Imagine this: you're walking past a petrol station and you take a deep breath. Or you instinctively smell your dog's wet fur deeply. Perhaps you smell the skin behind your ear after a long day. These moments point to one of the strangest aspects of human nature: our attraction to scents that we should logically find disgusting.
Modern neuroscience reveals this isn't a simple quirk but rather a complex interplay of evolutionary biology, neurochemistry, and psychology, honed over millions of years to shape our survival and experiences.
We consider certain smells socially unpleasant, yet many people find them attractive. The sharp, chemical scent of petrol has captivated people for decades, while the mouldy aroma of Roquefort cheese has become a gastronomic delight. The smell of marker pens is familiar from our school days, yet wet concrete can be soothing on rainy days.
Human olfaction is extraordinarily subjective. What one person finds disgusting can be heaven for another. The characteristic smell of household pets, the dusty scent of old wardrobes, or even the sweaty smell of a gymnasium — each can evoke positive associations in those for whom they represent safety, home, or pleasant memories.
Cultural background also fundamentally shapes our perceptions. Fermented foods, for example, such as Korean kimchi, German sauerkraut, or Nordic hákarl, often have strong, initially repulsive odors, yet they are considered delicacies in local cultures. This suggests that the judgment of a "bad" smell is largely learned behavior. These preferences aren't random whims—they're deeply rooted in biological and psychological mechanisms. Our brain tends to associate scents with simultaneous emotions and experiences, so an originally unpleasant smell can become beloved if we encounter it in a positive context.
Not all bad smells are equal. Some trigger deep revulsion, while others are surprisingly comforting. Here's what research suggests:
Uniquely among our senses, the olfactory system has direct connections to the brain's limbic system—specifically the amygdala and hippocampus—which are the primitive brain structures governing emotion, memory, and motivation (Herz, 2016). This neural architecture is distinct from our other senses like sight and sound, which are first relayed through the thalamus before reaching the cortex. Olfaction largely bypasses this thalamic relay, giving it a more direct and unfiltered line to the brain's emotional and memory centers (Shepherd, 2004).
This direct pathway explains why the dusty smell of an old book can transport us through time with such startling immediacy. The chlorinated pool smell, for example, reminds us of childhood summers, while the hospital disinfectant smell can give a sense of security. The brain doesn't distinguish between "good" and "bad" smells—it just makes powerful, lasting associations.
From an evolutionary perspective, our attraction to certain "dangerous" or pungent smells may have conferred a survival advantage. For example, the earthy scent after rain, known as petrichor, is caused by a compound called geosmin, which is produced by soil bacteria. The presence of these compounds may have signaled a source of fresh water and a healthy, thriving environment to our ancestors (Becher et al., 2020). Similarly, the smell of wood smoke, while dangerous up close, signaled the presence of fire for warmth, cooking, and protection from predators at a distance. These deeply embedded neurological associations persist even today.
Even the factory smell of toilet paper can suggest safety to our modern brain—it symbolizes cleanliness and hygiene.
| Petrichor (Wet earth) | Signalled fresh water and safe environment after rain |
| Wood smoke | Meant fire for warmth, cooking, and protection from predators |
| Mushroom/Mould scents | Indicated soil fertility and potential food supplies |
| Chemical scents | Associated with modern cleanliness and sanitation |
The phenomenon, often called the "Proust effect" in reference to Marcel Proust's novel, posits that scents are among the most powerful memory triggers (Chu & Downes, 2000). The smell of sage tea reminds us of sick days, the ice cream cone scent of summer festivals, while the smell of unwashed clothes can give a safe, homely feeling.
This is why cat litter smell can become attractive in cat-owning households, or the scent of dog fur for dog lovers—these become the scents of home and love.
Perfumers have known for centuries that the most alluring fragrances often contain elements that are unpleasant in isolation. Indole, for example, is a compound present in white florals like jasmine but is also characteristic of fecal matter when smelled on its own (Burr, 2008). Another compound, skatole, contributes to the smell of decay but, in heavy dilution, imparts a warm, animalic depth to fragrances.
These seemingly repulsive ingredients, along with materials like civet musk or ambergris (a whale excretion), function as powerful fixatives. They anchor more volatile floral and citrus notes, adding longevity, complexity, and a mysterious warmth that a purely "clean" scent could never achieve (Turin, 2006). Modern fragrance creators continue this tradition, deliberately using synthetic notes of diesel, rubber, or even onion to add an element of surprise. This principle of "beautiful ugliness" proves that true attraction often lies in powerful contrasts.
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Our love for "bad" smells isn't a quirk - it's a fundamental part of our human nature. Millions of years of evolution, personal memories, and cultural programming all contribute to making a petrol station smell like poetry, and cheese mould scent like paradise.
Perhaps it's time to accept: sometimes the most wonderful experiences come from the most unorthodox sources.
Becher, P. G. Geosmin as a warning chemical that signals the presence of harmful microbes to invertebrates. Nature Communications.
Burr, C. The Emperor of Scent: A True Story of Perfume and Obsession. Random House.
Chu, S., & Downes, J. J. Odour-evoked autobiographical memories: Psychological investigations of Proustian phenomena. Chemical Senses.
Herz, R. S. Aromatherapy facts and fictions: a scientific analysis of olfactory effects on mood, physiology and behavior.
Herz, R. S. The role of the amygdala in the perception of odor valence and pleasantness. Neuroscience & Biobehavioral Reviews.
Herz, R. S. Neuroimaging evidence for the emotional potency of odor-evoked memory. Neuropsychologia.
Shepherd, G. M. The human sense of smell: are we better than we think?
Turin, L. The Secret of Scent. Ecco. (2006).