How Do Dogs Act When They Smell Illness: Man’s best friend has been renowned for its unparalleled sense of smell, a remarkable gift that far surpasses that of humans. Dogs’ olfactory abilities have earned them a reputation as invaluable allies in various fields, including search and rescue missions, bomb detection, and even sniffing out illegal substances. However, one of the most fascinating and awe-inspiring aspects of canine olfaction is their uncanny ability to detect illnesses in humans.

How Do Dogs Act When They Smell Illness

For centuries, anecdotal evidence has hinted at dogs’ capacity to perceive illnesses, long before any noticeable symptoms arise. Countless stories exist of faithful canines acting unusually around their ailing human companions, inspiring wonder and curiosity among pet owners and researchers alike. Today, scientific studies are shedding light on this extraordinary phenomenon, unraveling the complexities of dogs’ reactions when they smell illness.

At the core of dogs’ exceptional scent detection lies their impressive olfactory system, equipped with approximately 300 million scent receptors, compared to a mere 5 million in humans. This intricate system allows them to identify and distinguish an astounding array of odors with extraordinary precision. Scientists believe that dogs can detect minute chemical changes in a person’s body odor that occur when they are unwell, including metabolic changes, fluctuations in hormone levels, and even the release of specific volatile organic compounds associated with diseases.

How do dogs act when they sense you are sick?

Signs of a Dog Knowing You are Sick

Your dog may also be a little calmer in your presence, be less demanding of walks and playtime, and they may even pull less or be less excited on their walk if they know you are not feeling your best.

When dogs sense that their human companion is sick, their behavior often undergoes subtle yet noticeable changes. These highly perceptive animals can pick up on the slightest alterations in their owner’s scent and body language. In response to illness, dogs may become more attentive and affectionate, seeking physical closeness and comforting their unwell human with gentle nudges or licking. They might also display a heightened sense of protectiveness, staying close to the individual and keeping a watchful eye on them. 

Some dogs may exhibit signs of anxiety or restlessness, reflecting their concern for their human’s well-being. Additionally, trained medical detection dogs might perform specific actions or alert behaviors to indicate the presence of illness, further highlighting their exceptional capabilities. Whether through instinct or training, dogs seem to intuitively grasp when their beloved humans are sick and respond with empathy and unwavering loyalty.

How does a dog act when they smell cancer?

Your pooch may sit and stare quite intently at you at times or it may tap at your with its paw. Sniffing at you is a common sign, as it is the smell of cancer that the dog primarily picks up on. Another thing some dogs may do is follow their owners around more than usual or lie closer to them than normal.

When a dog detects the scent of cancer, their behavior can vary depending on their training and individual temperament. Trained medical detection dogs are often conditioned to exhibit a specific response, such as sitting, barking, or pawing, upon identifying the distinct cancer-related odor. These dogs are extensively trained to recognize and differentiate the specific scent associated with cancer, displaying remarkable accuracy in clinical studies.

For untrained dogs, their reactions may differ, but they might still exhibit subtle changes in behavior when they encounter the scent of cancer in a person. Some dogs may become more alert, curious, or attentive towards the individual, while others might display signs of unease or anxiety. In some cases, dogs may instinctively attempt to comfort the person they sense is unwell, offering extra affection and support.

It’s important to note that while dogs can be remarkable scent detectors, their reactions alone should not be used as a definitive diagnostic tool. If a dog displays unusual behavior around a person, it’s crucial to seek proper medical evaluation from healthcare professionals to accurately detect and address any potential health concerns.

How do dogs smell diseases?

It turns out that cancer and other diseases or infections have a smell. Chemicals called volatile organic compounds are produced by cancer cells. These chemicals have a scent that can be detected by dogs. Dogs can be trained to detect these compounds in the same way they’re trained to detect drugs or explosives.

Dogs possess an extraordinary sense of smell, making them capable of detecting diseases through their keen olfactory abilities. When a person is unwell, their body undergoes various biochemical changes that can alter their scent, even in subtle ways. Dogs, with approximately 300 million scent receptors, can perceive these minute changes and distinguish the unique odors associated with different diseases.

Researchers believe that dogs can detect diseases by sensing volatile organic compounds (VOCs) released through breath, sweat, or bodily fluids, which can act as disease-specific markers. Through specialized training, dogs can be taught to identify these specific scents and respond in a consistent manner, alerting their handlers or caregivers to the presence of a particular disease.

Can dogs sense cancer?

Dogs have also detected ovarian cancer from blood samples and prostate cancer by sniffing a person’s urine. In 2021, researchers reported that a dog trained to detect signs of breast cancer in urine was able to detect breast cancer with 100% accuracy among urine samples from 200 people.

Dogs have demonstrated an incredible ability to sense cancer through their highly developed sense of smell. Numerous studies and real-life anecdotes have highlighted their capacity to detect cancer in humans with impressive accuracy. The specific biochemical changes that occur in a person’s body when cancer is present lead to the release of certain volatile organic compounds (VOCs). Dogs, with their extraordinary olfactory receptors, can detect these subtle chemical alterations in a person’s scent.

Trained medical detection dogs have been successfully trained to identify the distinct odor associated with various types of cancer, including lung, breast, ovarian, and bladder cancer, among others. Their detection rates in some studies have exceeded 90%, showcasing the potential of these canine scent detectives as a valuable tool in early cancer detection.

While dogs’ cancer-detecting abilities are astounding, they are not a replacement for conventional medical diagnostic methods. Instead, they offer a complementary approach that can aid in identifying cancer at its early stages, potentially leading to more timely and effective treatment interventions. As research continues, the integration of dogs’ extraordinary olfaction into cancer detection strategies holds promising possibilities for improving human healthcare.

