4 min read


Can Dogs Smell Cancer Cells?



4 min read


Can Dogs Smell Cancer Cells?


We all know that dogs have a great sense of smell and it’s much better than humans'. What may be surprising is their olfactory (smell) abilities, as dogs may be able to sniff out cancer in a human.

When you look at the statistics, it seems clear why this may be the case. When it comes to smell receptors, a dog has 25 times more than a human, which means their smelling ability is boosted by 100,000. The brain of a dog is dominated by its olfactory cortex compared to a human which brain is controlled by the visual cortex. A dog’s olfactory cortex is also 40 times bigger than a human.

We will take a look at how this amazing ability to smell translates into being able to smell cancer. 


Signs Dogs Can Smell Cancer

There have been known cases where dogs have smelt out cancer cells in a human. A dog who can smell cancer may nuzzle and sniff the flesh where they can smell the cells. They may then lick the area in question and fixate their eyes on the person they can smell it from, as if they are alerting that person to something. 

A dog may also start to act strangely and become more attentive, anxious and jump on the person in question and nudge the area where they can smell cancer cells.  

Body Language

If your dog has detected something abnormal about your smell, they may display the following:

  • Alert
  • Jumping Up
  • Sniffing
  • Raise Ears
  • Licking

Other Signs

More signs that your dog may give if they have detected cancer in you include:

  • Nudging Or Nuzzling The Area
  • Showing Obsession With The Area
  • Wide Eyes

History of Dogs Smelling Cancer


The first time this was suggested was in 1989, in a medical journal called The Lancet. However, in the decade following, publications regarding the matter were only occasional.

In 2004 and 2006, two studies which related to cancer detection in urine showed promising outcomes. The 2006 study highlighted that detection of lung cancer was 99% accurate, that said, both studies were pilots and only a small number of patients were involved. In 2011, a study revealed that breath samples tested by dogs provided results which were promising. In 2015, Huffington Post reported that dogs are able to detect bladder, breast, melanoma and lung cancer as well as being able to be trained to spot cancer in 93% of situations.

In 2016, in an interview with Entertainment Tonight, actress Shannon Doherty shared with the world that her dog had been the one who identified cancer in her breast before it was diagnosed by doctors. This kind of story is mirrored around the world and since then the NBC has stated that the British NHS are behind the first real clinical trial to investigate whether dogs can actually smell cancer cells.  

Science Behind Dogs Smelling Cancer Cells


As you can see from above, there have been many investigations as to whether dogs can sniff out cancer. But it begs the question, is there any scientific basis behind this? 

There have been numerous studies which highlight that dogs are able to detect cancer via breath samples. Doctors and scientists are now trying to create a breathalyzer test which will work as effectively as a dog’s nose. To date, it is still only dogs that are able to smell cancer when it is in the early stages. A study by Italian researchers revealed that dogs who were specially trained could detect prostate cancer from samples of urine and had 98% accuracy.

This then led them to see if two of these trained dogs could detect specific VOC’s related to prostate cancer from 677 participants’ urine samples. Out of these patients, 357 were healthy controls and 320 had prostate cancer, which ranged from low risk to metastatic cancer.

These dogs were also given urine samples from patients with thyroid cancer and some patients with benign nodules. The dogs then needed to alert whether or not the samples contained thyroid cancer or not.

These results were then completed to diagnoses made from surgical pathology reports and the results were identical in 30 out of 24 cases which shows an 88.2% accuracy rate. 

Training a Dog to Smell Cancer Cells


Cancer cells give off an odor which can be detected in the bodily fluids and breath of a cancer patient. A dog needs to be presented with hundreds of samples, to begin with. The dog needs to have exceptional scent-detecting abilities and a temperament which is calm and focussed. Training needs to involve a reward system for when a sample is correctly identified. Follow these 8 steps below to train a dog to smell cancer:

  1.  Play – play with a toy and your dog as often as possible. Use this method of playing with a toy as a reward for when your dog performs simple compliance commands.
  2. Introduce Scent -  create a scent wheel with two containers. One of these needs to obtain a scent which is easy to distinguish such as vanilla. The other needs to either be filled with water or remain empty.
  3. Reward Identification –  once your dog approaches the container which has the vanilla scent in it, reward your dog by playing with the toy mentioned in step 1.  
  4. Teach Alert – You now need to add an alert which your dog can do when they identify the scent e.g. ‘sit.’ Ask your dog to sit once they have identified the scent and then reward.
  5. Reward After Alert – only reward your dog with play once they can complete the alert and identify the scent.
  6. Add Scents -  slowly, begin to add more scents to your wheel.
  7. Teach Various Scents – now, teach your dog to alert with different scents.
  8. Provide Cancer Scents – finally, provide your dog with various samples of urine or blood plasma from cancer patients. Teach your dog to alert and identify these samples. Reward your dog only if they correctly signal and identify. If your dog makes a false indication, ignore your dog. 

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By Charlotte Ratcliffe

Published: 04/13/2018, edited: 04/06/2020

Wag! Specialist
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