Can Dogs Smell Cancer? What Your Dog’s Nose Is Telling Them –


Yes, dogs can smell cancer. They can even smell it “in situ”, or at stage zero.

Let’s take a closer look at why dogs are even interested in smelling cancer in the first place. Why would a dog be interested in smelling cancer? There has to be something in it for them. Dogs have lived side by side, co-evolving with man for well over 100,000 years. Man provided shelter and food for the dog (and early wolf), and in turn, the dog warned man against impeding danger, pointed towards prey and food, and eventually guarded our livestock and crops. We provided for the dog, and the dog used his nose to help provide for, and protect, us. The key here is that the dog used his nose for our benefit. Top dog and wolf evolutionists and biologists are now saying that man may have never made it past the agricultural stage without the dog (and his nose).

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.

Without these dogs, people with uncontrollable type 1 diabetes have to test their blood sugar level once an hour, 24 hours a day.

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.

So why would a dog want to smell cancer? The answer is simple: if something is wrong with us, this will affect the dog. If we are sick, this could directly affect our ability to provide food and shelter for the dog. The dog “notices” small changes which could signify that we are in trouble. For example: if I have a cut on my leg, under my jeans and socks, why does almost every dog find and sniff the cut? They are noticing a change, or something different, that’s not like the rest of us. This small change can mean that we may become incapacitated in some way, which means the dog may suffer. Most prey animals which get caught and killed by predators are sick or injured in some way. The slowest, or sickest bird gets caught. Imagine the years of a dog learning to find the “sick” scent. Or better yet, the dog is “reinforced” (eating the sick bird) by having the sick scent paired with the eating of the bird. Smelling disease helps the dog catch his own prey, as well as larger prey for man. The sick scent is very important for the dogs (and mans) survival.

Dogs can smell in parts per trillion. An example of this is: one cc of blood, diluted into 20 olympic sized swimming pools. The dog can smell with ease that there’s blood in the pool. Another example: 3 seconds in 100,000 years. Dogs smell like we see. We walk into a room and see the room; a dogs walks into the room and smells the room. We see a cut on our leg; the dog smells it. We have trained dogs to sniff gun powder, narcotics, missing persons, and now, finally, diseases. The interesting part about this is that cancer absolutely has a smell. Most oncologists will tell you that humans can actually smell cancer in latter stages through the patients breath. If we can smell it at stage 3-4, then of course a dog would be able to detect the scent much earlier, in stage 0, 1 or 2. There are many published studies that prove dogs can detect cancer through breath samples, and scientists and doctors are trying to come up with a breathalyzer test that works as good as the dogs nose. So far, the only ones that can smell cancer in early stages, are the dogs.

Training dogs to smell cancer is done in the same way that bomb and narcotics dogs are trained, pairing the target odor with a high value reward. (Kind of like the dog smelling the sick bird, and then getting to eat it). With breath, however, things can get a little tricky. Remember, drugs and gun powder can be isolated, but 
“cancer scent” is one of the thousands of organic compounds within a humans breath. In order for the dogs to generalize the “cancer scent”, many samples with the common odor must be used. Also, the dogs must be trained to ignore healthy breath, and all other breath with diseases other than cancer. This means samples. LOTS of samples to use for the dogs training. Cancer samples, disease controls and healthy controls are needed, and the order and specifics of the introduction of cancer through latter stage training is extremely specific, in order for the dog to generalize the cancer scent. Right now, the important thing to remember is that dogs can smell cancer. They have good reason to, and it can save your life.


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