How Do Dogs Act When They Smell Illness

How do dogs typically behave when they sense illness in their human companions?

When dogs sense illness in their human companions, their behavior often reflects their heightened sensitivity to subtle changes in the person’s scent and demeanor. Dogs are known for their remarkable ability to detect biochemical alterations and volatile organic compounds associated with various medical conditions, making them perceptive “canine diagnosticians.”

A dog’s reaction to a sick human varies based on individual temperament, breed, and level of training. However, some common behavioral patterns emerge. Dogs may display increased attentiveness and a heightened sense of protectiveness towards the unwell individual. They might seek physical closeness, offering comfort through gentle nudges, licking, or leaning against their human.

Dogs may become more subdued and subdued, mirroring the subdued mood of the sick person. They may spend more time by their side, refusing to leave their presence even for daily activities they usually enjoy.

What are some common observable changes in a dog’s behavior that might indicate they have detected an illness in a person?

When a dog detects an illness in a person, their behavior can undergo notable changes, serving as observable cues for their heightened perception of the individual’s health status. Some common behavioral changes include:

Increased attention and concern: Dogs may become more attentive and focused on the sick person, often displaying a heightened sense of concern and vigilance. They might closely monitor the individual’s movements and show a reluctance to leave their side.

Protective behavior: Dogs may exhibit a protective instinct towards their unwell human companion. They may position themselves between the sick person and strangers or other animals, showing a strong sense of loyalty and guardianship.

Affectionate gestures: Dogs are known for their empathy, and when they sense illness, they may offer comfort through affectionate gestures like gentle nudges, licking, or leaning against the person. These actions can be interpreted as their way of providing emotional support.

Changes in appetite and activity level: Some dogs may experience alterations in their own behavior when they detect illness in their human. They might lose interest in food, exhibit restlessness, or become quieter and more reserved.

Alerting behavior: Trained medical detection dogs, specifically conditioned to identify certain illnesses, may exhibit trained responses upon sensing disease. These can include barking, sitting, or pawing at the affected area, signaling the presence of the targeted medical condition.

Are there specific medical conditions or illnesses that dogs are known to be particularly adept at detecting through their sense of smell?

Dogs have demonstrated exceptional capabilities in detecting specific medical conditions through their keen sense of smell. Their extraordinary olfactory receptors allow them to perceive unique scents associated with various illnesses and health conditions. Some of the medical conditions that dogs are known to be particularly adept at detecting include:

Cancer: Dogs have shown remarkable accuracy in identifying certain types of cancer, such as lung, breast, ovarian, and bladder cancer, among others. They can detect cancer-related volatile organic compounds (VOCs) in a person’s breath, urine, or sweat.

Diabetes: Dogs can sense changes in blood sugar levels through scent, alerting individuals with diabetes when their levels are too high or too low. This early warning can help prevent potentially life-threatening situations.

Epilepsy: Some dogs are trained to predict seizures in individuals with epilepsy. They can detect subtle changes in scent or behavior before a seizure occurs, providing a valuable alert system.

Infections: Dogs have been known to detect infections, such as bacterial or fungal infections, by recognizing specific odors emitted by the pathogens.

Migraines and Headaches: Some dogs can sense impending migraines or headaches and provide warning signals to their owners, allowing them to take necessary precautions or medications.

In the context of medical detection, how do trained dogs differ in their responses to smelling illness compared to untrained or non-specialized dogs?

Trained dogs and untrained/non-specialized dogs exhibit notable differences in their responses when smelling illness in the context of medical detection. These distinctions arise from the intensive training and conditioning that medical detection dogs undergo to identify specific scents associated with various medical conditions.

Trained medical detection dogs have been meticulously taught to recognize and respond to particular odors linked to diseases like cancer, diabetes, epilepsy, and infections. Through positive reinforcement and repetitive training, these dogs develop a reliable and consistent response when they encounter the scent of illness. They might exhibit specific trained behaviors, such as sitting, barking, or pawing, to indicate the presence of a targeted medical condition.

Untrained or non-specialized dogs may also react to the scent of illness but lack the precision and reliability of trained medical detection dogs. Their responses can vary widely based on their individual temperament and experiences. Some untrained dogs may display increased attention or concern when they sense something is amiss in their human companion, while others may not show any observable reaction at all.

How Do Dogs Act When They Smell Illness


The remarkable abilities of dogs to detect illness through their acute sense of smell continue to captivate and inspire both researchers and pet owners alike. Their highly developed olfactory receptors enable them to identify subtle changes in a person’s scent, indicative of various medical conditions. As we delve deeper into understanding this fascinating phenomenon, it becomes evident that dogs play a significant role as invaluable allies in the realm of medical detection.

When dogs sense illness in their human companions, their behavior speaks volumes about their empathetic nature and unwavering loyalty. They often display heightened attention, concern, and protectiveness towards the unwell individual, providing emotional support and comfort during challenging times. Trained medical detection dogs, in particular, offer a specialized and precise response, thanks to their extensive training in recognizing specific scents associated with diseases like cancer, diabetes, epilepsy, and infections.

While dogs’ intuitive abilities have opened new doors in healthcare, it is essential to remember that their responses should not replace professional medical diagnosis. Instead, they should be viewed as complementary to existing diagnostic methods, potentially aiding in early disease detection and improving treatment outcomes.

As research continues, the potential applications of dogs’ olfactory talents in medicine are vast and promising. From revolutionizing cancer screenings to enhancing the management of chronic illnesses, these canine scent detectives hold immense potential to contribute significantly to human healthcare.