Dogs know what stress smells like — and can detect it in people

BELFAST, Northern Ireland — Dogs can sniff out stress, reveals a new study. Researchers in Ireland say the finding will help better train service and therapy dogs to make them aware of when their owner is under pressure.

Study authors collected sweat and breath samples from 36 people before and after they completed a difficult math problem. The participants also self-reported their stress levels both before and after the task.

The researchers only used samples where the person’s blood pressure and heart rate had increased. Four dogs, Treo, Fingal, Soot, and Winnie, then had to sniff out the stress samples.

They examined one person’s relaxed and stressed sample, and after a quick investigation, each dog was able to pick out the stressed-out smell. The results are published in the journal PLoS ONE.

dog sniffing
A study dog sniffing a person’s breath and sweat sample. (CREDIT: Kerry Campbell)

‘Dogs do not need visual or audio cues to pick up on human stress’

“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,” explains Clara Wilson, a PhD student in the School of Psychology at Queen’s University Belfast, in a media release.

“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 continues.

“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.”

One of the super sniffer canines that took part in the study, Treo, is a two-year old Cocker Spaniel.

“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,” says Treo’s owner, Helen Parks.

“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!”

South West News Service writer Alice Clifford contributed to this report.

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