The physiological processes associated with an acute psychological stress response produce changes in human breath and sweat that dogs can detect with an accuracy of 93.75%, according to a new study published this week in the open-access journal PLOS ONE by Clara Wilson of Queen's University Belfast, UK, and colleagues.

Odors emitted by the body constitute chemical signals that have evolved for communication, primarily within species. Given dogs' remarkable sense of smell, their close domestication history with humans, and their use to support human psychological conditions such as anxiety, panic attacks and post-traumatic stress disorder (PTSD), researchers wondered whether dogs could be sensing chemical signals to respond to their owners' psychological states. [1]

Figure 1. Dogs Can Smell When You’re Stressed Out

Figure 1 shows the researchers then exposed these dogs to three different scents: a standard piece of gauze, a sample from an unstressed human and a stressed odor sample. The four dogs were incredibly adept at sniffing out the stressed sample, achieving a combined 93.8 percent accuracy rate. Though the study was small, the findings suggest that humans who are stressed out may emit odors that differ from their normal smell—different enough, at least, that dogs’ highly sensitive noses can tell something’s up. [2]

The researchers also collected before and after measurements of heart rate and blood pressure and responses to questionnaires that asked about the volunteers’ stress levels before and after the math task.

The dogs' accuracy at detecting the stress samples — from 90 percent to 96.88 percent — was even better than the researchers anticipated. [3]

A powerful nose

Dogs have 220 million olfactory receptors compared with humans’ 50 million, which makes canines “extremely effective at differentiating and identifying odors,” said Dr. Mark Freeman, clinical assistant professor in the department of small animal clinical sciences at Virginia Tech in Blacksburg.

All dogs have a strong sense of smell, but spaniels, terriers and lurchers would have likely used their olfactory receptors more regularly as hunting dogs, Freeman said. This could have been a factor in their success in the study, or it might be coincidental because others breeds like retrievers have excellent smelling skills as well. [4]

References:

1. https://www.sciencedaily.com/releases/2022/09/220929133419.htm
2. https://www.smithsonianmag.com/smart-news/dogs-can-smell-when-youre-stressed-out-180980866/
3. https://www.nbcnews.com/health/health-news/dogs-can-smell-stressed-new-study-shows-rcna49472
4. https://edition.cnn.com/2022/09/28/world/dogs-smell-stress-study-wellness-scn/index.html

Cite this article:

Thanusri swetha J (2022) Dogs Can Smell When You’re Stressed Out, Anatechmaz, pp. 418