Dogs Can Detect when Humans are Stressed Out

VIVA – Dogs are known as one of the most loyal animals to humans. A new study reveals that dogs can detect humans when they are under stress. The stress response triggers physiological changes in sweat and breath, changes that dogs can detect by sniffing, according to a study published in the journal PLOS ONE in late September 2022.

Researchers from Queen's University in the UK collected samples of human breath and sweat before and after they completed a stressful task.

Then, they trained the dogs to identify odors that differentiated between the 'stress' and 'basic' samples. It was found that dogs were able to identify stress samples in 675 of 720 trials, or about 94 percent.

"This study definitively proves that when people have a stress response, their smell profile changes,"  a Ph.D. student at Queen's University and first author of the study, Clara Wilson said.

Dogs have long been used by humans as expert trackers to effectively identify everything from contraband to those infected with the COVID-19 virus. This is because dogs can smell volatile organic compounds called VOCs.

"While the dogs in this study underwent training to communicate that they were able to discriminate (smell), the performance found in this study suggests that there are changes in VOCs caused by acute negative stress that can be detected by dogs," the study explains.

More research is needed to find out how untrained dogs can communicate or interpret stress odors. But this study at least shows that dogs can smell the odors associated with stress in humans.

This disclosure may help further understand the relationship between guard dogs and owners who have anxiety or post-traumatic stress disorder (PTSD).

"They're often trained to spot someone crouching on the floor or starting to engage in self-injurious behavior," Clara Wilson added.

Co-founder and chief scientific officer at the charity Medical Detection Dogs, Claire Guest, who was not involved in the study, said medical alert assistance dogs were trained to alert people with complex health conditions when they were in danger of potentially dying by detecting changes in their smell.