A Trusted Friend in a Complicated World

10 Things Dogs Can Smell That Humans Can’t

Dogs are truly heroes—not that you needed any convincing.

Nose of a pointer
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Smelling is part of a dog’s natural behavior, both instinctually for survival and to make sense of the world around them. A typical dog’s nose contains 300 million olfactory receptors (also known as odor receptors) compared to the 6 million found in a human nose. This means a dog’s nose is 50 times stronger than ours at picking up scents. What dogs can sense with just their nose is truly remarkable—they’ve even been known to save lives with their nose!

Taking the dog for a walk in the city
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It’s true! Cindy Otto, Director of the University of Pennsylvania’s Working Dog Center, is currently training eight Labrador Retrievers to sniff out COVID-19. If the study is successful, dogs will be able to screen people for coronavirus in airports, hospitals, and other public gathering spots. While these dogs won’t serve as a replacement for tests, they can be used as a non-invasive alternative similar to how dogs are currently used to sniff for explosives in airports, yet we still have to go through security. Check out some other canine heroes who saved their owner’s life.

Senior black woman patting the family dog
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Dogs have an extraordinary ability to track down people by smell, which is why they are used in missing person searches. “Trained search and rescue dogs can follow a scent from footstep to footstep, and can even catch scents in the air,” says Dan Morris from PetNPat. “This is invaluable to us in the task of locating those who are lost because we simply have nowhere near the same capabilities.” Some breeds of dogs are better than others at tracking people, but because of dogs’ olfactory abilities that have adapted over time to ensure their survival, their ability is always better than humans. Learn more fun facts about dogs that you may not have known.

Cancer patient conforted by her dog.
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“Scientists have confirmed that dogs can smell cancer in its early stages, specifically lung and breast cancer,” explains pet expert Peter Laskay. The cancerous tumor produces proteins that dogs can smell in urine. They can sense several types of cancer including lung cancer, bladder cancer, prostate cancer, and breast cancer. Dogs even help out in clinics during the early stages of diagnostics. See what your dog wishes you knew about them.

Side view of pregnant woman relaxing next to dog
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Ovulation and pregnancy

Since dogs are sensitive to the smells in our urine, it would make sense that they can smell our hormones as well. With all the hormonal changes in a woman’s body during pregnancy, dogs are typically able to pick up on those differences. “Of course, hormonal changes are also accompanied by changes in body scents that dogs can smell, even in the early stages of pregnancy,” claims Laskay. Besides pregnancy, learn what other revealing secrets your dog knows about you.

Young woman hugging dog and on living room sofa
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Dogs often understand our emotions better than we can. “When we have changes in our emotions, our hormones change as well (think of stress hormones like cortisol or adrenaline, or happy hormones like oxytocin),” says Jen Jones of Your Dog Advisor. “These hormones are detectable by dogs in our breath and in our sweat.” Since dogs are astoundingly in tune with our smells, and they can detect very minuscule changes to our hormone levels, letting them when we are happy, sad, stressed, or scared. Now, decipher your dog’s emotions with our guide to the noises they make.

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Bed bugs

Bed bugs produce an odor from their scent glands that is only noticeable to humans in very large quantities like when you have an infestation. “Many new forms of pest control involve bed-bug sniffing dogs who, with their incredible noses, can detect this odor in its earliest stages,” explains Jones. “This helps rid homes of bed bugs before an infestation gets out of control. Speaking of gross things your dog likes to smell, don’t miss why your dog likes to sniff another dog’s butt.

Comfy There?
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“New research conducted by scientists at Lund University in Sweden and Lorand University in Hungary have discovered that dogs actually have sensory cells at the ends of their noses that act as sort of infrared sensors,” says Jones. “These cells allow them to detect (or essentially smell) very minute changes in temperature.” This will alert the dog to when people, other dogs, or even predators are nearby. Check out our ranking of the 20 smartest dog breeds.

Boy and dog looking at view of sea, Olympic National Park, Washington State, USA
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Natural disasters

You may have noticed that your dog acts differently when a big storm is approaching. Observations have shown that dogs are able to smell even the slightest changes in the air in addition to changing temperatures, leading them to predict large weather events like a hurricane or a tornado. If your dog loves to snuggle during a storm, you may have one of the 11 most affectionate dog breeds that love to cuddle.

Dog digging
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Scent detection dogs are conditioned and trained to detect a certain chemical. “This scent largely goes undetected to our weaker noses,” says Russell Hartstein of Fun Paw Care, LLC. “However, a dog’s strong sense of smell and large olfactory gland is perfect for detecting these minute levels of chemicals.” A dog’s behavior is explained by their survival instincts, including the reason why they like to bury bones.

Senior Men with His Service Dog and a Best Friend
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Dogs are able to detect a change in blood glucose levels just from a person’s breath which can be especially crucial to those with diabetes. There are even dogs that are specially trained to assist those with severe diabetes to warn them when their glucose levels drop too low. Next, see how these dogs used their sense of smell and their other superpowers to save their owner’s life.


Emma Taubenfeld
Emma Taubenfeld is a former assistant editor for Reader’s Digest who writes about digital lifestyle topics such as memes, social media captions, pickup lines and cute pets. When she’s not working, you can find Emma reading corny young adult novels, creating carefully curated playlists and figuring out how to spice up boxed mac and cheese.