Although the human sense of smell is feeble compared to that of many animals, it is still very acute. We can recognize thousands of different smells, and we are able to detect odors even in infinitesimal quantities. The human nose is in fact the main organ of taste as well as smell. The so-called taste-buds on our tongues can only distinguish five qualities – sweet, sour, bitter, umami, and salt; all other ‘tastes’ are detected by the olfactory receptors high up in our nasal passages.
The Power of Our Perception
The reason we all feel it’s important to smell good is because it is. As humans, we believe you are what you smell like. If you smell good, it’s a reflection of your inner soul and overall self. If you smell bad or unpleasant, it sheds a negative light on you as a person.
Understanding how the sense of smell works has been heavily studied in recent years. Smell is an important sense as it can alert us to danger like gas leak, fire or rotten food but also is closely linked to parts of the brain that process emotion and memory. Unpleasant and bad smells can send pain signals to the brain to warn us of possible danger.
Certain scents can change the perception of your physical image, too! Want to shave a couple pounds off in minutes? Studies have shown that women who smell of floral and/or spicy scents are perceived to be 12 pounds lighter. It comes as no surprise that fragrance can be also be a vital tool in attracting the opposite sex. Scents like lavender and licorice have been proven to be especially alluring to men.
Research has determined that human attraction is a result of chemical messengers called pheromones. These chemicals trigger everything from physical and sexual attraction to deep emotions of love and empathy and can be detected subconsciously through a variety of avenues including, that’s right, the nose!
How Does the Sense of Smell Work?
The sense of smell, called olfaction—like the sense of taste—is part of the chemosensory system, or the chemical senses. The ability to smell comes from specialized sensory cells, called olfactory sensory neurons, which are found in a small patch of tissue high inside the nose. These cells connect directly to the brain. Each olfactory neuron has one odor receptor. Microscopic molecules released by substances around us—whether it’s coffee brewing or pine trees in a forest—stimulate these receptors. Once the neurons detect the molecules, they send messages to your brain, which identifies the smell. There are more smells in the environment than there are receptors, and any given molecule may stimulate a combination of receptors, creating a unique representation in the brain. These representations are registered by the brain as a particular smell.
Smells reach the olfactory sensory neurons through two pathways. The first pathway is through the nostrils. The second pathway is through a channel that connects the roof of the throat to the nose. Chewing food releases aromas that access the olfactory sensory neurons through the second channel. If the channel is blocked, such as when the nose is stuffed up by a cold or flu, odors can’t reach the sensory cells that are stimulated by smells. As a result, loss of much of the ability to enjoy a food’s flavor. In this way, the senses of smell and taste work closely together.
Without the olfactory sensory neurons, familiar flavors such as chocolate or oranges would be hard to distinguish. Without smell, foods tend to taste bland and have little or no flavor. Some people who go to the doctor because they think they’ve lost their sense of taste are surprised to learn that they’ve lost their sense of smell instead.
The sense of smell is also influenced by something called the common chemical sense. This sense involves thousands of nerve endings, especially on the moist surfaces of the eyes, nose, mouth, and throat. These nerve endings help to sense irritating substances—such as the tear-inducing power of an onion—or the refreshing coolness of menthol.
Variations in Smelling Ability
Our smelling ability increases to reach a plateau at about the age of eight, and declines in old age. Some researchers claim that our smell-sensitivity begins to deteriorate long before old age, perhaps even from the early 20s. But other scientists report that smelling ability depends on the person’s state of mental and physical health, with some very healthy 80-year-olds having the same olfactory prowess as young adults. Women consistently out-perform men on all tests of smelling ability. Although smoking does not always affect scores on smell-tests, it is widely believed to reduce sensitivity.
Schizophrenics, depressives, migraine sufferers and very-low-weight anorexics often experience olfactory deficits or dysfunctions. One group of researchers claims that certain psychiatric disorders are so closely linked to specific olfactory deficits that smell-tests should be part of diagnostic procedures. Zinc supplements have been shown to be successful in treating some smell and taste disorders.
Importance of Smell Today
We often take our sense of smell in our day-to-day lives for granted, and think we really rely on our eyes and ears. Smell has been an integral part of evolution and survival of the fittest for our species in the past. Although humans rely less now on smell for survival a huge importance is still placed on smell today for taste enjoyment and attracting a partner through use of perfumes.
Perfume houses around the world market their products as the latest and greatest new smell, which you can use to attract a mate. Entire industries exist as the humans have placed such a huge importance on smell. The fragrance industry is now bigger than ever and doesn’t just include retail sales of fragrances like perfumes.
Fragrances are added to many products as it makes us feel good. Smell is the only sense that affects the memory and emotion part of the brain. If we feel good when we buy a product then we are likely to continue buying it. This is why many companies add fragrance to their products such as soap, deodorant, and fabric softeners. Even those in the food industry use fragrance chemicals known as flavors or aroma chemicals to their products. Smell has become increasing important to us and as a result the industry has responded to these demands.
