Do dogs actually smell our fear

Fluffology Blog

The body odor contains a lot of information. The composition of the odor can provide information about gender, emotional state or genetic relationship in humans. Many of these olfactory messages are not consciously perceptible to us, but sometimes influence our behavior on an unconscious level. In the case of disgust or fear, for example, the sweat contains odorous substances that subconsciously put other people in an alarm state. Such smell-transmitted messages are known as chemical signals. 1

Chemical signals in dogs and humans

In comparison to us, dogs have an exceptionally good sense of smell and often communicate with other dogs via smell messages. By means of urine markings, they leave messages that can be deciphered for other species. This includes information about gender or heat status. 2

Presumably, not only intraspecific chemical signals have a meaning. One often hears the assumption among dog owners that their four-legged friends would be able to smell fear.
Some study results actually suggest that human olfactory information also affects dog's behavior. According to research conducted in 2016, dogs seem to react to the scent of fearful people in a stressful and accelerated manner.3 Another common assumption is that human emotions have a direct impact on the dog. Can emotional states such as happiness or fearfulness be transmitted to the dog by means of smell? It is precisely this question that the Italian scientist Biagio D’Aniello investigated with his team. 4

Armpit sweat for science

In order to analyze a possible olfactory transmission of emotions, the dogs were allowed to move freely in a room individually for the experiment. There it was observed whether the confrontation of the animals with odor samples had an influence on their behavior towards the owner and a stranger. The smell samples came from people in different emotional states such as happiness and fearfulness.

For the odor tests, men’s armpit sweat was used, whom the researchers had previously put into a fearful or happy state using video recordings. The dogs participating in the study consisted of 31 Labrador Retrievers and 9 Golden Retrievers. In addition to the behavior, the researchers also observed the dogs' heart rates.

Anxiety and stress

When the dogs were exposed to the scent test from people in an anxious state, their heartbeat increased significantly. Such a significant increase in heart rate suggests an acutely stressful load. Furthermore, the faster heart rate is associated with an activation of the so-called sympathetic nervous system. The body is then in an increased state of tension in order to be able to react more quickly to actual or only perceived threats. According to the study data, the smell of scared people could actually cause stress in dogs. There is a risk that the stressed, excited four-legged friends will react more impulsively and show fear and aggression behavior more quickly. 5

In the present study, triggered by the fearful odor, a possible indication of more fearful behavior of the retrievers was observed. They showed less exploratory behavior, stayed close to their owners and made less contact with the stranger. When observing the behavior, the researchers were also able to identify many signs of stress such as increased panting, tonguing and big ears.

In comparison, the animals scented with the smell of happy people behaved less stressed. In this situation, the dogs were also more interested in the stranger and explored the common room more intensively.

Conclusion

The study provides another clue to dogs' ability to actually smell fear. It is rather unusual that olfactory messages are perceived and deciphered across species. This remarkable gift of the four-legged friends could have arisen in the course of domestication. In any case, it illustrates the close relationship between humans and dogs.