15 Fascinating Things Dogs Can Smell That Humans Can’t

No matter the breed, all dogs are incredible sniffing machines, and we depend on their sense of smell in a variety of ways that benefit humans.

Humans interpret much of the world through sight, but for a dog, it’s their instinctual sense of smell that helps them survive. Studies have shown that a dog’s nose has between 125 to 300 million olfactory receptors compared to the human nose with only 5 to 6 million receptors. With a sense of smell 40 to 50 times stronger than humans, is it any wonder why we rely on the canine’s superpowers to sniff out drugs, diseases and missing persons?

The canine nose is built to interpret odors, and all it takes is one sniff to get the detailed information they need to analyze a situation. For instance, a dog can tell if you’re male or female, if you’ve been around other animals, what you’re feeling and even areas you’ve recently visited. This is possible because a dog’s nasal cavity has an intricate olfactory system with unique nerve cells that connect directly to the brain and help detect all types of odors, including those that are undetectable to humans.

Other Key Reasons That Dogs Can Smell Better

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Another reason dogs can smell better than humans is how we use our noses. Humans breathe and smell through the same air passage, whereas a dog’s nose has a fold of tissue inside that separates breathing and smelling. Their noses extend from the nostrils to the back of the throat, enabling them to sniff things more intensely than we can.

But not all breeds are created equal on the sniff scale. Dogs with shorter noses have less space for the nerve cells that detect senses than canines with longer snouts. For example, a pug’s nose has fewer sensors than a bloodhound. No matter the breed, all dogs are incredible sniffing machines, though, and we depend on their help in a variety of ways that benefit our lives. Here are 15 things dogs can smell that humans can’t and what it means.

15. Missing Persons

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Search and Rescue (SAR) dogs are trained to follow specific scents to locate missing persons such as lost children, elderly people who have accidentally wandered off and hikers lost in the woods.

Cadaver dogs are used to find victims of homicide, accidents or natural disasters.

How Dogs Use Smell to Find Missing Persons

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These air-scenting canines are trained to follow airborne microscopic particle scents emitted from humans. They’re able to discriminate the smell of a single human, whether that person is in a crowded area, out in the woods, under piles of debris or even beneath several feet of water.

Many lives have been saved due to the extraordinary abilities of an SAR dog’s nose.

14. COVID and Other Diseases

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Trained canines have become an essential tool in detecting COVID-19 positive individuals, including asymptomatic people.

People are screened by a dog’s keen sense of smell before getting on an airplane or attending events such as concerts or sports in large arenas.

How Dogs Use Smell to Detect COVID

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Scientists believe that humans release volatile organic compounds (VOCs) when ill and that, when these molecules evaporate, an odor is left on the body that only canines can smell.

During the height of the pandemic, the Miami Heat basketball team used dogs to screen fans before games, and the results of detecting the virus were incredibly accurate.

13. Illegal Drugs and Explosives

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Detection dogs use their superior sense of smell to sniff out illegal drugs, explosives and all sorts of contraband. Narcotic Detection Dogs are sensitive to the scent of drugs and can even pick up the slightest trace of drug residue.

The Explosive Detection Canines, known as “bomb dogs,” are also trained similarly to detect specific chemical vapors from explosives.

How Dogs Use Smell to Find Illegal Drugs and Explosives

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A Pavlov style of repetition and reward is used to locate the target scent. Drug-sniffing dogs alert the presence of contraband by pawing or digging at the spot. The bomb dogs use a more passive approach by sitting down in front of the area where explosives are found.

Whether conducted indoors or outdoors, using sniffer dogs ensures our safety at airports, schools, hospitals, businesses, homes, boats and vehicles.

12. Cancer

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Like the dogs trained to sniff out COVID, canines used to find cancer are conditioned to identify the distinct smell of certain diseases.

Bodily fluids such as sweat, saliva, urine and blood are used as samples to train dogs in determining the biological compounds of cancer found in humans.

How Dogs Use Smell to Detect Cancer

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One study with dogs proved 97 percent accuracy in detecting cancer.

These promising results may lead to a new, non-invasive and inexpensive way to do screenings, and with early detection, these canines could save thousands of lives.

11. Hunting Prey

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Dogs have been used for hunting prey for thousands of years. They are born with predatory instincts that enable them to sniff out and chase their target.

Some breeds are better hunters than others — retrievers, pointers, spaniels, setters and hounds make the best trackers.

How Dogs Use Smell to Hunt Prey

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Training involves plenty of practice with positive reinforcement to hone their skills. These canines rely heavily on their noses, tracking game by following the scent on the ground or by sniffing the air for cues. They’re also trained to ignore all other smells around them to focus solely on their target.

Detection dogs have been successfully used to identify wildlife scat, including owls, small rodents, salamanders and even whale poop that is 1.6 miles away. Hunting dogs were essential to early man’s survival and, to this day, are widely used by hunters in the wilderness.

10. Epilepsy

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Seizure Alert dogs are trained to recognize an oncoming seizure anywhere between 15 minutes to 12 hours before the episode occurs.

Scientists believe that humans give off a different scent before a seizure that a dog can somehow smell.

How Dogs Use Smell to Detect Epilepsy

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Positive reinforcement with click-and-treat training methods is most effective in teaching a dog how to alert its partner and avoid injuries caused by seizures. These canines are also trained to alert caretakers, fetch medications, cellphones and even open doors for emergency personnel.

