Can Your Dog Smell Cancer?

Golden labrador retriever puppy
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Man's best friend has an amazing ability to sniff out potential threats to their humans. A dog's sense of smell is far superior to our weak human olfactory senses, with most breeds being able to detect a scent in an unfathomable proportion of parts per trillion. That means they can smell less than a drop of scent out of an entire Olympic-sized pool filled with water. Even your cuddly household pet has the ability to detect that scent apart from hundreds of thousands of gallons of water.


Medical Applications for Canines

Specific canine breeds have long been used as companions for the blind as guide dogs, but over the last few decades we've seen our furry friends emerge with new potential and responsibilities. Trained working dogs are now used as companions for people with epileptic disorders, for instance. These medical companion dogs are trained to monitor their human for signs of an impending seizure to include changes in breathing or posture, and to alert the human to the event. Companion dogs are also used to help calm owners who may suffer significant post traumatic stress disorder, or PTSD. Most recently emerged are the group of medical alert companion dogs who are trained to detect potential diabetic emergencies, such as very high or low blood sugars, in their owners. 

Law Enforcement

Local and Federal law enforcement agencies have taken advantage of the canine's nasal powers and frequently include highly trained K-9 units for seek and find missions.

Dogs are used to sniff out perpetrators, narcotics, explosives, and many other types of contraband. Teams of rescue canines were even in the spotlight following the 9/11 attacks, using their natural scenting talents to seek the living and deceased victims.

Current Research for Cancer Detection

Several illnesses have very distinctive odors -- once you smell them you never forget them.

Clostridium difficile, for example, lends a pungent odor to the stool of people infected with this bacteria. It is an intestinal bacteria that leads to significant diarrhea and is easily transmittable from person to person. One study quoted in the British Medical Journal highlighted a beagle's ability to detect this bacteria -- with a very high accuracy rate -- in the stool samples of test subjects.

It has since been theorized that canines, with their super sniffing power, might be able to detect the presence of certain chemical compounds present in people with cancer. The premise is that each type of cancer has its own odor, and a dog can be trained to detect that odor. Although this brings to mind dogs in laboratories sniffing test tubes, which has been done already, potential future applications would use the science of the dog's nose and how it detects smells, not the actual nose itself.

Future Applications

Researchers are working to detect exactly what biochemical compound the dogs noses are able to detect.

Once isolated, it is hypothesized that someday -- we're not there yet -- we will be able to create a new, minimally invasive tool, to detect early cancers modeling after the canine's olfactory abilities. If scientists could use this technology to isolate and detect specific odors related to cancer, we could potentially create a detection tool that can "sniff" out cancer in humans.

Although research to date hasn't used canines to detect colon cancer specifically, it does show promise in small studies that show dogs detecting prostate cancer in urine, and later stage breast and lung cancers in the exhaled breath.


Amundsen, T., et al. (2013).Can Dogs Smell Lung Cancer?Acta Oncologica.Accessed online via on February 20, 2015.

Bowmers, M.K., et al. (December 2012).Using a Dog's Superior Olfactory Sensitivity to Identify Clostridium difficile in Stools and Patients: Proof of Principle Study. British Medical Journal. Accessed online January 25, 2015.

Elliker, K.R., et al. (February 2014). Key Considerations for the Experimental Training and Evaluation of Cancer Odour Detection Dogs: Lessons Learnt from a Double-Blind, Controlled Trial of Prostate Cancer detection.;BMC Urology. Accessed online January 25, 2015.

McCulloh, M., et al. (2006).Diagnostic Accuracy of Canine Scent Detection in Early- and Late-Stage Lung and Breast Cancers. Integrative Cancer Therapies. Accessed online via SAGE Journals on February 20, 2015.

Palman, Deborah. (n.d.). K9 Options for Law Enforcement. United States Police Canine Association. Accessed online January 25, 2015.

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