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Can Dogs Smell Cancer in Humans? Vet-Reviewed Facts & FAQ

dog sniffing sick woman wearing a mask

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Dr. Lorna Whittemore Photo

Reviewed & Fact-Checked By

Dr. Lorna Whittemore

Veterinarian, MRCVS

The information is current and up-to-date in accordance with the latest veterinarian research.

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It’s been thought for centuries now that dogs can smell illnesses, diseases, and even coming storms that we can’t. However, there have also always been rumors that those are just old wives’ tales. Dogs have a very keen sense of smell, so it’s no surprise that they can sniff out things that we can’t.

So, can dogs smell cancer? Yes, it is thought that dogs can sniff out and detect cancer in humans, according to a study published in 20061. How do they sniff cancer out? We’ll answer these questions and more below.

divider-dog paw

Can Dogs Sniff Out Cancer?

Studies have shown that dogs can sniff out certain types of cancer in humans. Cancer, like other diseases, can leave odor signatures on a person’s body. There is evidence that VOC (volatile organic compounds) are produced by certain diseases and that dogs can smell these.

Depending on the type of cancer the person has, a trained bio-detection dog can detect VOC when exposed to these:

  • Breath
  • Skin
  • Urine
  • Feces
  • Sweat

Dogs have been known to detect these smells, and if the dog has been trained to do so, it can alert the person that there is a problem.

What Type of Cancer Can a Dog Detect?

While all types they can smell are still being researched, dogs can smell the following cancers with greater accuracy.

  • Malignant melanoma
  • Colorectal cancer
  • Lung cancer
  • Ovarian cancer
  • Prostate cancer
  • Breast cancer
  • Bladder cancer
dog sniffing owner's hands
Image Credit: Prostock-studio, Shutterstock

How Can Dogs Smell Cancer?

Tumors produce VOC and these are released into the breath, sweat, urine and feces. It is thought that the dog’s sensitivity to these smells lets them smell cancer in some people or samples in a laboratory setting. There is also work being done into the theory that they can smell a change in a person’s gastrointestinal biome (natural bacteria) that seems to be involved in cancer.

While cancer-detecting studies have shown promising results, dogs can’t sniff out cancer in patients with 100% accuracy. So, don’t be ready to give up medical testing in favor of a canine’s nose just yet.

divider-pawWhat Other Things Can Dogs Smell?

Dogs have a very keen sense of smell, over 10,000 times better than humans and they can easily smell things that we can’t. But can dogs smell other diseases? Yes, they can.

1. Oncoming Seizures

Medical Alert Assistance Dogs can be trained to sense when their owners have a seizure coming on. The dogs can detect a change in their owner’s scent up to 45 minutes before a seizure occurs and alert them so that they can be safe.

2. Bacteria

Dogs can be trained to smell specific types of worrying bacteria and ignore those that are beneficial. In the future, it is hoped that this will help detect serious bacterial infections early and reduce antibiotic resistance.

golden labrador dog sniffing person hands in snowy winter park
Image Credit Bogdan Sonjachnyj, Shutterstock

3. Diabetes

Specially trained dogs can alert their human companion to dangerous changes in blood glucose and even get help for the person or bring them their medications. These service dogs improve quality of life and health for their lucky humans.

4. Malaria

Scientists are always looking for reliable, fast, cheap and easy ways of providing good healthcare. Malaria is a devastating illness spread by mosquitoes, especially in large parts of Africa. Recent and ongoing work has shown that dogs can be trained to smell malaria-infected socks with a promising accuracy of 73%.

Brown dog sniffing a man sitting outside


Final Thoughts

While dogs can smell cancer in humans, it’s still essential to have medical testing done if you’re suffering from an illness. Canines can detect several types of cancer, but not with 100% accuracy. There is still a lot to be learned and improved when training dogs to detect cancer, but strides are being made in this exciting research every day.

Featured Image Credit: rfranca, Shutterstock

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