Do Dogs Smell Fear? Yes. (And Here’s How, According to Science.)

When you are afraid — or even when you are happy — your body produces certain chemical signals that a dog can detect.

Photo of a growling black-and-white dog
Do dogs smell fear? The science says yes — if by “fear” we mean chemicals produced under emotional conditions of fear and stress. Photo: simonocampo999

Has anyone ever told you, “Don’t show fear” when you encounter a strange dog?

There is a long-held belief that dogs can literally “smell fear” and in some cases will react aggressively, leading to the above advice to not show fear to a dog.

This is actually good advice — but not for the reason you may think. Dogs often react to the emotions they pick up from their humans, so if you’re afraid, they will be too.

As for how dogs know you are afraid, well, there are a few tells. Body language is the biggest way we communicate with canines. But can dogs actually smell your fear?

The short answer is: Yes, dogs do smell fear. Keep reading, and I’ll explain more.

Photo of a cute little white dog looking a little nervous
Scent is a dog’s strongest sense. Photo: andrescarlofotografia

A Dog’s Nose Knows

Without question, the nose is the best source of information for the average dog.

“Some 200 million or so scent receptors make it much more sensitive than the human nose,” according to The Psychology of Dog Ownership authors Theresa Barlow, PhD, and Craig Roberts. Other sources put the number at around 300 million scent receptors for dogs.

For comparison, the average human has roughly 6 million scent receptors.

Let’s put this in terms of a real-world scenario: You just had a pizza delivered. You might smell just a pizza. Mmmm … pizza. But your dog’s nose will detect not just “pizza” but also the ingredients in the different cheeses, the spices in the sauce, the yeast in the crust, the people who handled the box and so on.

With scent being the dog’s strongest sense, it makes sense that they would use their nose to learn so much about the world around them.

Through their amazing scent receptors, a dog can sniff a person, a tree, another dog or just about anything and pick up a wealth of information. When they smell your pants leg, they’re detecting not just your laundry detergent but also where you’ve been, if you’ve been around other animals, other people’s scents and much more.

Their nose is so sensitive that dogs are often used as assistants in a wide variety of roles, such as tracking missing people, drugs and explosives detection and for many medical conditions that aren’t visible, including early-stage cancer, post-traumatic stress disorder and seizures. These last in particular lend themselves to the idea that dogs can smell the chemical changes in our bodies when there is an approaching anxiety attack or seizure.

Finally, as reported previously here at Petful, dogs are even being recruited in the global fight against the novel coronavirus that causes COVID-19. Once training is complete, the COVID-19 detection dogs are expected to be able to screen up to 250 people per hour to an extremely accurate degree, even if the humans are asymptomatic.

Close-up photo of a little brown dog's nose and whiskers.
In a recent study, dogs exposed to the sweat of a frightened human had higher heart rates and demonstrated higher stress indicators overall. Photo: careyne

How Do Dogs Smell Fear?

The question of whether dogs can detect an emotion has long intrigued researchers.

As reported in the journal Animal Cognition in January 2018, a team led by neurobiologist Biagio D’Aniello, PhD, of the University of Naples Federico II, conducted an experiment to see if dogs could detect chemicals related to human emotion in sweat.

The researchers took samples of armpit sweat from male volunteers:

  • They used sweat from men who were watching happy videos.
  • They also used sweat from men who were watching scary videos.
  • Finally, the researchers also used no sweat at all, to serve as a control for some of the test dogs.

These sweat samples were then randomly given to Labrador Retriever and Golden Retriever participants to sniff.

The study took place in a calm environment while the dogs were in the presence of their humans. The researchers wanted to know, “Do human body odors (chemosignals) produced under emotional conditions of happiness and fear provide information that is detectable by pet dogs?”

OK, I won’t keep you in suspense any longer: The experiment was a success. It showed that, yes, dogs can indeed “smell” fear — and happiness, too.

Dogs in the study who had been exposed to sweat from someone who was afraid demonstrated remarkably different behavior than the dogs exposed to “happy sweat.” Dogs exposed to the fear sweat had significantly higher heart rates and demonstrated higher stress indicators overall.

