It's official: Dogs can sniff out stress on humans' breath and sweat

"The findings show that we, as humans, produce different smells through our sweat and breath when we are stressed, and dogs can tell this apart from our smell when relaxed – even if it is someone they do not know," Clara Wilson, a Ph.D. student in the School of Psychology at Queen's, said.

The dogs, Treo, Fingal, Soot, and Winnie, were trained on how to search a scent lineup, then notified researchers about which sample was correct.

Not a single wrong alert

Four dogs were introduced to the relaxed and stress samples while researchers were not aware whether there was an odor difference that dogs could differentiate.

Throughout 36 sessions, every participant's samples were given to each dog; in every session, relaxed and stress samples were presented four minutes apart.

All the dogs correctly alerted researchers to each participant's stress sample.

"The research highlights that dogs do not need visual or audio cues to pick up on human stress. This is the first study of its kind, and it provides evidence that dogs can smell stress from breath and sweat alone, which could be useful when training service dogs and therapy dogs," Wilson added.

"It also helps to shed more light on the human-dog relationship and adds to our understanding of how dogs may interpret and interact with human psychological states."

"As the owner of a dog that thrives on sniffing, we were delighted and curious to see Treo take part in the study. We couldn't wait to hear the results each week when we collected him. He was always so excited to see the researchers at Queen's and could find his own way to the laboratory," Treo, a two-year-old Cocker Spaniel's owner Helen Parks said.

"The study made us more aware of a dog's ability to use their nose to "see" the world. We believe this study really developed Treo's ability to sense a change in emotion at home. The study reinforced for us that dogs are highly sensitive and intuitive animals, and there is immense value in using what they do best – sniffing!"