Fido’s Nose Knows: How Your Dog Knows When You’re Sick

A dog’s sense of smell is more sensitive than the most technologically advanced man-made instrument. As mammals go, a dog’s sense of smell comes in third only after cows, which hold second place, and the African elephant, which tops the list at number one.

What makes a dog’s sniffer super? Dogs have 300 million olfactory receptors in their nose compared to 6 million for the average human. The acuteness of a dog’s sense of smell enables the detection of scent concentrations of one part per trillion. For example, a dog can sense a single rotten apple in a barrel among two million barrels!

The canine’s keen sense of smell has aided humankind for centuries and continues to do so in a variety of ways. Some dogs are trained to recognize specific odors which help keep us safe by sniffing out bombs, illegal drugs, and even solve crimes by tracking the scent of suspects at large, or missing persons.

Futhermore, dogs can tell when their human companions are not feeling well and have been known to guard them during times of injury or illness. Leading to the assumption that dogs are clairvoyant. They are not. The reason is scientific.

The canine nose functions differently from a human nose. When we breathe, we inhale and smell through the same air passage in our nose. When a dog inhales, a fold of tissue inside their nostril separates and creates two different flow paths, one for olfaction (smelling) and one for respiration (breathing).

When we are ill or have an off mood (a person’s mood can be an indicator of a larger illness), this will trigger a dog’s sense of smell. Dogs can detect when a person’s natural odor is off because bacteria and viruses that are present in a person’s body emit chemical signals through the person’s skin, urine, feces, breath, and sweat.

Dogs perform double duty as companions and protectors, especially when it comes to their human’s health. Diabetic alert dogs have alerted their type 1 diabetic human companions that their blood sugar levels were off before any obvious symptoms or blood tests were taken.

Ongoing research also suggests that dogs can detect several types of cancer in humans. A case study published in BMJ case reports described a case where a dog helped its owner discover a malignant melanoma by persistently licking him behind his ear.

So, the next time you are sniffed by your favorite pooch, know that your furry friend literally has your back.

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