Dogs can smell stress on human breath and sweat

Researchers at Queen’s University Belfast collected sweat and breath samples from 36 participants before and after performing a tense mental arithmetic task. Before and after completing the task, participants reported their stress levels, and the researchers used samples where the person’s blood pressure and heart rate had increased.

“The results show that we as humans produce different smells through our sweat and breath when we’re stressed, and dogs can distinguish this from our smell when relaxed – even though it’s from someone they don’t know,” Clara Wilson, a Ph.D. student at Queen’s School of Psychology, said.

The dogs, Treo, Fingal, Soot and Winnie, were trained to find a range of scents and then told researchers the correct sample.

Not a single bad alert

Four dogs were introduced to the relaxed and stressed samples when the researchers were unsure if there was a difference in smell that the dogs could tell apart.

Throughout 36 sessions, samples from each participant were given to each dog; in each session, relaxed and stressed samples were presented four minutes apart.

One of four dogs involved in the study.

All 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 sense stress only because of breathing and sweating, which could be helpful when training service dogs and therapy dogs,” Wilson added.

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