How Do Dogs Act When They Smell Illness?

Last Updated: January 28, 2024
Dogs Acts like it  Smell Illness

Dogs are known worldwide for their strong sense of smell. We see examples of it all the time in movies and cartoons.

It's one of the staple characteristics that everyone knows about canines, and their powerful olfactory senses make dogs capable of doing far more than humans can. That's why we see dogs doing risky jobs like search and rescue missions, bomb detection and drug sniffing.

But did you know that dogs can smell illness and disease? 

Believe it or not, canines can sense the minuscule changes in our body chemistry whenever we fight viruses, bacteria, and other invaders that put our health at risk. Not only do they sense those changes, but they often respond to them in weird ways!

About the Canine Olfactory Senses

Everyone knows that dogs have an unbeatable sense of smell. If you're a dog owner, you know there's no hiding snacks or treats! But where does this unique ability come from?

It turns out that your furry friend is built for sniffing!

Canines have an estimated 220 million scent receptors. To put things into perspective, humans have a mere 5 million! A dog's sense of smell can be up to 100,000 times stronger than yours. They detect the tiniest substances in parts per trillion, making their smelling capabilities far beyond what humans can do.

That's not all. Dogs smell a little differently than we do, too.

When dogs sniff, about 12 percent of the air they take in goes into the olfactory region. The rest goes to the lungs for breathing.

That 12 percent of the air moving into the olfactory system carries molecules of various substances. Those molecules meet the millions of scent receptors in the nasal cavity, delivering a world of information with one sniff!

That's why dogs go crazy over smells that we find gross. What you see as a nasty garbage bag is a whirlwind of information for your dog. Imagine what types of molecules they pick up from sniffing garbage or poking their nose around a pile of leaves!

Dogs can sniff up to 300 times per minute and usually take in scent with their right nostril. If they enjoy or recognize the smell, they switch over to the left nostril to keep smelling it. Meanwhile, the right nostril stays on the lookout.

This unique biological hack comes down to their wild ancestors. Wild canines have no choice but to stay alert to remain safe. So even when they enjoy the scents before them, that right nostril is constantly sniffing for potential predators.

Why Can Dogs Smell Illnesses?

Dog laying on owner as if it setect something

Experts also believe that the ability to smell illnesses is a byproduct of survival instincts from the past. 

Your pup's earliest ancestors had a significantly tougher way of life. They had to hunt and scavenge to stay alive.

It wasn't uncommon that they'd hunt down an ill animal or come across a diseased carcass. Eating those diseased prey animals could put their own health at risk. Thus, they developed the ability to sense illness. It was all a matter of adaptation and survival.

Some also theorize that wild dogs used their ability to smell diseases to protect the pack. 

For example, they could sense when one of their own was on the verge of death due to illness. When that happened, they often took the sick dog out of their misery to prevent whatever ailment they had from spreading to the rest of the pack.

What Exactly Do Dogs Detect When They Smell Disease?

When you're suffering from a bacterial infection, virus or even life-threatening disease, you possess a certain smell. Even small biological changes produce a scent.

However, those molecules are so tiny and sporadic that diseases don't produce any smell that's negligible to humans. We're simply unable to detect that type of thing with our noses.

But dogs are special. Those 220 million scent receptors work magic to pick up even the tiniest molecules. When a dog senses a disease, it detects the small changes in the body chemistry that are happening within the body. They can also pick up chemicals that are undetectable to humans.

For example, many diseases produce volatile organic compounds. Cancer cells produce these compounds, allowing dogs to know a person has cancer before they even realizing it.

It's an interesting biological quirk, and it's just one of many reasons why dogs are so special. That innate ability to detect the tiniest chemicals and compounds allows canines to achieve feats that are so incomprehensible to us.

It's the same way they can detect hidden drugs or explosives. The ability also allows canines to find missing persons, making them excellent rescue companions.

What Types of Illnesses Can Dogs Sniff Out?