“Our findings suggest that interspecies emotional communication is facilitated by chemosignals,” concluded the scientists.

So, again, yes — dogs can in fact smell fear. Or, rather, dogs can detect the chemicals produced by the human body when we are afraid, and then understand in some fashion what those chemicals indicate.

And Not Just Dogs

Some of the same researchers went on to conduct a similar experiment with horses, the results of which were publicized in July 2018. And, surprise — it turns out that horses can smell your fear or happiness, too.

“These results are leading the way for further studies on human–animal communication through emotional chemosignals,” according to a November 2019 follow-up article published in the open-source journal Animal.

“What remains open,” the article pointed out, is if the smell of these chemicals is triggering “an automatic emotional response or whether the emotional responses are learned.”

Why You Shouldn’t Show Fear

Body language is extremely critical when dealing with canines.

Unfortunately, humans will inadvertently engage in behaviors that trigger dogs. For example, they might be:

  • Staring directly at or into the eyes of an unfamiliar dog. Direct eye contact with some dogs (and wolves) “is often a behavior in establishing or challenging dominance, so staring at a dog or wolf makes them uncomfortable, if not irritated,” says author Kirk A. Janowiak, who holds master’s degrees in both biology and ethology (animal behavior).
  • Facing a dog straight on. Again, this is challenging behavior to dogs. “They may seem friendly and happy as you approach, but if you loom over them, especially if you’re facing them head-on, you can cause them to have a meltdown,” said Dr. Sophia Yin, DVM, a veterinarian and animal behavior pioneer who died in 2014. Dr. Yin noted that “it’s better to stand facing slightly sideways and remain outside their personal space.”
  • Hitting or threatening a strike. Not only is this aggressive, but it also confirms to the dog that they must defend themselves. “When interacting with a dog, especially an unfamiliar one, avoid hugging, patting or petting in an overly familiar way,” said Dr. Yin. “Instead pet in a calm, gentle, relaxed manner.”

As a professional pet sitter and dog walker, I love dogs, I work with dogs, and I understand that sometimes being confronted by an aggressive dog can be scary. In these types of scary situations, it’s best to try to de-escalate the dog’s aggression:

  • Don’t stare directly into the dog’s eyes.
  • Turn your body slightly away so you’re not facing the dog head-on.
  • Speak calmly and don’t yell or strike — unless you have no other defense, meaning that the dog is attacking you.

So, while you may smell like fear, your body language is telling the dog you are not a threat. This may buy you enough time for the dog’s human to come and corral their dog or for someone to help you.

The above scenario applies when you have a few moments to try to head off an aggressive attack. Sometimes you don’t have the luxury of time, unfortunately. In my area this past May, 3 dogs escaped their house and attacked a FedEx driver who was making a delivery. The driver was taken to a local hospital, where she was treated for her injuries. Afterward, she was reported to be “alert but shaken.” Officials noted, “It could have been a lot worse.”

In those situations, do what you have to do to get clear and get to safety. If you routinely walk in areas in which you are exposed to loose, possibly aggressive dogs, consider carrying a citronella-based deterrent spray or an air horn.

When dealing with an aggressively approaching dog, remember to “do your best to remain calm so as not to escalate the situation with your own panicked behavior,” advises dog trainer Stephanie Colman.

Everyone feels fear. It’s impossible not to be afraid. Your body odor will reflect your emotional state via chemicals released by the brain. And dogs do pick up on that fear. But you can maintain some control by exhibiting the right behaviors.

For more on how dogs smell fear, check out this quick video:

YouTube player

Do Dogs Smell Fear? Final Thoughts.

A dog’s nose is a fascinating bit of biology, allowing the dog to register so much more of the world around them than humans could imagine.

When we look at it in this light, it’s understandable why dogs spend so much of their time using their nose. Even objects that we may find repulsive (feces, dead animals) hold a great deal of fascination for dogs because of the deep and complex network of information they’re receiving about the objects in question.

Humans don’t need that type of super-advanced scent network — but it does make you wonder what a day in the life of your dog is really like, doesn’t it?