Dogs have been man’s best friend for thousands of years. We rely on them for companionship, security, hunting, and more. But can our canine companions also detect when we’re sick or injured? There is some evidence to suggest dogs have the remarkable ability to sniff out human diseases and health conditions.
The Dog’s Incredible Sense of Smell
A dog’s sense of smell is their primary sense. While humans have about 6 million olfactory receptors in their noses, dogs have a staggering 300 million! Their powerful noses can detect odors at concentrations nearly 100 million times lower than humans can.
This allows dogs to pick up on incredibly subtle smells we aren’t even aware of. Dogs can be trained to detect drugs, explosives, cadavers, criminals, and more based on scent alone. Some dogs can even detect COVID-19 by sniffing human sweat!
With such an acute sense of smell, it makes sense dogs may able to smell other changes in our bodies when we are unwell. But what does the science say?
Studies on Dogs Sensing Cancer
There has been a great deal of research into whether dogs can detect cancer in humans. Studies have shown trained dogs can detect lung, breast, ovarian, bladder, prostate and colorectal cancers with high accuracy, often surpassing standard screening tests.
Some key findings on dogs sensing cancer include:
Lung Cancer
– In a 2011 study, dogs were trained to distinguish breath samples between lung cancer patients and healthy controls. The dogs correctly identified lung cancer with 71% sensitivity and 93% specificity.
Breast Cancer
– Dogs trained to detect breast cancer in breath and tissue samples had up to 88% accuracy in one study.
– Another study found dogs could detect breast cancer from blood samples with 97% sensitivity and 94% specificity.
Prostate Cancer
– One study showed dogs could detect prostate cancer from urine samples with 91% accuracy. They could even differentiate between aggressive and non-aggressive cancers.
Ovarian Cancer
– In several studies, dogs have detected ovarian cancer in tissue and blood serum samples with accuracy rates of between 88-97%.
Bladder Cancer
– Dogs trained to detect bladder cancer in urine samples had a detection rate of 41%, compared to 14% for standard urine cytology screening.
Colorectal Cancer
– One study found dogs were able to detect colorectal cancer from stool samples with 97% sensitivity and 99% specificity.
Researchers believe dogs can detect cancer by smelling volatile organic compounds in bodily fluids or breath. Cancer cells produce different metabolic waste products than normal cells, allowing dogs to tell the difference using their incredible sniffers.
Detecting Diabetes
Diabetes is another health condition dogs seem capable of sniffing out. There are studies indicating well-trained dogs can detect low and high blood sugar in diabetics.
In one study published in PLOS One, researchers trained Labrador retrievers to identify the odor of hypoglycemia (low blood sugar). The dogs were able to identify low blood sugar samples taken from children with type 1 diabetes with high rates of accuracy. They also generated very few false alerts.
This could make diabetic alert dogs a reliable way for diabetics to monitor blood sugar fluctuations. The dogs alert owners about drops in blood sugar before they become dangerous. Some key findings on dogs detecting diabetes include:
Hypoglycemia Detection
– In one study, two trained dogs had 98% and 97% accuracy in identifying low blood sugar samples.
– Another study found dogs could alert their diabetic owners to 83% of hypoglycemic episodes in everyday life.
Hyperglycemia Detection
– Specially trained dogs have also been able to detect high blood sugar with about 90% accuracy.
– In real-world tests, diabetes alert dogs detected 19 out of 20 hyperglycemia episodes.
Dogs likely smell ketones, chemicals produced when blood sugar is too high or too low. This allows them to detect dangerous blood sugar changes.
Seizure Detection
Many owners of dogs with epilepsy report their pets can sense an oncoming seizure. Studies have looked at dogs’ abilities to warn epileptic owners of impending seizures.
In a 2019 survey of dog owners whose dogs had epilepsy:
– 72.3% reported their dogs could sense seizures
– 63.9% said their dogs alerted them during the prodromal phase before a seizure
– The mean amount of time between a dog’s warning and seizure onset was 27.6 minutes
This suggests some dogs can detect subtle changes that occur right before a seizure. This likely allows the dogs to warn their owners of seizures minutes or even hours before they occur.
It’s thought dogs may notice subtle behavioral or odor changes during the pre-seizure phase. For example, slight muscle tremors or twitching could tip off dogs that a seizure is imminent.
Sniffing Out Infections
Bacteria produce unique chemicals and metabolic byproducts called volatile organic compounds. Since dogs have such an amazing sense of smell, it makes sense they can sniff out certain bacterial infections.
Studies have shown dogs can detect infections common in hospitals, like:
C. difficile
– Dogs trained to sniff out Clostridium difficile had 100% accuracy in stool samples.
MRSA
– In one study, dogs were able to identify MRSA with 83-94% accuracy in cultures taken from infected patients.
Urinary Tract Infections
– Dogs trained to detect UTIs using urine samples were 98% accurate in some research. This could lead to faster UTI screening.
Detecting COVID-19
Since COVID-19 exploded into a global pandemic, scientists have been studying whether dogs can detect SARS-CoV-2 infections. COVID-19 changes the metabolic processes in the body, so there’s potential for dogs to sniff it out.
Early research results on dogs sensing COVID-19 are extremely promising:
Sniffing Out COVID in Sweat
– In a 2020 study published in PLOS One, detection dogs were able to identify COVID-19 positive samples with 96% accuracy and COVID-19 negative samples with 99% accuracy.
Detecting COVID in Breath & Urine
– In another study, dogs could identify people with COVID-19 by smelling their breath and urine with high rates of accuracy after only a short training period.
Using COVID sniffing dogs at airports and other public places could be a fast, cheap screening method for infection. However, more research is needed to demonstrate dogs’ reliability outside controlled lab conditions.
The Takeaway on Dogs Sensing Illness
The evidence seems clear that dogs can detect some cancers, low blood sugar, seizures, infections and possibly COVID-19 by smell. However, the research is limited and it’s unclear how reliable dogs are at sniffing out illnesses in real-world conditions. More studies are needed to understand the full extent and accuracy of dogs’ diagnostic abilities.
If you notice your dog fixating on you, this may be their instinct kicking in to alert you to a health problem. Pay attention to your canine companion if they seem very focused on smelling you for extended periods. It’s possible Fido knows something about your health you don’t! Discuss any concerns with your doctor.
While dogs may be able to smell some diseases, they should never replace professional medical care. But tapping into dogs’ rich olfactory abilities could lead to earlier disease detection and intervention, saving lives. Their superhero sniffers might make our best friends even better guardians of our health.