In today’s Pet Bulletin, we explore the fascinating possibility that dogs can detect human stress through their extraordinary sense of smell, drawing on scientific research and real-life examples.
There is a reason we call dogs our primeval friends. Dogs have accompanied humans for millennia, whether as trusted companions at home, partners on hunting expeditions, or sled runners in the Arctic regions. But there may be a surprising reason why modern pet parents feel such a strong connection with dogs: dogs may be able to detect signs of human stress.
Many dog owners would agree that when they return home after a long, stressful day at work, drop their bags, and sit down on the couch, turning on the TV without even realizing which channel is playing, their dog quietly approaches them. The dog observes them for a moment, seemingly unusually attentive to their behavior and facial expressions.
The dog stays closer than it normally does. It keeps staring at you, its eyes following your every movement, blinking frequently. We often describe moments like this by saying, “My dog can sense that something is wrong.” Research suggests that there might be ‘something’ behind that intuitive response. Maybe, your dog can smell it.
Stress has a smell
A 2022 study published in PLOS ONE tested whether dogs could distinguish the odor of people experiencing psychological stress. Researchers collected breath and sweat samples from 36 people before and after they completed a stressful mental arithmetic task. Four dogs were then trained to recognize and identify the samples.
The dogs identified the samples with the presence of stress with a combined accuracy of 93.75%, suggesting that acute psychological stress produces changes in volatile compounds from human breath and sweat that dogs can detect (Wilson, et al, 2022).
But you have to understand first how the process works inside the tiny dog brain. The dogs were not necessarily thinking, “My human is stressed.” Their focus was on detecting an odor that smelled unusual.
And the odor may affect them
Another study published in Scientific Reports in 2024 took the question further. A group of researchers exposed 18 dogs to odor samples collected from people they were not familiar with. The people providing the samples had previously been exposed to either stressful or relaxing activities. The dogs were then given a cognitive-bias test involving food bowls placed at different locations.
When exposed to stress-associated odors, the dogs became less likely to approach an ambiguous location. The researchers interpreted this as evidence that human stress odor could influence canine behavior and make the dogs more cautious (Parr-Cortes, et al, 2024)
So the interesting discovery is not simply that dogs can smell stress. It is that what they smell may change how they behave afterwards.
But can dogs actually “read” our emotions?
This is one question that has presumably kept millions of dog owners wondering for generations across the globe.
A 2018 study found that dogs responded differently to human body odors associated with fear and happiness. Dogs exposed to fear-associated odors displayed more stress-related behaviors and changes in heart rate, suggesting that emotional information can be transmitted from humans to dogs through body odors (D’Aniello et al., 2018). The researchers suggest that dogs may detect volatile chemical compounds released through human breath and sweat, which can change with a person’s emotional state and trigger different physiological and behavioral responses in the dogs.
But a question remains: is detecting a chemical signal the same as understanding an emotion? Your dog does not need to understand the sentence, “You had a terrible day at work.” It may simply detect that something about your usual chemical signature has changed.
What this means for the future
This could have enormous implications for the development of futuristic pet products and the integration of artificial intelligence into them.
AI systems are increasingly capable of identifying patterns in animal behavior and biological signals. A simple AI-integrated cat litter box, for example, can detect changes in a cat’s bathroom habits that may be associated with health problems. Combined with chemical analysis, future systems might help us recognize biological changes that remain invisible to human senses.
So, don’t presume yet: “Your dog knows you are anxious.”
But perhaps: “Your dog’s environment contains chemical signals associated with human stress.”
This might not sound particularly exciting to pet enthusiasts who are keen to follow every new technological integration into their pet products. But that is what scientific development often looks like: one small block at a time. Over time, those individual blocks can become something as extraordinary as the Pyramid of Giza.
Perhaps the future of pet technology is not teaching machines to make animals speak human language. Perhaps it is teaching humans to understand how much animals have been sensing all along.
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Scientific References
Wilson, C., Campbell, K., Petzel, Z., & Reeve, C. (2022). Dogs can discriminate between human baseline and psychological stress condition odours. PLOS ONE, 17(9), e0274143. https://doi.org/10.1371/journal.pone.0274143
Parr-Cortes, Z., Müller, C. T., Talas, L., Mendl, M., Guest, C., & Rooney, N. J. (2024). The odour of an unfamiliar stressed or relaxed person affects dogs’ responses to a cognitive bias test. Scientific Reports, 14, 15843. https://doi.org/10.1038/s41598-024-66147-1
D’Aniello, B., Semin, G. R., Alterisio, A., Aria, M., & Scandurra, A. (2018). Interspecies transmission of emotional information via chemosignals: From humans to dogs (Canis lupus familiaris). Animal Cognition, 21(1), 67–78. https://doi.org/10.1007/s10071-017-1139-x
