Pressure also has an "odor" that can be smelled

A new study by researchers at Queen's University Belfast has found that dogs can sniff stress
from human sweat and breathing.
The study involved 4 dogs from Belfast – Treo, Fingal, Soot and Winnie – and 36 people
.
The researchers collected samples
of sweat and breath from participants before and after doing a math problem.
They self-reported their stress levels before and after the mission, and the researchers used only samples
of elevated blood pressure and heart rate.

The researchers taught the dogs how to search for odor sequences and reminded researchers to find the correct sample
.
Stressful and relaxed samples were then introduced, but at this stage, the researchers didn't know if the dogs could detect differences in odors
.

In each test session, each dog was given a sample of relaxation and nervousness at intervals of only 4 minutes
.
All dogs correctly alerted the researchers to each person's stress sample
.

Clara Wilson, a PhD student at Queen's University's School of Psychology, explains: "The findings show that we humans produce different smells through sweat and breathing when we are stressed, and dogs can distinguish between these smells and ours when we are relaxed – even if they don't know people
.
"

The study emphasizes that dogs don't need visual or audio cues to sense human stress
.
This is the first of its kind to study, and it provides evidence that dogs can smell stress just by breathing and sweating, which is useful
when training service dogs and treating dogs.

"It also helps to better understand the relationship between humans and dogs and deepens our understanding of
how dogs understand and interact with the human psyche.
"

One of the super sniffer dogs involved in the study was Treo, a two-year-old Cocker Spaniel
.
Its owner, Helen Parks, said: "As owners of a dog that makes a living sniffing, we were happy and curious to see Terreo participate in this study
.
Every week when we went to pick him up we couldn't wait to find out the result
.
He was always excited to see the researchers at Queen's College, and he could find his way
to the lab on his own.

This research made us more aware of the dog's ability to
"see" the world with their noses.
We believe this study did develop Treo's ability to
perceive emotional changes at home.
This study emphasizes to us that dogs are highly sensitive and intuitive animals, and there is tremendous value in using what they do best, sniffing!"

Clara Wilson, Kerry Campbell, Zachary Petzel, Catherine Reeve.
Dogs can discriminate between human baseline and psychological stress condition odours.
PLOS ONE, 2022; 17 (9): e0274143