Dogs Detect Disease With Uncanny Accuracy

Written by Dr. Karen Shaw Becker

dogs smell disease

Story at-a-glance -

  • Dogs are so astute at detecting cancer that if your dog seems unusually obsessed with smelling a certain part of your body, your breath or a spot on your skin, it’s worth paying attention
  • Wisconsin resident Stephanie Herfel claims her Siberian Husky Sierra successfully alerted her to ovarian cancer — not one but three times
  • Sierra sniffed the woman’s lower belly intently and then hid, a behavior she exhibited three times, first when Herfel was diagnosed and two other times when the cancer recurred
  • In Situ Foundation is working on scientifically training dogs to detect early-stage cancer in humans and has partnered with the University of California, Davis to develop cancer detection dogs that will offer screenings to the public

Your dog’s nose is 10,000 to 100,000 times more sensitive than your own,1 which explains why he can smell things you can’t, like 1 teaspoon of sugar in two Olympic-sized pools of water and even things you might not associate with smell at all, like diseases, including cancer.2

Dogs are so astute at detecting cancer that if your dog seems unusually obsessed with smelling a certain part of your body, your breath or a spot on your skin, it’s worth paying attention. That’s what Wisconsin resident Stephanie Herfel did, and her Siberian Husky Sierra successfully alerted her to ovarian cancer — not one but three times.

Husky Hides at Smell of Cancer

The first time Sierra gave Herfel a clue that something was wrong, “She put her nose on my lower belly and sniffed so intently that I thought I spilled something on my clothes,” Herfel told the Milwaukee Journal Sentinel. “She did it a second and then a third time. After the third time, Sierra went and hid. I mean hid!"3

Herfel had been experiencing abdominal pain, but when she went to the emergency room, they said she had an ovarian cyst. Unnerved by Sierra’s reactions, Herfel decided to make an appointment with a gynecologist, who ultimately discovered that she had cancer. After surgery and chemotherapy, Herfel went into remission, but in 2015 and 2016 the cancer returned. Both times, Sierra had exhibited the same response, becoming afraid and hiding.

Even more striking, Sierra also had the same reaction when a friend with ovarian cancer came to visit. And she did it one other time when a worker doing a remodeling job on their home came over. Herfel is so convinced of Sierra’s ability to detect cancer that she called the worker’s boss to tell him. The Milwaukee Journal Sentinel continued:4

“Her primary oncologist, David Kushner, told her Sierra's ability was not a fluke or a lucky guess. There have been other dogs of various breeds with this extraordinary skill, and their accuracy rate is 98 [percent] and applies to a number of cancer types.”

Dogs May Detect Cancer as Well as Standard Diagnostic Procedures

It was 1989 when researchers first published a case report of a dog who sniffed a lesion on his owner’s thigh, and the lesion turned out to be melanoma.5 In 2004, a study was published showing that dogs could be trained to pick out bladder cancer from urine odor alone.6

While dogs still aren’t routinely used to sniff out cancers in medical settings, perhaps they should be. In the case of colorectal cancer, a 2011 study found that a specific cancer scent does exist in both breath and fecal samples, and dogs were able to detect the scent with an accuracy level comparable to colonoscopy. The dogs were able to accurately detect cancer even in cases of early-stage disease.7

Yet another study found dogs detected ovarian cancer via blood samples not only at the time of first diagnosis but also three and six months later at the time of recurrences.8 Further, dogs specially trained to sniff out cancer from breath samples can then detect cancer with more than 60 percent accuracy.9

Whether dogs will one day become a regular part of cancer detection remains to be seen, but electronic noses that attempt to sniff out diseases the way dogs do have already been created.10

“I absolutely believe that [dogs] can detect cancer,” Dr. Cynthia M. Otto, director of the University of Pennsylvania School of Veterinary Medicine (Penn Vet) Working Dog Center, told American Veterinarian. “The bigger question is how we will use them in the battle to fight cancer.”11

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Dogs Are Already Being Used to Screen People for Cancer

Already, the Austin Firefighters Association is partnering with CancerDogs to get firefighters, who are at increased risk for cancer, regular cancer screenings. As of January 2018, 30,000 firefighters have been tested as part of CancerDogs’ Firefighter Cancer Screening Trials.

Although the screening is considered experimental and not a replacement for standard medical care, the hope is that dogs can help the firefighters detect cancer earlier, leading to more successful treatment. Ultimately, it’s hoped that dogs may one day be able to detect cancer in the general public as well.

Already, so-called bio-detection dogs are being trained to provide diagnostic support for difficult-to-diagnose cancers such as prostate cancer, as well as to detect the odor of volatile chemicals in urine, fecal and skin swab samples that may correlate with different illnesses ranging from cancer to malaria to Parkinson’s disease.12

In Situ Foundation is also working on scientifically training dogs to detect early-stage cancer in humans and has partnered with the University of California, Davis to develop cancer detection dogs that will offer screenings to the public. Currently, doctors only use three senses (hearing, sight and touch) to diagnose cancer. With the help of dogs, we can add a fourth sense, olfaction, to improve diagnosis. In Situ added:13

“Dogs have a high sensitivity and specificity, which means that dogs do not give the high false positive rates that modern day screenings give. False positives cause unnecessary biopsies, treatment, and worry.

In 2006, our study which was published in the Journal of Integrative Cancer Therapies,14 a medical journal, our dogs were proven at 99 [percent] sensitivity in the early detection of lung cancer, and 88 [percent] sensitive in the early detection of breast cancer. This is more accurate than a needle biopsy.”

Although dogs seem to be a promising tool to detect cancer in its early stages, there are legal and ethical considerations, not to mention scientific ones, before the process would become widespread. However, the number of anecdotal reports from dog owners who say their pets detected cancer is growing, so if your dog keeps sniffing you, it may be worth a trip to your doctor, especially if it’s a new behavior and there’s also a lump or lesion in the area.