Woman Discovers Cancer Thanks to Her Dog: How a Constant Sniffing Led to a Life-Saving Diagnosis

A 50-year-old British woman discovered she had stage 3 rectal cancer, thanks to the keen sense of smell of her pet dog. The 51-year-old woman, Lindsey Thwaites became suspicious when her dog kept sniffing her bottom. This prompted her to visit the hospital, where she was diagnosed with cancer. Thwaites is currently undergoing chemotherapy and radiation treatments and is living with a colostomy bag. She said, “My dog sent me a message. I owe my life to his constant vigilance.” It is known that a dog’s sense of smell is more than 10,000 times stronger than a human’s. Let’s take a look at the amazing olfactory abilities of dogs and how they have been utilized.

■ Dogs’ Olfactory Receptors in the Brain, 40 Times Larger Than Humans

Humans perceive smells through the brain before the nose. Surprisingly, it is known that the olfactory receptors in a dog’s brain are about 40 times larger than those in humans. Dogs do not have a strong aversion to sniffing and analyzing new smell information, and they even find it interesting. When walking with a dog, you can see it sniffing the ground, soil, and objects. This is one of the dog’s instinctive detection behaviors. The number of olfactory receptors in dogs has been revealed to be ‘300 million’, 50 times that of the 6 million in humans.

■ Amazing Detection Ability

Conventional water quality measurement equipment shows a precision of about 1 ppm. However, dogs can distinguish and find specific substances at 1 in a trillion concentration. Dogs’ delicate and astonishing olfactory ability has achieved outstanding drug and explosive detection results at airports and customs. It also shows meaningful abilities in tracing the scent path of humans in crime and disaster situations and searching for missing persons.

■ Different Ways of Smelling?

Humans inhale air through the nose and immediately exhale it, exhibiting a ‘linear’ pattern of air exchange. Therefore, the human brain cannot analyze the exact smell and information of the inhaled breath for a long time. But dogs are different. The inside of a dog’s nose is ‘spiral’ shaped, allowing the inhaled and exhaled air to swirl and stay inside the nose for a long time. During this process, dogs can naturally classify and recognize various smell information floating in the air.

■ Classifying Diseases Like Cancer Cells, Diabetes, and Tuberculosis

As seen in Thwaites’s story, a dog’s sense of smell, 10,000 times that of a human, can even detect human diseases. In 2019, the American pharmaceutical company ‘BioScent’ experimented with four beagles, training them to distinguish between the scents of healthy human blood and the blood of end-stage lung cancer patients. The results were astonishing. After some training, three beagles distinguished between standard and lung cancer samples with an accuracy of about 96.7%. The remaining beagle showed no interest in olfactory training at all. The research leader explained, “This research has proven that dogs can be used to screen for cancer using their sense of smell,” and described a method of “creating a reagent that reacts to cancer cells that dogs can smell.”