Olfaction – Smell

In the sensory exploration of the environment, the sense of smell is just as important as the other senses. In particular, smell plays an important role in reassuring your baby.

“5 senses for kids Foundation” shares what you should know about how the sense of smell works to support your child’s development.

The development of the olfactory system : we smell in the water!

The olfactory bulb, which is partly responsible for the sense of smell, is actually part of the brain. It is present in the human embryo from 8-10 weeks of pregnancy! And from the 12th week, this bulb is connected to the nasal mucous membrane, which is called (if you want to shine in society) the olfactory epithelium.

However, the olfactory system is not yet functional. In fact, the nostrils of the foetus are blocked by nasal plugs which only disappear between 4 and 6 months. Therefore, premature babies of 7-8 months have a functioning olfactory system and the sense of smell of the full term baby is already functioning.

In fact, the foetus is able to smell in the water of the amniotic fluid! And if this sounds incredible, you should know that when you breathe in the open air, the olfactory mucous membrane in your nose is in fact covered with a mucus which is a watery gel.

Practical exercise: put your finger in your mouth. It slips and it’s wet: it’s mucus. So you can smell in the water !

The trigeminal nerve, which innervates the eyes, nasal cavity and mouth (hence the “tri-“), develops earlier (between 7.5 and 10.5 weeks). It can be equated with to the sense of touch which is the first sense to develop in foetal life. After birth, it provides information about airflow, temperature, or the presence of irritants. The trigeminal nerve gives you information about the temperature and texture of food.

The more the pregnancy progresses, the more permeable the placenta becomes. So the foetus is bathed in its mother’s olfactory environment. Even before it is born, it smells its mother’s body odour, the odours of her food and possibly other products such as, unfortunately, cigarette smoke. Moreover, the placenta is impregnated with these smells: a mother who consumed a lot of curry testifies that she found this scent in her placenta after the birth of her daughter.

It seems that the child’s sensory experiences begin around the 8th week of pregnancy.

Practical tip: Be aware of the olfactory environment of a pregnant woman. If the air is full of smoke, toxic products or foul smells, the baby may be bothered !

The importance of olfaction from the first days of a child’s life

From birth, the baby is able to crawl to the breast to suckle. He is guided by the smell of the areola, because if one breast is washed and the other is left untouched, the baby will orient himself towards the unwashed breast. He will immediately recognise the smell of his mother. This reassures him. Because it has been engraved in the olfactory memory of the foetus, it will remain there for the rest of its life.

Tip: When a baby arrives at the nursery, we give him a cuddly toy with his mother’s smell. If he is too worried, ask his mother to bring a T-shirt. The olfactory sense helps to reassure the child.

Olfactory tests show that newborns are able to distinguish between different odorants. There may be an innate origin of pleasant or repulsive scents. For example, infants like vanilla and dislike rotten smells. But familiarity is a determining factor. For example, if the mother consumed aniseed during pregnancy, the newborn will prefer an aniseed-scented source to an unfamiliar one.

In addition to being essential to the infant’s nutrition and immune system, breastmilk is also an extraordinarily varied source of sensory experience, especially olfactory experience. At each feeding, the baby will smell the changing scent of his mother (depending on the day, the time of day, her food, her toilet), that of the members of the family and possibly of different places. In a few months, with the learning process reinforced by a secure environment (in the smell, warmth and maternal contact), the baby builds up an “odor library” (library of smells) which will lay the foundations for his future olfactory and gustatory preferences.

Practical advice: continue breastfeeding as long as possible, even if it is only once a day. The different scents in breast milk allow the child to expand its sensory repertoire. They benefit from a richer sensory experience.

What happens next ?

It has been found that at 15 months, breastfed children have a more varied diet than those fed with substitute milk. And as the odour variety of breast milk often reflects a greater variety in the family diet, this good start is reinforced to deploy a more diversified nutrition and a greater olfacto-gustatory curiosity around 6 years of age.

There are some very rare cases of anosmia (absence of smell). As no systematic test is carried out, it is sometimes noticed very late. For example, Kallmann-de Morsier syndrome (very rare, 1 in 10,000 births), although associated with anosmia or hyposmia (partial loss of smell) from birth, is often not detected until adolescence, when it is revealed by the absence or poor development of the genitalia. Other causes of anosmia or hyposmia are nasal obstructions, but these are usually effectively treated.

If talking about odours is difficult for adults (due to lack of education), the same is true for children as they acquire their vocabulary through experience. It is difficult to say whether the olfactory sensitivity of children under the age of 4 increases naturally with age or whether it is their ability to name odours (or their source) that develops, in the same way that they gradually put words to their experiences. It seems that by the age of 12, children have acquired an “olfactory level” equivalent to that of adults. In general, girls are better than boys. Biological and/or cultural origin? We are still wondering, but one (unfortunately unique) scientific publication shows that the female olfactory bulb contains twice as many neurons as the male. Perhaps a biological support for a sensory advantage.

