Sheltie Planet

Can Dogs Really Smell Cancer in Humans?


By Rebecca Turner

Astonishingly, it has been proven that dogs can pick up on the scent of cancer in humans. Now, certain breeds with the best sense of smell are being trained to detect cancer in patient samples with up to 95% success.

Meet Daisy - a Labrador who detected breast cancer in her owner, Claire Guest, six years ago: "She kept staring at me and lunging into my chest. It led me to find a lump."

Daisy Detected Breast Cancer in Her Owner Claire Guest

Daisy Detected Breast Cancer in Her Owner Claire Guest

Guest is now the CEO of Medical Detection Dogs in the UK. MDD is part of one of the largest clinical trials of dog cancer detection. So far they've had eight dogs sniff out 3,000 urine samples to see if they could detect the presence of cancer.

Another of MDD's canine members is a Labrador-Spaniel cross named Lucy. Despite flunking out of guide dog school, she has since been trained to sniff out bladder, kidney and prostate cancer. She has a 95% success rate - that's better than some lab tests used to diagnose cancer.

An earlier experiment in Germany saw scientists training four dogs (two German Shepherds, a Labrador Retriever and an Australian Shepherd) to smell breath samples from glass tubes and indicate which were the cancerous ones.

German Shepherd Dogs Can Smell Lung Cancer in Breath Samples

German Shepherd Dogs Can Smell Lung Cancer in Breath Samples

The dogs correctly identified 71 out of 100 (71%) of the lung cancer patients, and 372 out of 400 (93%) who were perfectly healthy.

Lung cancer is the most deadly of all cancers in the US, killing more people than prostate, breast, ovarian, lymph and colon cancers combined.

How Do Dogs Smell Cancer?

While humans primarily rely on vision to interpret the world, dogs heavily rely on their sense of smell. Their noses contain millions more scent-detecting cells than people, with a dense folding membrane of scent cells and nerves.

In humans, this folded scent organ is about the size of a postage stamp. In dogs, it's almost the size of an A4 sheet of paper!

Dogs Smell Cancer By Having Millions More Scent Detecting Cells Than Humans

Dogs Smell Cancer By Having Millions More Scent Detecting Cells Than Humans

Dogs also dedicate more brain power to interpreting smells - about 40 times as much as people. This gives them the amazing ability to detect smells on an infinitesimal level.

But not all dogs are created equal. Bloodhounds have the best ability to detect smells since they have the most scent receptors of all canines.

Here are the top 10 dog breed with the best sense of smell:

  1. Bloodhound
  2. Basset Hound
  3. Beagle
  4. German Shepherd
  5. Labrador Retriever
  6. Belgian Malinois
  7. English Springer Spaniel
  8. Coonhound
  9. German Shorthaired Pointer
  10. Pointer

Will My Next Doctor Be a Dog?

Sadly, no!

It takes a lot of training (compared to established lab tests) to teach a dog to report when they can smell cancer. What's more, the capacity for trained dogs to smell cancer isn't 100% foolproof. So we probably won't see dogs at the front line of cancer diagnosis.

However, their incredible talent is still being put to good use in cutting-edge cancer research. For example, future studies could help scientists identify the organic compound linked with lung cancer. This would speed up the creation of better diagnostic tools and save many more lives through early detection.

Here's to man's best friend!

About The Author

Rebecca Turner is the creator of Sheltie Planet where she writes about her love of Shetland Sheepdogs, inspired by her two Shelties, Howard and Piper. Learn more about Rebecca. Chat with our online Sheltie community on Facebook, Twitter and our Sheltie Forum.