Dogs can smell stress from human sweat, breath: Study

Dogs can smell stress from a human's sweat and breath, according to a study conducted in the UK.

The research, published recently in the journal PLOS ONE, reinforces that dogs are highly sensitive and intuitive animals.

The research involved four dogs from Belfast – Treo, Fingal, Soot and Winnie – and 36 people. In every test session, each dog was given one person’s relaxed and stressed samples, taken only four minutes apart.

All of the dogs were able to correctly alert the researchers to each person’s stress sample.

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"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," said Clara Wilson, a PhD student at Queen's University Belfast.

"This is the first study of its kind and the knowledge could be useful when training service dogs and therapy dogs,” Wilson said.

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

Researchers collected samples of sweat and breath from participants before and after they did a difficult maths problem.

They self-reported their stress levels before and after the task and the researchers only used samples where the person's blood pressure and heart rate had increased.

The dogs were taught how to search a scent line-up and alert researchers to the correct sample. The stress and relaxed samples were then introduced but at this stage the researchers did not know if there was an odour difference that the dogs could detect.

“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," said Helen Parks, owner of Treo, a Cocker Spaniel.

"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!” Parks said.

In addition to Wilson, the study included researcher Kerry Campbell, an MSc. student in the School of Psychology.

They were supervised by Catherine Reeve, with support on collecting the human physiological measures from Zachary Petzel.