Sevice dogs are invaluable to giving people with disabilities more independence, confidence and peace of mind.

9. Criminals

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Whenever a human touches something or sits somewhere, they leave their individual scent on that surface.

Dogs can find fugitives on the run or determine if a criminal was present at a crime scene using their noses to sniff out scents collected by forensic experts.

How Dogs Use Smell to Find Criminals

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In the canine training process, scent samples are used (such as DNA, hair, a fingerprint or body odor) to determine the target. The dog sticks their nose in a jar containing a specific aroma and then sits in front of the jar with the correct scent.

The proof of a dog’s sniffer is hard to beat in court once they prove a criminal’s identity. This method often leads to the criminal’s confession and conviction.

8. Bed Bugs

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Dogs can detect a specific odor that bed bugs produce from their scent glands at the earliest development stages.

With a reported 96 percent accuracy in detecting the invasive bugs, some pest control companies use canines to sniff them out.

How Dogs Use Smell to Find Bed Bugs

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A dog’s highly sensitive snout quickly smells the odor that we cannot detect from bed bugs.

This remarkable ability has prevented many a homeowner from an infestation.

7. Pregnancy and Ovulation

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A dog’s nose is sensitive to the smell of urine in both animals and humans. When ovulation or pregnancy occurs, hormonal changes in the body can affect the urine’s scent, and a canine can tell the difference.

No matter how slight the hormonal shift is, a dog can detect pregnancy in its early stages, often before a woman has taken a pregnancy test.

How Dogs Use Smell to Detect Pregnancy and Ovulation

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Although there is no definitive proof of a dog’s ability to sniff out ovulation, they’re attracted to a female’s scent when the hormonal levels have changed and will sniff the crotch area more frequently.

For this reason, farmers have used dogs to sniff cow urine to determine if the animal is in heat and ready for artificial insemination. Another benefit of dogs sniffing urine is the possibility of detecting ovarian cancer, which could save a patient’s life if caught in the early stages.

6. Arson

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Known as Accelerant Detection Canines (ADC), these dogs are used by law enforcement and firefighters to detect possible accelerants used at the fire scene.

A dog can cover an arson scene in 30 minutes versus the months it can take in a crime lab to retrieve the same results.

How Dogs Use Smell to Detect Arson

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Training for this job requires multiple drills several times a day. Once a flammable liquid is pinpointed, the dog alerts the handler and is rewarded with high praise and food. The canines are also trained to mingle among the spectators at the fire scene to sniff out a possible arsonist.

This speeds up the process of finding the suspect and getting higher conviction rates. With the ADC’s successful track record of confirming accelerants’ presence (or eliminating the possibility if none are located), insurance companies can expedite the claims process.

5. Cyber-Criminal Activity

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The use of Electronic Storage Detection (ESD) dogs is relatively new but has proven to be successful in finding child pornography and other cyber-criminal activity.

The canines are trained to detect two different scents from electronics — one from circuit boards of storage devices and another from DVDs, floppy disks and CDs.

How Dogs Use Smell to Find Cyber-Criminal Activity

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Dogs can also sniff out more minor things like SD cards or thumb drives and even locate electronics when turned off.

If you lose your cellphone in the wilderness, an ESD dog can find that, too!

4. Diabetes

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With one sniff of a human’s breath, a Diabetes Assistance (DA) dog can determine a change in blood sugar levels.

When the glucose levels drop, it alters the way our breath smells, and DA dogs can pick up that scent.

How Dogs Use Smell to Detect Diabetes

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Early detection is critical for people with severe diabetic conditions — it helps them avoid a blood sugar emergency when the levels drop too low.

These amazing dogs are trained to alert their owner by pawing them or nudging them with their nose and saving their owners from dangerous diabetic episodes.

3. Human Emotions

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Just as dogs detect hormonal changes in women during ovulation and pregnancy, they can also smell a shift in our body chemistry when our mood changes.

Whether it’s stress hormones or happy hormones, a dog knows what we’re feeling by sniffing our breath or our sweat.

How Dogs Use Smell to Detect Human Emotions

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There’s no training required; dogs are instinctively sensitive to our emotions and will stay close by as if to offer support whenever we are feeling anxious, sad, ill or frightened.

In some ways, canines know us better than we know ourselves!

2. Natural Disasters

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Studies have shown that dogs are born with sensory cells at the end of their noses that allow them to detect changes in the atmosphere.

Whether from their superior olfactory senses or a unique canine sixth sense, dogs can predict when natural disasters are about to occur — including a heatwave, tornado, earthquake, snowstorm, hurricane or flooding.

How Dogs Use Smell to Detect Natural Disasters

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In other words, dogs can sense impending doom long before humans have a clue.

The numerous tales of dogs saving people from natural disasters have earned them their well-deserved heroic legacy.

1. Their Owners

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A blindfolded dog can walk into a room full of people and, without a sound, find its owner with a brief sniff.

Canines have “sniff recognition,” which means that their owner’s distinct scent is linked to positive memories, such as playing, affection, food, praise and security.

How Dogs Use Smell to Find Their Owners

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These activities create a bond between a dog and its owner, and the comforting smells associated with this attachment are calming.

A dog shows love for his family by tail wagging, head tilting, alertness, nuzzling, staring and happy barks. Is it any wonder that these fantastic creatures are man’s (and woman’s) best friend?