Dogs Can Smell Your Stress, But How Do They React to It?

Research has established a dog’s ability to smell many diseases, possibly even before a diagnosis is made. These have included cancers (reviewed in Edwards et al., 2017), bacterial infections, seizures, and humans infected with COVID-19.

Diseases such as cystic fibrosis and the infections that may come with it and their seriousness to the lung are usually dependent on airway sampling at 2 to 3-month intervals, which permits bacterial infections to exist and grow. More readily available means of detecting these infections would seem to be a prudent method of ensuring high-quality healthcare for these patients. Might dogs be the answer?

It is now becoming evident that one means of detecting a variety of illnesses, whether viruses, bacteria, or others, may be monitored through the individual’s breath. Breath sampling, therefore, seems to be a desirable means of ongoing evaluation for potential illness or the presence of disease.

One of the most promising non-invasive diagnostic methods that has also attracted great research interest during the last years is breath analysis; the method detects gas-analytes such as exhaled volatile organic compounds (VOCs) and inorganic gases that are considered to be essential biomarkers for various disease types.

This type of analysis provides a less complicated method than procedures such as gastroscopy, laryngoscopy, and coronary angiography. In the process, it increases patient compliance for ongoing evaluation. Where do the dogs fit into this medical evaluation?

Research has indicated that more than 2000 VOCs have been detected in the breath, including hydrocarbons, alcohol, ketones, certain acids, aromatic compounds, sulfides, and other substances. These substances in the breath are associated with the environment and the person’s habits and can also be created by body temperature and metabolism.

Those VOCs produced in the airway or other parts of the human body are prime for trained dog scent detection. It should be noted that a dog’s scent detection can be more significant than 40 times a human’s ability to sense a scent. Some estimates place a dog’s sensitivity in this area at up to 10K that of humans, depending on the breed and the situation.

In 1989, the first report of a dog sniffing out its owner’s melanoma was reported. The woman had a pigmented lesion on her thigh, which had been removed and confirmed to be malignant melanoma.

She had been alerted to a problem by her dog repeatedly sniffing at the mole, and, at one time, the dog attempted to bite off the lesion when the patient wore shorts. Undoubtedly, the dog’s actions were primed by the scent of cancer, and it was trying to aid its owner. It has been noted that dogs frequently will smell and lick infected wounds.

What about stress? Breath and sweat samples have been used in recent studies to train dogs to differentiate between samples of stressed individual odors and those of blank samples.

Volatile organic compounds (VOCs) in the breath and sweat of stressed individuals were accurately detected between 90 to 96% of the time by trained dogs, indicating an understanding of the dog’s ability to detect stress. The researchers suggested that this ability to detect stress would be especially valuable for individuals with emotional support dogs or service dogs that could help them through periods of emotional turmoil with their support.

If a dog can detect stress because of the VOCs detected, would it be reasonable that they could also detect other emotions? The question will prompt others to research an extension of this study and may turn up some intriguing answers regarding the place of dogs in medicine and our emotional lives.

Considering the ability of dogs to be loving, faithful medical assets, can we make a case for dog ownership by healthy individuals even where dogs may not be permitted?

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