Dogs smell a lot of stuff we can't, including bed bugs and chemicals in electronic devices

Efforts to create disease-sniffing capabilities for phones still can't match dogs

In this video, a scientist explains why dogs remain leaders in olfactory capabilities, outpacing technology. Scientists have attempted to create artificial "e-noses" for phones to detect early signs of disease, but so far they have not been successful.

Canine inspectors can help detect potential carriers of invasive insects

At ports of entry in the US, Customs and Border Protection agents use dogs to sniff for forbidden foods and other items that are known to harbor invasive pests. Agents also physically inspect items such as flowers to prevent entry by species that may harm US agriculture.

A dog's nose can be up to 100,000 times more sensitive than a human's, and each possesses a secondary organ for smelling, which helps learn about other dogs when they sniff each other's butts.

Dogs' disease-sniffing skills were first identified in 1989

This capability, reported in the medical journal The Lancet, was discovered when a dog reportedly detected cancer in its handler. The dog repeatedly focused on a spot on the owner's leg where a malignant melanoma lesion was later found, helping lead to an early diagnosis.

Two dogs were able to detect prostate cancer in 98% of patients in one study

In this small study published in 2015, two highly trained German Shepherd dogs sniffed hundreds of urine samples and were able to accurately detect prostate cancer—sniffing out certain volatile organic compounds—in almost every single case. One dog was correct 98% of the time and the other correctly identified patients 100% of the time. (Some users may encounter a paywall.)

A super-sniffer smelled her husband's Parkinson's disease years ahead of symptoms.

A dog's central sniffing organ is many times bigger than a human's

The olfactory epithelium, located high up within the human nose, is home to millions of olfactory neurons. A dog's olfactory epithelium is much larger—and has more neurons—than a human's, which helps to explain the animal's superior sniffing ability.

Scientists determine the smells of objects in outer space

Using spectrographic techniques, scientists determine the chemical composition of planetary atmospheres, comets, and other objects in space. Combining these chemicals in labs on Earth has revealed locations in space that smell like nail polish remover, rotten fish, and urine.

Humans can track smells on the ground quite well—our ability to crawl is a limiting factor

As part of a scientific bet, neurobiology researchers dragged a chocolate bar across the grass and sought to see if a human could track it—she could. This led to a more in-depth experiment on human olfactory capabilities and behavior when other senses were blocked.

Squeaky toys mimic prey sounds, appealing to dogs' hunting instincts

Squeaky toys provide instant feedback and gratification, and they can also prevent boredom and improve canine dental health. Some toys contain seemingly silent squeakers that use ultrasonic technology to emit sounds only audible to dogs.

Fear has a specific 'smell'—at least to machines

This excerpt from a Mythbusters episode takes on the smell-of-fear question, comparing the sweat composition of individuals exposed to snakes, rats, and scorpions with that of people exercising. Molecularly, the sweats are different to a gas chromatography machine, but to most noses would be indistinguishable.

Odor blockers use nonpolar oils to trap smelly polar molecules

In the case of feces, gut bacteria produce compounds such as skatole and hydrogen sulfide, which the brain registers as unpleasant. Because oils do not dissolve in water, they can be used to create a layer on the surface that prevents smelly compounds underwater from escaping into the air.

Bedbug problems have been increasing, and some 2023 research suggests the tiny insects may be capable of spreading 'superbug' MRSA.

Scientists still don't know why DEET is such an effective bug repellent

This chemical, used to keep ticks, fleas, mosquitoes, and other nuisance bugs away, is used by an estimated one-third of the US population and has been available to consumers since 1957. Researchers theorize that multiple mechanisms may be at work to deter bugs, including perhaps masking or confusing bugs' olfactory receptors.

Humans may be able to distinguish more than one trillion scents

That's according to one estimate published in 2014. This figure far exceeds earlier estimates of a human smelling ceiling around 10,000 odors. The newer figure is derived from experiments in which volunteers agreed to sniff varying scents. Researchers mixed odor components and had volunteers sniff the brews to detect subtle scent differences. (Some users may experience a paywall.)

A stand-in 'nose' may help people with anosmia to smell certain odors

In a 2025 paper, researchers reported they'd created a proof-of-concept device that bypasses typical olfactory pathways and instead exploits an alternative—the trigeminal nerve in the nose—to detect a few strong scents. The nerve typically helps detect the temperature of inhaled air or the presence of irritants. (Some users may experience a paywall.)

