a book published in France under the title La Chimie de l’amour (“The chemistry of love”), it plays a leading role in the olfactory individualization process. “Every cell in our body has a type of distinctive protein, unique to each person,” they write. “These proteins are produced by the 30 to 50 genes known as MHC (major histocompatibility complex)”. They encode specific molecules for each individual. As these cells die and decompose, the by-products of these proteins end up in the sweat glands. They mix in with our sweat and give us our scent. Given that this process is so closely linked to genotype, scientists agree that no two body odours can be identical. However, various factors can alter this scent, such as emotional states, age and the menstrual cycle, but also certain diseases, such as cancer or diabetes. Acidity in the blood of diabetics consequently produces a characteristic smell in their breath and their secretions.
As time goes by, our hormonal balance changes and so does the bacteria in our body. In his article Odorat et histoire sociale (Smell and social history) published in 2000 in the review Communication et Langages (N° 126), French ENT doctor Patrice Tran Ba Huy refers to the disturbance of the sense of self associated with adolescence, a time at which “sexual identification is established in men through the smell of sperm, and in women through the smell of menstruation”. He also states that body odours are “heavily dependent on the social context in which they occur”. Whether “natural” or fragranced, he claims body odour is primarily determined by the psychological, emotional or sociological environment. “The olfactory self plays a vital role both in the development of personality and in communication between adults,” he wrote. Our smell is a function of our identity; it emerges from us and from our experiences throughout life.
In a more basic way, sweat and breath are also strongly influenced by diet. For example, garlic, onion, and spices like curry create an olfactory sillage that is rarely appreciated.

The T-shirt Test

Considering the parameters of our olfactory identity, the ability of new-born infants to distinguish the smell of their mother is striking. The late German ethologist Margret Schleidt explained how “infants are programmed to very quickly learn to identify smells”. At birth, the olfactory system has already been active for at least two months in utero, stimulated by odours circulating in the amniotic fluid. This means it is triggered instantly and develops early on compared to, for example, the visual system. Thanks to the mammary pheromone, the breast can be located without the need to see it.
We do not lose this olfactory recognition phenomenon over time. We retain the ability to feel a fundamental affinity towards members of our biological families. We can therefore identify our parents and siblings. In identification tests using T-shirts which have been worn by various people, the participants’ “favourite smell is most often that of the spouse” with “a 70-80% recognition rate”, according to Roland Salesse, a French agronomist, expert in the neurobiology of olfaction, and the author of Faut-il sentir bon pour séduire? (“Must one smell good to seduce?”). It has been suggested that men might, through their sense of smell alone, be able to choose a genetically-compatible sexual partner, limiting the risks of inbreeding. American evolutionary psychologist Glenn Weisfeld used the T-shirt test to explore conflictual relationships between members of the same family. In particular, he concluded that mothers have a preference for the smell of their teenage children and that brothers do not like their sister’s smell. Furthermore, “at puberty, children develop an aversion to the father” according to Hanns Hatt and Regine Dee. For Glenn Weisfeld, this involuntary repulsion is perhaps nature’s way of preventing incest. Itis an interesting and convincing hypothesis.
But Roland Salesse advises caution. “No one has ever done a sufficiently thorough analysis of the range of human odours to know what appeals to one person or another,” he counters. “It is still open to question.”

The scent of first love

The German psychologist Harald Euler believes that “olfactory comfort phenomena have been greatly neglected until now”. Yet, countless women have borrowed their partner’s pyjamas or T-shirt at least once to gain a sense of their presence. Euler also states that women and men “are similar on one point: the smell of their loved one raises feelings of happiness, closeness and satisfaction”. We must not forget that in this context, individuals are aware that the garment belongs to their spouse. So psychological conditioning has a powerful effect and this could be stronger than the role of smell. This is obviously not the only criterion for choosing a partner. A romantic encounter can take place “at 20-30 metres, because we are attracted to a certain body shape so we approach it”, explains Philippe Brenot, a French psychiatrist and marriage counsellor. We hear a voice, or we notice gestures or an attitude. “We approach if it pleases us, we recoil if it doesn’t,” says Brenot. But he insists that a person’s scent is a discriminating factor when we initially meet the other. For a relationship to last, the physical form of a person, the feeling of attraction and the way of speaking are not enough: smell is an important factor. Brenot refers to scents as secondary olfactory impressions. “I have heard stories of men or women who fall in love with someone who uses the same perfume as their first love”, he points out. “To smell a person or to be smelled by them is always to explore them on an intimate level and penetrate their innermost character,” says French philosopher Chantal Jaquet, co-author of Le Parfum et l’Amour (Perfume and Love). She argues that odour has the capacity to bring two bodies together and unite them to the extent that one feels they own the other.
Profound feelings are expressed through the sense of smell, which becomes the mediator of the deepest intimacy, even when the relationship is on the wane. “Ihad a case of a couple who were together for over 20 years. One day the wife said, ‘I can no longer stand the smell of his body’,” recalls Philippe Brenot. He believes his patient’s husband’s body odour had probably barely changed. A kind of lockdown occurs when a person’s smell is unattractive. At the same time, we can no longer bear the other’s remarks. “A kind of rejection,” he explains. “It’s real and it’s not uncommon.” It is through olfactory perception that his patient “ma­nages to say no when they have not yet acknowledged the estrangement that is in progress”, argues Brenot, adding: I think this sense is very profound.” The late French poet, writer and philosopher Paul Valéry expressed it well: “There is nothing deeper than skin.”