The Major Histocompatibility Complex
The reason we are attracted to some natural scents more than others is the Major Histocompatibility Complex (MHC), which is tied to your immune system. This intuitive scent detection system has evolved to let us choose the best partners for a genetic advantage in reproduction, since we tend to be most attracted to partners with an MHC composition much different than our own. When someone has an MHC with a composition unlike yours, they have stronger immunity toward different diseases and medical conditions than you do, so they naturally smell better to you. Interestingly, the body odor of other people also affects attractiveness on another level. A recent study revealed that political ideology can weigh into scent perception. Participants in the study were not able to identify the political beliefs of others by smell, but they did find that those with beliefs similar to their own simply smelled more attractive.
Scent and Sentiment
Curiously, remembering a smell is usually difficult—yet when exposed to certain scents, many people—of whom Proust is the paragon—may suddenly recall a distant childhood memory in emotionally rich detail. Some aromas even affect us physiologically. Laboratory researchers exploring human olfaction have found that:
- A faint trace of lemon significantly increases people’s perception of their own health.
- Lavender incense contributes to a pleasant mood—but it lowers volunteers’ mathematical abilities.
- A whiff of lavender and eucalyptus increases people’s respiratory rate and alertness.
- The scent of phenethyl alcohol (a constituent of rose oil) reduces blood pressure.
Mood is demonstrably affected by scent. But scientists have found that, despite some extravagant industry promises, the attraction value in perfumes resides strictly in their pleasantness, not their sexiness. So far, at least, store-bought scent is more decoration than mood manager or love potion. A subtle “look this way” nudge to the nose, inspiring a stranger’s curiosity, or at most a smile, is all perfume advertisers can in good conscience claim for their products—not overwhelming and immediate infatuation.
The Great Pheromone Hunt
For an animal whose nose supposedly plays no role in sexual attraction or social life, human emotions are strongly moved by smells. And we appear to be profoundly overequipped with smell-producing hardware for what little sniffing we have been thought to be up to. Human sweat, urine, breath, saliva, breast milk, skin oils, and sexual secretions all contain scent-communicating chemical compounds. Zoologist Michael Stoddart, author of The Scented Ape (Cambridge University Press, 1991), points out that humans possess denser skin concentrations of scent glands than almost any other mammal. This makes little sense until one abandons the myth that humans pay little attention to the fragrant or the rancid in their day-to-day lives.
Humans possess three major types of skin glands—sebaceous glands, eccrine (or sweat) glands, and apocrine glands. Sebaceous glands are most common on the face and forehead but occur around all of the body’s openings, including eyelids, ears, nostrils, lips, and nipples. This placement is particularly handy, as the secretions of these glands kill potentially dangerous microorganisms. They also contain fats that keep skin supple and waterproof and, on the downside, cause acne. Little is known about how sebaceous glands contribute to human body odor.
Sexy Genes
It was found that how women rate a man’s body odor pleasantness and sexiness depends upon how much of their MHC profile is shared. Overall, women prefer those scents exuded by men whose MHC profiles varied the most from their own. Hence, any given man’s odor could be pleasingly alluring to one woman, yet an offensive turnoff to another.
Raters said that the smells they preferred reminded them of current or ex-lovers about twice as often as did the smells of men who have MHC profiles similar to their own, suggesting that smell had played a role in past decisions about who to date. MHC-similar men’s smells were more often described as being like a brother’s or father’s body odor… as would be expected if the components of smell being rated are MHC determined.
Fooling Mother Nature
Perfume; daily, soapy showers; convenient contraceptive pills—all have their charms. But they also may be short-circuiting our own built-in means of mate choice, adaptations shaped to our unique needs by millions of years of ancestral adversities. The existence of couples who long for children they cannot have indicates that the Western dismissal of body scent is not benign.
Why Do Some People Smell So Much Worse Than Others?
Our sweat doesn’t really produce an odor itself. It’s the bacteria that we have on our skin. People are a petri dish walking on two legs. When bacteria have a wet or moist environment, they tend to thrive and grow. And when bacteria thrive and grow, they can produce their own odors.
There are two types of sweat glands. Eccrine glands are the most common, and can be found throughout the body, secreting sweat directly onto the skin. Apocrine glands can be found in areas like the armpits and groin, and dump their sweat into hair follicles first.
Unfortunately, while these glands create sweat that mixes with bacteria to make us smelly, we kind of need them. Because they control your body temperature. If you’re out running or jogging in the summertime, it can get hot, and your body has to cool down. By releasing sweat, you have an evaporative cooling effect, and you don’t get high internal body temperatures.
So we’ve all got bacteria. Why don’t we all smell the same?
One of the big reasons is diet, which makes a lot of sense, given the whole “you smell like what you eat” cliche. Wait, is that how it goes? Let’s say you eat garlic, onions, and spicy foods that have odors. As your body digests these foods, compounds are produced and released through the pores of the skin, and suddenly you smell like a refrigerator crisper that hasn’t been cleaned in months.
Other explanations for why human beings smell different from each other include hygiene and health. Consider one’s lifestyle. People who are dirtier than others are going to have more bacteria on their bodies — especially if they don’t shower often. Money and income can be issues if cleaning resources and products are scarce, most dramatically in extreme situations like homelessness.
People who are overweight may have folds in their skin, which are breeding grounds for bacteria. This is common with diabetics — whose problems with smell can go beyond having a few extra pounds. If a person has higher-than-normal blood sugar, there’s a condition called diabetic ketoacidosis, or DKA, and those patients tend to have more of a fruity smell to them.
