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Why are We Attracted to Bad Smells?


Do you ever bite into some blue cheese smeared across a cracker and wonder, "Why does this stinky cheese smell so good? Maybe you're cooking dinner and find yourself pondering over why you like the smell of garlic so much?

The reality, our sense of smell, is a cornerstone of our experience here on earth. It's a vital sense, and we rely on it for more than we realize. People who recently lost their sense of taste and smell after contracting the coronavirus discovered quickly how valuable these senses are to their everyday lives.

Smells create a range of emotional and physical responses; some are inviting while others are downright repulsive. Our sense of smell is a vital part of who we are and how we interact with the world. People that lose their sense of smell tend to wind up depressed without the additional stimulation.

Our smell can also be the most confusing of the five senses. Some people react differently to odors than others. For example, you might love blue cheese, but others think it's ghastly. Medical science spent decades studying the aspects of the "olfactory" system, and there are plenty of explanations as to why reactions to smells vary so widely in people.


Understanding Our Sense of Smell

Our smell experience occurs due to our reaction to chemical compounds in the air. Like the bodies of many other animals on the plant, our body reacts to environmental chemicals that produce scents. In fact, many animals use chemical odors to communicate and attract each other.

These hormonal phytochemical communication methods help animals understand more about one another. From sniffing urine, animals can determine the health and sexual maturity of the other animals, along with many other traits.

Our perception of smell comes from the way environmental chemicals interact with our brains. The olfactory system in humans works using the smell receptors found on nerve endings in the epithelium towards the bridge of the nose. These receptors react with the scent molecules dissolved in the air.

The olfactory bulb receives the nerve signals, converting them into our interpretation of smell. It's important to note that the olfactory system is actually a part of the brain. However, this system uniquely connects to the brain compared to the other four senses.

Unlike touch and sight, which receive processing through the thalamus, the hippocampus and amygdala are responsible for processing the data.

What's interesting is that these are the parts of the brain involved with creating memories. Therefore, it's easy for the brain to tie smells to emotions for easy recall and physical response to the stimulus. Smell receptors created by genes bind to classes of scent-producing molecules.

Individuals living with "specific anosmia" have a genetic condition. The genes dedicated to a specific receptor for identifying a particular class of scent molecules don't express in the olfactory system. As a result, it leaves the affected person unable to process and identify some smells.

Smells increase activity in olfactory receptors, and they also trigger the trigeminal nerve. This nerve runs between the brain and the rest of the skull. It detects our temperature and other properties involved with the physiology of the head.

When the trigeminal nerve interacts with scent molecules from hot peppers and mint, it creates the cooling menthol and spicy hot sensations associated with the experience of eating those foods. The olfactory system is also extremely sensitive to some smells.

Science shows that humans can detect smells in concentrations as low as one part in every 5-billion. Some experts think the human olfactory system is capable of identifying more than a trillion smells.


The Chemical Makeup of Scent Molecules

All scent molecules have some things in common. They are all volatile, meaning they can change between liquid and gaseous phases quickly. As a result, they tend to evaporate when exposed to room temperatures.

It's this characteristic that makes them readily available to your nose. Scent molecules can interact with other carbon-based molecules that constitute smell receptors, meaning many of them are also organic.

Like other bodily systems, the olfactory nerves are sensitive to specific, defined chemical structures. For example, if we look at the molecules of geraniol and 2-heptanone, both have similar carbon chains featuring an oxygen atom.

What's interesting is that the nose picks up the scent of geraniol (named after the smell produced by the geranium flower) as the smell of fresh blooming geraniums. However, it processes 2-heptanone as the smell associated with blue cheese.

The two smells are entirely different but very close in chemical structure. The difference comes from the sensitivity of the olfactory system. Some experts believe it also has something to do with how our memory and emotion contextually interacts with odors in our experience.

Even if you're a fan of blue cheese, if you bent down to smell a geranium and smelled stinky cheese instead, it would seem surprising, right?

Another good example of the sensitivity of the olfactory system exists in the difference between S-furaneol and R-furaneol. These two chemicals have near-identical structures. The only subtle difference between the two exists in the swapped positions of the methyl and hydrogen groups.

You'll recognize the scent of R-furaneol as sweet summer strawberries. However, S-furaneol has a subtle and almost unidentifiable scent.

The receptors capable of detecting the scent of fresh strawberries have such a specific mechanism of action that the change in data between the S and R-types causes a non-reaction in the olfactory system.

Some living organisms create organic compounds with the specific intention of benefiting from the odorous effect of the action. However, some interact with our system to create a particular smell.

The putrescine molecule produces a scent that smells of dead, rotting fish. Not so attractive, right? The bad smell comes from bacteria breaking down the amino acids in the flesh. That's what bacteria do; they break down the proteins into amino acids for sustenance.