Hair – a reservoir of odours

Our response to sexual odours, however, is far from simple: our heart swings between disgust and desire. Philippe Brenot explains: “These substances are very powerful attractors and contain androgens, which are very similar to testosterone. And testosterone is the hormone of desire for both women and men.” These odours are produced by apocrine sweat glands and collect at the base of hairs which, Roland Salesse details, are found “under the armpit, around the pubis and the anus and on certain sexual organs (scrotum, foreskin, labia minora), around the nipple and in the ear”, and their secretion is stimulated by adrenaline.
According to Brenot, the hair is the most significant body part in terms of sex: “[Its] only function is to be a reservoir of odours. The skin is not a good reservoir of odour, even perfume. These hairs are placed in very specific regions to be closest to the partner’s nose.” Desire is governed by an olfactory imperative, writes the philosopher Chantal Jaquet: breathing in an odour appears to be “the perfect prelude, as it allows you to enjoy the other without frightening them away or being afraid of feeling connected”. So, according to Jaquet, wearing perfume is first and foremost a seduction technique.
A study by Craig Roberts of the University of Stirling (UK) and Jan Havlícek of the Charles University in Prague (Czech Republic) has also shown that women’s sensitivity to odours especially male odours increases at the time of ovulation. In the same way, men often prefer women’s odours at this time. “According to scientists, during these few days the body produces additional substances which give off a scent and enrich bodily odour,” say Hanns Hatt and Regine Dee. “The composition of the copuline in vaginal secretions also changes.” However, a woman’s perception of her capacity to attract does not alter at this time. And there is no change in women who take the pill, and who therefore do not ovulate.
In some cultures, attraction is intrinsically linked to olfactory rituals. For example, Polynesian women have a surprising practice that involves “applying perfume while standing over an oven dug into the ground”, as the French anthropologist Solange Petit-Skinner describes in the collective work Sentir. Pour une anthropolgie des odeurs (Smell. For an anthropology of odours). As it rises, the vapour of crushed coconut and fragrant flowers floats into the woman’s body. She then “exhales […] scented vapours” creating “a kind of aura around the person”. The vapours emitted are both captive and captivating. They override the natural body odour and openly invite amorous interaction.
According to Philippe Brenot, “it is in these intimate relations when the other senses, apart from touch, are often obscured that smell becomes particularly intense”. Often, “sight is suppressed” and “the man or woman make love with their eyes closed”. He adds: “During lovemaking, very often, we do not talk. With your eyes closed, you are guided and aroused by smell, and as you get closer to the other, the visual channel is diminished and the other senses are amplified.” Smell and touch help to increase arousal, triggering sensations of pleasure.

“Living in a vacuum”

Our sense of smell transcends the dichotomy of pleasant and unpleasant olfactory perceptions. It is enticed and stirred by interpersonal sensations that help us to stimulate a response in the other’s nose. Our response is often divided between attraction and repulsion. It is not uncommon for people having problems with their sense of smell to say they are suffering from “social disconnection”, or that they feel they are living in a vacuum. Our own olfactory identity contributes to our sense of belonging to the outside world through an invisible link created by odour.
In the context of romantic relationships, this desire for connection is intensified to the point that two bodies become one, their smells mingle and form an elixir oflasting pleasure. In Perfume: the story of a murderer by German writer Patrick Süskind, the central character of the novel, Jean-Baptiste Grenouille, is afflicted with an odourless body. Does he not take the desire for appropriation to the extreme by seeking to obtain the body odours of attractive young girls? This makes him the most desirable being on Earth, but it ultimately brings about his death.

• This article was originally published in Nez, the Olfactory Magazine – #03 – The Sex of Scent.

Main visual: Henri de Toulouse-Lautrec, In Bed, The Kiss, 1892. Source: Wikipédia