Practical advice: “5 senses for kids Foundation” encourages you, from the earliest age of the children, to let them smell odours: the scent of flowers and plants, the odours of food, materials, etc. ; and to talk about it with them. You will help develop their sense of smell.

Helping children to use multi-sensory information

Accurate conceptualisation of a sensory entity rarely involves a single sense. It almost always relies on the contribution of several sensory attributes.

Take the example of an orange: the shape of the whole and its parts, the colour, the texture of the skin and its smell, the sweet acidic taste, the smell in the mouth, etc. All these facets are combined in a single conceptualisation.

All of these sensory facets, which use distinct sensory channels, converge in a global idea that is much more precise than that accessible via a single sensory input. It is by becoming aware of the multi-sensory aspect of natural objects that the child can acquire precise and generalizable concepts and words to describe them.

Let us be aware of the importance of using several of his senses simultaneously to have a more precise apprehension of what surrounds him. This is one of the interests of multi-sensory practice, which is at the heart of the mission of “5 senses for kids Foundation”.

I like it or I don’t like it ?

As mentioned above, there may be an innate origin of pleasant or repulsive scents. As early as 12 hours after birth, babies show different facial expressions depending on whether they are presented with pleasant, neutral or unpleasant odours.

In an earlier study, a small proportion (3%) of children under 3 years of age appeared to show an aversion to unpleasant smells. But by the age of 5, 72% of children show disgust. This parallels their rejection of faecal odours, which previously did not bother them.

Around the age of 5, this is also a pivotal age when children’s olfactory preferences become more similar to those of adults. Again, is this a biological or cultural effect ? One may wonder, but it is enough to observe the difference in appreciation of the smell of manure between urban dwellers and livestock farmers to see that socio-cultural factors are predominant.

Olfactory communication

We only attach importance to our body odours when we think they may be offensive. Strangely enough, we use scented deodorants and perfume ourselves so much that we can sometimes bother others, whereas our natural personal smell is quite discreet !

It is likely that our own smell is reassuring. We seldom consciously smell it because olfaction, like all sensory systems, ‘erases’ constant messages and is mainly concerned with what is new, especially the smell of others.

Almost 2000 chemical compounds have been identified in the human ‘bouquet’. This means that there are many sources of variation. There are nearly 8 billion of us on Earth who share a human scent, which varies according to our genome, our microbiota (all the micro-organisms such as viruses, bacteria or fungi), our sex, our hormones, the season, the time of day, the geography, our diet, our age and our state of health. There are four ‘smelling ages’ in humans: baby, child, adult and old man.

As we have seen above, the human babies find the breast and enriche their sensory repertoire thanks to their sense of smell. They are able to distinguish their mother’s smell (it is a scent that is never forgotten) from that of another woman. Beyond that, many experiments show that families recognise each other by smell. Both children and parents are able to recognise a family member by the smell of a T-shirt worn for a few hours. And even schoolchildren can recognise a friend by their sense of smell.

Later, in social relationships (isn’t it said that you can “smell” someone, or not ?) as well as in love relationships, body odour can play a role, although this is often forgotten, because (at least in explicit statements) women are more interested in the face and voice of men, while men are more interested in the body and face. However, it is known that women are more interested in male odour during the ovulation period, and this interest is suppressed by taking contraceptives. Men are also more attracted to female odour at the time of ovulation.

Our environment is full of olfactory cues that we usually ignore. When we ask about favourite scents, the smell of cut grass, of the forest, of the earth after the rain often comes up. But we could build a kind of scent clock that starts with coffee in the morning and ends with toothpaste in the evening.

Practical exercise: let yourself evoke all the scents you experience during the day. Pay attention to what comes with the smells. What has happened ?

All of this is the subject of multisensory learning, so that when we start recalling a memory through one sense (as in Proust’s famous madeleine), we can reconstruct all the circumstances of the event, including the emotions associated with it.

Our environment is full of olfactory signals that we usually ignore. When we investigate favorite fragrances, the smell of cut grass, the forest, the earth after the rain often comes up. All this is the subject of multisensory learning so that when we initiate the recall of a memory by a single sense (as in Proust’s famous madeleine), we can reconstruct all the circumstances of the event, including the emotions associated with it.

Fun activities to do with your child to develop their sense of smell

“5 senses for kids Foundation” recommends the following games.

  • You can play the “same/not the same” game. You need 3 tea balls, or 3 paper or cloth tea bags, or paper towels. Use these papers or cloths to make small packages. Inside 2 balls or packets, you put the same scented product. For example, cotton wool impregnated with the perfume of a relative, or dried lavender flowers, or freshly crushed garlic. In the third, you put a very different product, such as ground coffee or freshly crushed mint leaves. The child is asked: which balls smell the same ? Or among these three balls, one does not smell the same as the other two : which one ?
  • As in the touch game, we put products they are used to using or consuming in a bag (orange, chocolate, apple, shower gel, shampoo, etc.) and, as in the previous game, we hide a bit of the product in a tea ball or paper or fabric. The child is asked to smell the ball and to find the object in the bag (without seeing it, just by touching it). With toddlers, you may need to start with one object.