Can Dogs Smell Cancer In Humans? The Facts Behind The Myths!
To some, it may sound far-fetched to say that your dog could tell you that you have cancer.
But there is plenty of anecdotal evidence out there that suggests this is the case.
So, can dogs smell cancer?
And if it is true that dogs detect cancer, are cancer sniffing dogs used to help diagnose the disease?
How do dogs detect cancer?
Does My Dog Know I Have Cancer?
You may have heard stories about dogs alerting their owners that they have cancer.
In most cases, the dog sniffs, scratches or nudges at the affected area persistently, as if trying to alert her human companion to something.
This leads some dog owners to ask “can dogs sense cancer?”
While these stories are amazing, some may conclude this is because the dog has become acutely familiar with her owner and her usual smell.
However, this ability would be difficult to use in a more routine, controlled setting like a clinic, where the dog is not familiar at all with the smell of the patient.
However, medical detection dogs are real and can be trained to detect a variety of illnesses.
Medical Detection Dogs
Medical detection dogs can be trained to smell particular chemicals that are released when a person becomes ill.
For instance, some people with type 1 diabetes have medical detection dogs that alert them that their blood sugar level has dropped, triggering the person to take action before they lose the ability to do so themselves.
These dogs even sleep in the same room as their human companion.
Some of these dogs will even wake up when they detect the scent and alert their human companion.
With a furry companion in tow, they can live a more normal life, without the worry of slipping into a potentially fatal diabetic coma.
There are other illnesses that medical detection dogs can sense, but the question still remains: Can dogs smell cancer?
Can Dogs Detect Cancer?
Most definitely they can, medical detection dogs are used to screen people for specific cancers.
While anecdotal evidence had been around for some time that they had this ability, in 2004, the first paper that robustly demonstrated that dogs could be trained to reliably detect the smell of cancer was published in the British Medical Journal.
A study published in 2011 found that a dog trained to detect the particular chemical present in the urine of prostate cancer sufferers correctly identified the samples in 31 out of 33 instances.
Interestingly, one of the samples was taken from a patient thought to be cancer free. However, the dog identified it as positive.
The sample was re-tested, and it was found that in fact the initial diagnosis was incorrect.
The dog had correctly identified the cancer.
Medical detection dogs have also been trained to detect chemicals that indicate bladder cancer in urine samples, lung and breast cancer in breath samples, and ovarian cancer in blood samples, to name just a few.
How Do Dogs Detect Cancer?
Dogs who can smell cancer are responding to the smell of a particular chemical released by the body when someone has cancer.
So, they are not really smelling the cancer itself.
The dog does not sit with the patient in person to detect these smells. Rather, a sample of the person’s urine or breath is taken.
Samples are presented to the dog.
Some samples are controls, meaning the sample was taken from a healthy person who does not have cancer.
Other samples are taken from individuals who the medical team suspect may have cancer.
The dog identifies the positive sample by sitting by or nudging the sample.
These dogs are not the primary method used to screen cancer.
They are used as a second line of screening.
Some cancers, such as prostate cancer, are particularly hard to diagnose.
In these cases, the dog’s reaction, along with test results, are combined to form the diagnosis.
Some studies have also sought to find out if the dogs are responding to the smell of the chemical alone, or if they are responding to other scents that are usually associated with cancer, such as inflammation, necrosis, bleeding, infection or even cigarette smoke.
Training Dog’s to Sense Cancer
Medical detection dogs are trained using positive reinforcement techniques.
When the dog identifies the scent and reacts in the desired manner, the dog is rewarded with either food or human attention.
The time this training starts varies from trainer to trainer.
Some studies have indicated that training can start once a dog is fully grown, and that dogs of any breed can be trained successfully.
Other trainers and organizations prefer to work with specific breeds and start training from a very young age.
Can Dogs Smell Cancer When They Detect It?
Can dogs smell cancer? Yes, they can. And with great success.
There is ongoing research into what we can learn from looking at the dog’s nose, and some researchers are developing electronic noses that may one day do a job similar to these medical detection dogs.
In the meantime, medical detection dogs do a very important, even lifesaving work.
While medical detection dogs are highly trained professionals, there is still something to be said for regular, family dogs.
They may not be trained, but they are still capable of picking up on smells that our human noses can’t detect.
This does not need you need to panic if your dog likes sniffing you—she is probably just being a normal dog.
But if your dog seems determined that something is not right over an extended period of time and this nudge is intensely focused on one part of your body, it might be worth a quick trip to the doctor.
We hope you have found this article interesting. Have you had any experience of dogs sniffing out cancer? Let us know in the comments section below.
References and Further Reading:
Amundsen, T., et al., 2013, “Can Dogs Smell Lung Cancer? First Study Using Exhaled Breath and Urine Screening in Unselected Patients With Suspected Lung Cancer,” Acta Oncologica
Clark, E., 2014, “Experience: My Dog Found My Cancer,” The Guardian
Cornu, J.N., et al., 2011, “Olfactory Detection of Prostate Cancer by Dogs Sniffing Urine: A Step Forward in Early Diagnosis,” European Urology, Volume 59, Issue 2, pgs. 197–201
Ehmann, R., et al., 2012, “Canine Scent Detection in the Diagnosis of Lung Cancer: Revisiting a Puzzling Phenomenon,” European Respiratory Journal
Horvath, G., Andersson, H., and Nemes, S., 2013, “Cancer Odor in the Blood of Ovarian Cancer Patients: A Retrospective Study of Detection by Dogs During Treatment, 3 and 6 Months Afterward,” BMC Cancer
McCulloch, M., et al., 2006, “Scent Detection of Lung and Breast Cancers Diagnostic Accuracy of Canine Scent Detection in Early- and Late-Stage Lung and Breast Cancers,” Integrative Cancer Therapies
Rooney, N., “A Medical Detection Role for Dogs,” International Animal Health Journal
Willis, C.M., et al., 2004, “Olfactory Detection of Human Bladder Cancer by Dogs: Proof of Principle Study,” The British Medical Journal
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Pippa Mattinson is the best selling author of The Happy Puppy Handbook, the Labrador Handbook, Choosing The Perfect Puppy, and Total Recall.
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