Can Dogs Smell Cancer? Yes, and These 5 Other Diseases

Have you ever wondered why a dog stops to sniff everything in its path? Dogs use their noses to “see” the world and make sense of it. That’s why dogs sniff one another upon greeting instead of shaking paws.

Dogs’ powerful sense of smell is also why many canines do well in search and rescue, security, bomb and fire accelerant detection, and other essential jobs.

Growing research suggests that canine companions can also use smell to detect human diseases. Dogs are so effective at noticing a change in a human scent that many can sniff out signs of disease that even medical tests cannot pick up.

Can dogs smell cancer?

Yes, it’s believed that dogs’ incredible sense of smell makes it possible for them to sniff out cancer. Researchers have been studying dogs’ potential ability to identify complex chemical compounds in human breath, urine, and sweat. By doing so, dogs may be able to detect cancer (and other diseases).

A review of several studies on canine scent detection and cancer indicated that dogs might be able to identify the following cancers from human scents:

• Lung cancer through a person’s breath

• Bladder cancer by sniffing a person’s urine

• Breast cancer by sniffing a person’s breath

• Prostate cancer by smelling a person’s urine

• Skin cancer by sniffing a person’s skin

• Ovarian cancer by smelling blood samples

But more research is needed to confirm that dogs can detect cancer, not just other signs of illness. For example, it could be that dogs are able to smell inflammation or tissue death that are signs of cancer, rather than the cancer itself.

Can untrained dogs smell cancer?

There have been some personal accounts of untrained dogs detecting cancer. But dogs usually need to be trained to detect and then respond when they smell cancer in humans. They don’t have a natural ability to do this without training.

Which dog breeds are best at detecting cancer and other diseases?

There isn’t a lot of research on which dogs can smell cancer the best. There are different things that can affect a dog’s sense of smell besides their breed, including their age or the anatomy of their nose. But Labradors and shepherds breeds have been used as sniffer dogs for their high sense of smell and motivation.

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When else are dogs used to detect diseases?

In addition to cancer, some dogs are being trained to recognize signs of the following five conditions.

1. Diabetes

Thanks to their ability to detect changes in blood sugar, diabetes alert dogs are well-known service animals. These specially trained dogs can detect when blood sugar levels are too high or too low in people with diabetes.

But research suggests not all dogs are equally effective at detecting unusual blood sugar levels. It varies depending on the person and their dog.

2. Migraines

Dogs seem to be able to detect oncoming migraines in people, largely thanks to their sense of smell. Migraine service dog trainers believe dogs can detect migraines thanks to changes in the smell of a human’s breath before the onset of an attack.

There is some evidence that dogs can detect migraines even if they aren’t trained service dogs. People surveyed also reported that they noticed a change in their dog’s behavior before they got a migraine. But this hasn’t been verified through formal research.

3. Seizures

Some dogs may be able to predict seizures in humans, but it’s not clear that dogs are particularly good at it. Research suggests that dogs can recognize seizures based on the smell associated with seizures. But not all dogs seem to be able to predict a seizure before it happens. In fact, the Epilepsy Foundation says that dogs who can predict human seizures are rare.

4. Parkinson’s disease

More research is needed, but there is some evidence that dogs may be able to sniff out Parkinson’s disease. Researchers pursued this theory after determining that people with Parkinson’s disease seem to have a distinct smell.

So far, dog trainers from Washington state and researchers in China have shown that dogs can learn to identify Parkinson’s disease. In some experiments, researchers believe dogs can accurately detect Parkison’s disease about 90% of the time.

5. COVID-19

Several research studies suggest that dogs can accurately determine who has COVID-19. In some cases, dogs trained to detect COVID-19 were accurate 92% of the time.

The accuracy of COVID-19 detection varies, though. Two dogs trained to sniff out COVID-19 in San Francisco, for example, were correct about 80% of the time. And in some cases, these two dogs were able to tell someone had COVID-19 before they tested positive using an antigen test.

How can dogs smell disease?

Dogs detect changes in scent. The human body contains a complex mixture of chemicals that gives off a smell. One-eighth of a dog’s brain is dedicated to understanding scent. Additionally, dogs inhale about 300 times per minute, constantly supplying new odor particles to the cells responsible for scent.

As any dog owner can tell you, dogs know a person’s smell. A 2011 research study supports this. Dogs could tell identical twins apart by smell, even if they lived in the same home and ate the same diet. So what the dogs pick up on is a change in odor.

Illness changes a person’s scent. For example, cancerous cells produce chemicals that have a distinct odor. Even in the early stages of a disease, chemicals are:

• Released into a person’s urine

• Exhaled in the breath

• Released through sweat

Dogs are skilled at detecting these types of changes in scent.

How do dogs act if they smell cancer or other illnesses?

When dogs smell illness, their behavior can change. But most often, dogs need to be trained to respond in a specific way that something is off. Some dogs are trained as official service animals for particular conditions. Other dogs are trained as part of research studies.

Trained disease detection or service dogs may:

• Touch, lick, or poke their nose at certain body parts

• Retrieve dropped items, such as a phone

• Wake their owner if they sense the owner’s blood sugar is too high or too low

• Help provide balance for someone with a neurological disorder

• Signal certain sounds for deaf owners

• Nudge someone away from danger

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Written by:

Lauren Lee, BA, MA

Lauren Lee, BA, MA, is a writer specializing in animal care and pet health content. Since she was a young child, her passions have been writing and anything to do with animals.

Edited by:

Renée Fabian, MA

Renée Fabian is the senior pet health editor at GoodRx. She’s worked for nearly 10 years as a journalist and editor across a wide range of health and well-being topics.

Reviewed by:

Ghanasyam Bey, DVM

Ghanasyam Bey, DVM, is from Cleveland, Ohio, and attended Princeton University for undergraduate studies. After a year of biology research at Duke University, he attended Ohio State College of Veterinary Medicine.

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