You'd be surprised by just how much dogs can detect.

Many researchers and healthcare professionals are employing dogs to take advantage of their strong sense of smell. Trainers can work with dogs to fine-tune their disease-detection capabilities in the same way that trainers prepare dogs to accompany police officers or help those with disabilities.

Disease-smelling dogs are often called bio-detection dogs, and trainers can help pups hone in on a specific disease. Dogs can smell all types of illnesses. However, targeted training can make pups even more capable and useful in real-world settings.

So, what diseases can dogs smell?

Cancer is a great example! Trainers and researchers continue to work with dogs, coaching them to smell cancer in urine, feces, sweat and blood. As mentioned, dogs typically detect volatile organic compounds produced by cancer cells.

Some dogs even smell cancer through a person's breath. Even more impressive, dogs can successfully smell cancer across all four stages of the disease.

As you can imagine, this capability can be life-changing. Early detection of cancer is paramount, and many people don't realize that they have the disease until a bio-detection dog lets them know.

Cancer is not the only thing dogs can smell. They can also detect diseases like Malaria and Parkinson's disease. During the global COVID-19 pandemic, trainers could teach bio-detection dogs to detect coronavirus!

Bio-detection dogs have a bigger presence in the healthcare industry than ever before. But they also use their strong sense of smell to help people in their homes. Many doctors recommend that people with diabetes adopt a medical alert dog.

People with diabetes can experience sudden blood sugar drops with zero warning. Low glucose levels can cause seizures, loss of consciousness and other dangerous issues.

Medical alert dogs have the ability to smell blood sugar levels through an owner's breath. With proper training, they'll detect those glucose changes and alert their owners to take action.

Many medical alert dogs have used their ability to smell body chemistry changes and diseases to save lives!

Do Dogs Need Training to Detect Diseases?

Dog sniffing with its nose to detect disease

Here's the thing about disease detection: All dogs can do it. Dogs all have impressively strong senses of smell that surpass a human's. Therefore, dogs can often sense diseases in owners with zero training.

There are countless stories about dog owners noting their pup's odd behavior only to find out later that they have cancer or some other illness!

Training can help canines fine-tune their senses. It teaches them what to do when they smell a disease. But any dog can sense illness.

Signs That a Dog Smells an Illness

So, how do dogs act when they smell illnesses?

It all depends on the dog and whether or not they have training.

Generally, medical alert and bio-detection dogs learn to provide clear signals when they smell disease. For example, they might bark, paw at their handler or nudge them with their nose.

Whatever they're taught is how they react, and handlers typically know to look for those behaviors as a sign that the dog senses something.

Dogs that don't receive any formal training can act oddly. The smell of a disease is something new for dogs, so many will be unpredictable.

The most common response is to raise their nose and tilt their head. It's similar to what your dog would do when smelling or hearing something that piques their interest.

Some dogs will look alert. They won't go crazy, but they'll remain on high alert because they know that something is there that shouldn't.

So, you might see your dog looking around calmy or pacing as they try to figure out what's going on. You may even see your pup's tail rise without wagging, indicating that they detect something.

Many pups remain calm when they smell disease. 

They don't necessarily know what they smell, but they know that it's not good. It's common for pups to go into protective mode. Therefore, they might stand by your side because they feel that something is trying to harm you.

Conversely, some dogs freak out.

It's when they go a little crazy that many owners realize something is up. Your dog might stare at you and begin barking. Some will whine incessantly and try to lick you as if they're soothing an invisible wound.

A Final Word

A dog's ability to smell illnesses is a fascinating and often misunderstood trait. Your furry friend's biology is unique, and their signature powerhouse nose can detect more than you realize.

If your dog starts exhibiting strange behaviors like the ones we mentioned above, consider taking a trip to the doctor. Of course, you should never rely on your dog alone for disease detection.

But your canine companion loves you. So when it smells something emanating from your body that you can't see, don't be surprised when it tries to let you know!

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