However, to us, it's a smell that's a symbol of disease, and rightly so. Eating dead, rotting fish would likely make you very sick. Therefore the olfactory system interprets it as a bad smell, deterring us from interacting with the fish.

While the fish might smell nasty to us, it smells like a buffet from heaven to a hungry feral cat. So, what with the way the brain interprets different smells differently in people? Why does blue cheese smell great to you, but your kids can't stand the stuff?


Experiences Influence Our Sense of Smell

The differing reaction to rotting fish flesh between animals and humans is by design and less of a result of preferred diets.

The olfactory epithelium has over 400 receptor types, with each one is influenced by our genetic makeup and experiences. It's through this process that we learn how to react to certain smells in our environment.

It might surprise you to learn that the process of identifying scents starts as a fetus in the womb. We'll find whatever our mothers were eating appealing after birth. However, while the process of identifying smells begins before birth, kids must learn the difference between bad and good smells through experience.

As kids, we find many new smells appealing, and it's as we grow older, our experience defines and refines our reaction to the scent. Science shows that most kids have the same scent preferences as their parents by the time they reach eight years old.

The context of a smell is also a significant factor in determining its appeal. For instance, the smell of steaming cabbage coming from the inner soles of your shoes might seem somewhat offensive. However, the same scent coming from the kitchen signals dinner in your brain.

The US military has a project under development where they are trying to use scent-based dispersants as less-lethal crowd control alternatives to tear gas. However, the project has only managed to identify a few universal scents hated by everyone. Some of the compounds include sulfur-based odors, such as those found in excrement.


Different People, Same Smell

Our adaptable biology and diverse diet seem to define why there is so much ambiguity in our scent perception. As human beings, we are generalists. Therefore, we eat a wide variety of foods and live across a range of environments.

Since we are social creatures and rely on communication over force for community interaction, we pass these instincts down in our genetics. This methodology also plays a significant role in how we react to certain smells. Social experience shapes our reactions, and we pass those experiences down to the next generation through our DNA.

For example, you might develop an aversion to the smell of Chinese food after experiencing food poisoning. If you overeat pizza or get food poisoning with your order, the smell of tomato sauce and fresh mozzarella might be enough to have you running to the bathroom in disgust.

However, it's important to understand that we have some smells with genetic predeterminations. For instance, bitter flavors are accepted less universally as pleasant compared to sweet tastes. Bitter foods and beverages almost always seem to be an acquired taste we learn over time.

Aromatherapy also presents another example of human sensitivity to smell. The practice involves using the aroma of certain oil extracts for medicinal herbs and plants. The practitioner will either diffuse the oils in a humidifier, breathe in the steam, or apply them directly to their skin.

There’s no scientific evidence pointing to the efficacy of aromatherapy treatments in curing or helping alleviate disease symptoms. However, millions of people believe in this therapy. Medical science believes this belief in aromatherapy stems from the connection of the olfactory system to the memory.

If we smell a pleasant smell that reminds us of a positive experience in the past, it can provide a relaxing and encouraging effect on the mind and the body. For instance, the smell of fresh blueberries might remind you of your childhood, or roses bring back memories of affection from a loved one.

Some individuals process smells differently from others, and in some cases, we might find poisonous smells attractive. For instance, some people might like the smell of gasoline or paint.

Medical science is unsure of the reason for this phenomenon of liking the smell of dangerous substances. However, it believes there are two possible answers to the issue.

The first is that the smell might invoke positive memories, such as road trips. The second is that the volatile organic compounds (VOCs) found in these items may induce dopamine release in the brain, creating a positive reward feedback loop in the brain.

The brain finds the smell appealing, even though we know inhaling these fumes has a toxic effect on the body. As a result of the dopamine release, we may even develop a dependence or addiction to the dopamine release created by smelling these VOCs.


Inspect the Air Quality of Your Home

Your sense of smell deserves the best air quality available. If you're smelling VOCs or mold in your home, you could have a problem with the air quality and not realize the problem. Both VOCs and mold can cause severe adverse health issues in your and your family, especially if anyone has allergies.

Inspecting the air quality of your home gives you an accurate view of what you breathe every day. With MI&T, you get an inspection of your home's air quality, giving insight into the quality of the air you're breathing. When empowered with this information, you can take steps to remediate the air in your home and improve the quality of the air you breathe.

We can assist you in identifying mold infestations and the presence of high levels of VOCs that might damage your health. We can also advise on DIY methods to help you remove the mold and remediate the air. We're not a mold removal company, nor do we recommend any contractors.

At MI&T, you get an unbiased inspection of the air quality in your home, with no hidden partners waiting for your business. Contact us now to book your inspection; we'll work around your schedule.