Why your dog’s DNA isn’t destiny

DNA tests tell people about their pet’s breed and attempt to predict things about its behavior and health. But for all that these tests might provide some interesting results, they need to be taken with caution. Here's a look at what we can and can't learn from our pets' DNA.

Humans can't smell the inside of their nose due to olfactory fatigue

Once a person is accustomed to a specific odor, their neurons have trouble continuing to respond to that smell because of that familiarity. That's why humans may not notice when their house smells like trash until they leave the house and then return to it.

Explore the chemistry of undesired body odors

This graphic highlights some of the main compounds in different body odors, including halitosis (bad breath), flatulence, and foot odor.

Our sense of smell affects what foods taste like and how we perceive it

Scent stimulates our olfactory sensor neurons high in the nasal cavity, and the brain attaches labels to those scents. But when we eat, chemicals from the foods travel from our mouths and throat to those neurons. We have roughly 400 odor receptors, and they can be used to decipher more than 10,000 different odors (or more than one trillion by some calculations), including the nuances of different foods.

Sleep research indicates dogs likely dream about their toys, food, and owners.

Cadaver dogs are helping archaeologists uncover decaying history

Archaeologists are increasingly relying on dogs to help find decaying bodies at burial sites, some of them up to thousands of years old. This is helping archaeologists to detect past remains without ever touching a shovel, which means there's less...

Bug-bitten and bedeviled: a delightful dive into the bedbug

Bedbugs can live up to 6 months without food—meaning they can lurk in your bedroom while you try to eradicate them and give you a sense that you've effectively annihilated them. What else do we know about these pesky little pests? This deep, deep...

Read the academic article explaining how ancient smells can be dissected and recreated

This paper explores how biomolecular data on past scents can be teased out and then transformed into olfactory museum experiences, adding another component to our understanding of archaeology.

Paul Broca, a French brain researcher in the 19th century, hypothesized that humans evolved to trade in our "bestial sense" of smell for higher brain capacity.

Environmental DNA monitoring can help detect the presence of invasive species

Genetic material that organisms deposit into water, soil, or air can be identified by analyzing samples from each environment, allowing land managers to more reliably detect and track organisms than visual surveys alone. eDNA has been used to develop early warning surveillance systems for various invasive marine species.

The science of dogs, from wolf origins to color-blindness

This under 10-minute podcast episode dives into the rich, fascinating science behind dogs: From their world-class sense of smell to their domestication from wolves.

Scent is a stronger memory trigger than sight

Smell is imbued with more emotion than visual memories, and research indicates that smell triggers a significantly greater effect on amygdala activation. Scientists believe these powerful responses occur partly because smell signals bypass the thalamus and go directly to the amygdala and hippocampus, brain areas involved in emotion and memory.

Read a study documenting how 'old people' smell increases with age

Analysis of body odors from individuals aged 26 to 75 confirmed that 2-nonenal, an unsaturated aldehyde with an unpleasant, greasy, and grassy odor, was detected only in subjects aged 40 and older.

How bedbugs have evolved immunity against pesticides

Bedbugs, once nearly eradicated in the United States due to the use of pesticides like DDT, have made a resurgence, with New York being declared the most bedbug-infested city. The primary reason for the return is the evolution of resistance in...

Carboxylic acids are one reason teens are smelly

Scientists compared the smells of babies and teenagers and identified some of the compounds that make teens smelly. Carboxylic acids present in teens, they wrote, seemed to give off an "earthy, musty, or cheesy" scent. This 2024 research could help inform future odor-control products.

The Dog Aging Project uses information from over 50,000 dogs to explore longevity

The study gathers health, lifestyle, and genetic data to understand what helps dogs live longer, healthier lives. Findings could also provide human health insights due to our shared surroundings and biology.

Some animals possess sensitive hearing to help pinpoint prey and map the world

Bats and dolphins produce sound to reflect off surfaces and create a mental image of their surroundings. Owls' faces are dish-shaped to help funnel sounds to their ears, including that of mice moving along leaves or snow. Pinnipeds, such as seals and walruses, hear in both air and water.

