Can Dogs Smell Cancer?

Dogs Can Learn To Smell Disease

A dog's nose

Can man’s best friend also be a person’s best chance for early cancer detection? Some studies say yes.

Dogs have long been associated with heroic acts. They dutifully lead the disabled. Their ability to identify chemicals diluted as low as parts per trillion allows them to pick up where the human nose leaves off. So why not detect cancer?

Doggie Detectives

Studies have indicated that dogs can successfully identify bladder and melanoma cancers in sufferers. But researchers of a 2006 study at Pine Street Foundation in Marin County, Calif., led by Michael McCulloch, got some impressive results. They found that dogs could positively identify breast and lung cancer with 99 percent accuracy.

Just Breath

Here’s how the study was carried out:

Golden retriever

Five dogs (three Labradors and two Portuguese water dogs) were borrowed from owners and Guide Dogs for the Blind. They were trained over a three week period to detect lung and breast cancer based on nothing but breathe.

All 86 cancer patients, smokers and non-smokers, had recently been diagnosed with cancer and had not yet undergone treatment. Then, 83 healthy volunteers were mixed into the group. Each person gave breathe samples that were captured in tubes and presented to dogs individually.

Dogs would sit or lay down in front of the samples when they detected cancerous scents. They were trained to ignore negative samples. Dogs were rewarded with a clicker and food rewards.

Researchers found that dogs could accurately spot cancer from very early to late stages.


A dog’s sense of smell is on average 10,000 to 100,000 times superior to that of humans.

The Next Phase

The same clinic is studying which chemicals in cancerous breath dogs are reacting to. To assist in the process, Dr. McCulloch’s team developed a device that can acquire breath “fingerprints” designed to help identify markers for early cancer detection to help make that possible.

A clinical trial, which includes early detection of ovarian cancer, is also on the horizon.

A Strong Sense of Smell

A dog's nose

A dog’s sense of smell is on average 10,000 to 100,000 times superior to that of humans.

While it remains unclear what exactly makes dogs such good smellers, it is indisputable that much more of a dog’s brain is devoted to smell than it is in humans.

It is the cancer researchers’ hope that in the future dogs can help detect cancer from the comfort of a doctor’s office.


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