Can Dogs Really Smell Cancer in Humans?

By Becky Casale, creator of The Complete Guide to Shelties and Mindful Shelties Coloring Book. Sheltie Planet earns commissions from the sale of Amazon products at no extra cost to you.

Dogs can smell cancer in their owners and even alert them to it. In one study, a Labrador-Spaniel cross named Lucy even a achieved a 95% success rate.

Meet Daisy. She's a Labrador who detected breast cancer in her owner.

"She kept staring at me and lunging into my chest... It led me to find a lump." - Claire Guest

Daisy the Labrador detected breast cancer in her owner Claire Guest

Claire Guest and her Labrador, Daisy.

Claire 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. She's been trained to sniff out bladder, kidney, and prostate cancer. She has a 95% success rate—better than some lab tests used to diagnose cancer.

In Germany, this scent detection experiment involved training four dogs (two German Shepherds, a Labrador Retriever, and an Australian Shepherd) to smell breath samples from glass tubes and indicate the cancerous ones.

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

The exhaled breath of patients could be the ideal way to screen for lung cancer in future. However, current technologies based on signal pattern analysis are no use because they don't know what molecular targets to look for. But dogs do.

German Shepherds can smell lung cancer in breath samples.

Lung cancer is the most deadly of all cancers in the US, killing more people than prostate, breast, ovarian, lymph, and colon cancers combined. As always, early diagnosis is critical to improving survival rates.

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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 can smell cancer because they have 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.

Which Dog Breeds Have The Best Sense of Smell?

Not all dogs have an equally powerful sense of smell. Due to their working dog history and selective breeding, Bloodhounds have have the most scent receptors, giving them the best scent detection ability.

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

Bloodhound
Basset Hound
Beagle
German Shepherd
Labrador Retriever
Belgian Malinois
English Springer Spaniel
Coonhound
German Shorthaired Pointer
Pointer

Will My Next Doctor Be a Dog?

Sadly, no! It takes a lot of training 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, this incredible talent is still being put to good use in cutting-edge cancer research. Future studies could help scientists identify specific organic compounds linked with cancers. It would speed up the creation of better diagnostic tools and save many more lives through early detection.

By Becky Casale, creator of The Complete Guide to Shelties and Mindful Shelties Coloring Book. Sheltie Planet earns commissions from the sale of Amazon products at no extra cost to you.