Why bean leaves are an effective bedbug pesticide

No one wants a bedbug infestation because getting rid of them is infamously difficult. High heat and diatomaceous earth are two of the most effective bedbug pesticides, but there's another, obscure method: bean leaves! Watch this four-minute video...

Humans have taste receptors throughout the body, including in the testes and lungs, but we don't taste what they detect because those areas lack taste buds.

Despite privacy risks, scientists are using DNA in the air to assess ecosystem health

While DNA in soil and water samples has long been used for such analyses, airborne DNA is being incorporated into such efforts to monitor individual species abundance, detect invasive species, measure biodiversity, and determine the success of conservation actions. Future work may include detecting attacks from biological weapons.

Smell retraining can help people with anosmia learn to smell again

Olfactory training, which involves repeatedly smelling a selection of strong odors, teaches your brain to familiarize itself with experiencing smells over a lengthy period, typically multiple months. This can be useful for patients who lose their sense of smell for myriad reasons.

1 in 15 adults over age 40 experience phantom odors

This phenomenon was measured in a 2018 study that examined the prevalence and risk factors for phantom odor perception. Older adults were less likely to experience these phantom odors as they age, just as their overall sense of smell declines. Women are more likely than men to perceive phantom odors.

Sweat doesn't smell, but bacteria multiply in moist environments—and cause an odor

Body odor is associated with sweat, but odor actually arises from the bacteria that multiply in moist environments on your skin. Hormones, medications, food, and body hair can all affect body odor.

'Old people' smell is real—it's a chemical buildup when fatty acids on the skin oxidize

The chemical composition of body odor seems to change with age. Later in life, we harbor higher concentrations of a chemical compound called 2-nonenal that forms when omega-7 fatty acids on the skin oxidize, and the skin's natural antioxidant defenses weaken. Commonly called "nonenal", it's the smell widely associated with aging, and it's often described as a grassy or greasy odor.

On average, people smell worse if they're sick

For a small 2014 research study, a panel was tasked with sniffing the smelly t-shirts of people who had been injected with a compound known to activate the immune system and those of controls without the shot. It found that those who were acting as if unwell (due to the injection) generally smelled worse. Subsequent work found that those who sniffed unpleasant odors had a mild immune response of their own—perhaps to protect them from disease. (Some users may experience a paywall.)

Typhoid smells like freshly baked brown bread

Certain ailments are associated with documented scents, including diabetes, Parkinson's disease, and typhoid. The skin of people with yellow fever, for example, can smell like a "butcher shop."

Testing five common beliefs about bedbugs

Bedbugs are one of the most stigmatized pest infestations due to their resilience and tendency to dwell where humans are most unconscious for long periods of time: beds. A bedbug problem can lead to horror stories and intensive interventions to...

Heightened sense of smell during pregnancy is not yet well understood

Boosted smell powers and strong reactions to them are often reported beginning around the six-week mark of pregnancy. Researchers say hormonal changes likely play a role, but the change remains poorly understood.

The most unique-smelling places on Earth

Have you ever picked a travel destination by smell? This Atlas Obscura piece cultivates a list of the most distinct-smelling spots in the world. Learn about these obscure scents to potentially book a trip to a spring that smells like rotten eggs, or a desert valley filled with frankincense trees.

Scents, when they are truly unique and identifiable to a particular brand, can be trademarked.

The genetic diversity of dogs is greater within Chernobyl than in surrounding areas

A 2023 study identified that packs of dogs located just 16 kilometers (10 miles) apart within the exclusion zone were more genetically different from one another than from stray dogs hundreds of kilometers away. Rather than radiation, this is likely the result of inbreeding within isolated packs.

Biosignatures are the chemical fingerprints astrobiologists search for to find life

The 21st century has introduced advances making telescopes, cameras, and computers powerful enough to detect the presence of molecules associated with biological processes in distant atmospheres, expanding the search for life to include unreachable worlds.

Olfactory training, a widely recommended treatment for people with long-term loss of smell after a viral infection like COVID, can be performed at home using bottles of essential oils—often lemon, rose, clove, and eucalyptus—to help reorganize neural connections in the brain.

Smell is a robust memory cue for individuals with Alzheimer's disease

Odor is more effective than both visual and verbal cues for triggering autobiographical recall in Alzheimer's disease, according to 2021 research.