How Your Dog Knows When You’re Sick

When we have a specific bacterial or viral disease, our odour changes. Sometimes it is profound, but even if it is minimal, and we can’t smell it, this change is sufficient for a dog to detect it. Emotional changes in people are also noticed by dogs. Changes in emotions are physically manifested by the release of chemosignals by the body which dogs can sense. They also hear slight changes in tone of voice and recognise the difference of feelings and emotions in men. But what about severe systematic diseases?


One research has shown that dogs can detect cancer in human with its highly developed sense of smell. It goes up to detecting cancer with 97% accuracy. During this research, beagles were trained to distinguish healthy human blood serum from serum sampled from persons with proven malignant lung cancer. Further studies are planned in this area, but we can imagine how significant an impact it would have on medicine if trained dogs could tell us if someone has cancer before even high diagnostics could.


Malaria is another disease that gives a specific smell to infected human. It is a sort of molecular signature of the disease. A study conducted in the Gambia was including trained Labradors, who could distinguish the smell between malaria-infected persons and healthy ones. Children with diagnosed disease and healthy children have worn socks during sleep. In the morning, the dog was tested to detect which socks were worn by healthy ones and which were worn by kids with the disease and showed a great success. These findings can be used in both early noninvasive diagnostics of malaria as well as in detecting passengers with the disease at airports, to prevent the spread of the infection.

Parkinson’s disease

As researches about the conditions that dogs can smell evolve, it was discovered that Parkinson’s disease is in the group of disorders detectable by dogs. At first, scientist proved that there is a difference between the smell of persons with Parkinson’s disease and healthy persons. And after the positive result, there are attempts to train dogs to smell if the person has the disease in the beginning stage.


It is well known that diabetes is followed by ketone bodies in the blood and that people with uncured disease smell like acetone. However, there are changes in the scent of a person with minimal modifications of glucose levels in the blood that we can’t smell. However, dogs can tell even the slightest difference in blood level in sugar, and they can do it faster than a glucose monitor.

Future of diagnostics
With these latest findings, there is a whole new chapter in diagnostics opened. Further research will show if there are other diseases that dogs can detect. With noninvasive diagnostics by dogs, conditions can be treated in early stages, and also costs of expensive diagnostics will be reduced.