Why dogs smell our breath – and what they read from it
It surely happens to many dog owners: You yawn heartily or exhale deeply, and suddenly, you have a dog nose sniffing your breath with interest. The question remains: Why do these four-legged friends do this?
Dogs and humans are a well-coordinated team. They often form deep bonds, communicate with each other, and can understand each other's facial expressions and gestures. But dogs aren't just loyal companions. They're also true masters at learning much about their companions based on smell.
While humans primarily consider visual criteria to assess others, dogs mainly use their noses. Dogs' sense of smell is considered exceptional. This is due, among other things, to the high number of olfactory cells in their nasal mucosa, their unique way of sniffing, and the processing of smell in the brain. Therefore, dogs rely entirely on their highly sensitive sense organs, even when living with humans.
Dogs perceive chemical changes through body odor
When a dog gets up close to the face of its beloved human and deliberately sniffs their breath, it gets much more than just an olfactory impression of their last meal. Dogs can detect chemical changes in a person's body odor and thus infer their owner's mood, detect health problems, or even notice hormonal changes.
When a dog sniffs its owner's breath, it's trying to find out more about their favorite person. This behavior is comparable to asking, "How are you today?" The sense of smell is an integral part of social interaction for four-legged friends. It helps them understand the world around them and find their way around it.
Dogs can smell stress and fear.
For many years, it was assumed that dogs perceive mood swings in humans primarily through their behavior, the tone of voice, and body language. However, various scientific studies in recent years have repeatedly demonstrated how cleverly these four-legged friends use their exceptional talent for smell to read people.
For example, in 2022, a British research team discovered that dogs can use breath and sweat to sniff out whether a person is stressed. In several rounds of experiments, the researchers demonstrated that trained dogs can distinguish the odor of a stressed person from that of the same person in a non-stressed state with an accuracy rate of almost 94 per cent.
In another study involving 40 Labradors and Golden Retrievers, researchers from Italy demonstrated that dogs can sniff out fear in humans. Using sweat samples, the scientists from the University of Naples Federico II determined that the dogs reacted particularly strongly to the smell of fear sweat, showing signs of stress and having a higher heart rate.
What dogs want to tell us with their looks
Biologists and zoologists at Linköping University in Sweden took their research a step further: In a study, they demonstrated that dogs not only recognize the emotions of their beloved humans, but are even infected by them. The researchers collected and examined hair and fur samples from humans and their dogs over an extended period and found that when the hair of the human subjects showed high cortisol levels, high cortisol levels were also found in the dogs' fur shortly thereafter. Cortisol is a hormone also known as the "stress hormone."
Against this backdrop, it might not seem so strange when dogs move their snouts very close to our faces, close their eyes, and sniff our breath with apparent concentration. Because for them, it's more than just an inconspicuous scent. Our breath is a rich source of information for our four-legged friends – and allows them to discover things about our mood that we may not have even noticed.