Can dogs really smell cancer?

Dogs are not only renowned for their ability to track people or detect drugs at airports, they can also sniff out cancer. How is our four-legged friend’s sense of smell so dazzling? 

A nose for odors. Image: Flickr

What’s special about their nose? 

Dogs are awesome, more so because they possess an exceptional gift of sniff. Olfaction, the process of smelling, is the most important sense to a dog. Their sense of smell is 10,000 to 100,000 times more sensitive than ours. It is not surprising, since there are more than 220 million olfactory receptors in a dog’s nose, compared to only 5 million in humans. (Olfactory receptors detect odor molecules in the air and send signals to the brain.) In addition to having more olfactory receptors than us, dogs possess a rich supply of nerves to transfer odor signals. Also, the brain region devoted for scent analysis is more developed in dogs, explaining why their sense of smell overpowers our own.

A dog’s nose does not function like ours. When we inhale, we use the same airways to breath and smell, but dogs can separate these two functions of the nose. Air splits into two pathways with a fold of tissue in the dogs’ nostrils. While most of the air inhaled travels down to the lungs, the rest detours to an area dedicated to smelling at the back of the nose. Mucus in this region traps incoming scent particles until the olfactory receptors can detect them and report to the brain.

Top sniffers

When we exhale, air leaves through the same pathways as it entered, pushing out any incoming odor molecules. This prevent scent particles from accumulating in the nose and being detected by olfactory receptors. But dogs have developed a specialized pathway for air exit while still maintaining their smelling capacity. Sometimes dogs need to take more than one sniff to identify a smell. So to allow new odor molecules entering the nose, the spent air flows out through the slits on the sides of dogs’ nostrils. Because their smelling ability is not interrupted by air exit, dogs can sniff more or less continuously.

Detecting the smell of cancer

Researches have identified that trained dogs can sniff out various types of cancer, including prostate cancer. At the moment, traditional tests used to diagnose prostate cancer are not 100% reliable. In other words, if a man takes this test, there is a high chance he will receive a positive result even though he does not have the disease.

Meanwhile, numerous studies have backed up the idea that dogs can sniff out cancer in urine with a high success rate. A research in France has discovered that specially trained dogs can successfully identify prostate cancer by smelling urine 91% of the time. It is thought that dog’s sense of smell can be used as a second-line check after the conventional prostate cancer test.

So you might be wondering whether you can get your dog to check out your cancer risk. Sorry to disappoint you but there is no proper research to prove that untrained dogs can detect tumors. So don’t freak out just yet if your pet behaves strangely; you need real cancer screening to diagnose cancer!

Worth watching

Video: How do dogs “see” with their noses? 

Video: Dogs can smell cancer