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Medical Detection Dogs and Their Impressive Ability to Help Us

Linda Crampton is a writer and experienced science teacher with an honors degree in biology. She enjoys writing about science and nature.

Golden retrievers such as Sam have a great sense of smell, which is very useful in a medical detection dog.

Golden retrievers such as Sam have a great sense of smell, which is very useful in a medical detection dog.

Canine Friends and Helpers

Dogs can be wonderful companions and family members. They don’t perceive the world in exactly the same way as us, however. For example, they can’t see as many colors as us, but their senses of smell and hearing are much better than ours. Since dogs are clever animals that are often eager to cooperate with us, their enhanced senses can be very useful to humans.

One exciting discovery about dog behavior is that the animals can detect certain diseases and medical problems in humans. Sometimes they need to be trained to accomplish these tasks, but in other instances, dogs can identify a problem on their own without any training.

Dogs can detect several types of cancer, an epileptic seizure that is about to occur, and infections by Clostridium difficile. Evidence suggests that they can also detect the SARS-CoV-2 virus that causes the COVID-19 disease after suitable training. They might be able to detect low blood sugar (or hypoglycemia) as well, though this is a somewhat controversial idea.

Dogs are believed to detect diseases with their amazing sense of smell. This sense is at least 10,000 times stronger than ours and may even be up to 100,000 times stronger. A dog's nose and brain have special adaptations for sensing and analyzing odors, which we lack.

Researchers have been performing scientific studies with medical detection dogs for at least fifteen years. In this article, I describe research projects from various points in this time period. They aren’t the only ones that exist, but they should give the reader an idea of the fascinating and useful abilities of the dogs.

How Do Dogs Detect Cancer?

Cells produce and release volatile organic compounds, or VOCs. Cancer cells produce a different set of VOCs from healthy cells. Some of the VOCs are different from those made by normal cells, while others are the same but are present in a different proportion.

Volatile organic compounds escape from cells and leave the body in exhaled air, saliva, sweat, blood, urine, or feces. Dogs can smell and recognize the distinct VOC or combination of VOCs made by cancer cells and can distinguish them from the ones made by normal cells.

Dogs detect the presence of the abnormal VOCs in sample containers very quickly. They are trained to show that they've found the chemicals by performing specific behaviors, such as tapping the sample container with their paw or nose or sitting in front of it.

Cancer Types Detected By Dogs

Lung Cancer

Detecting early-stage lung cancer is difficult. There are generally no obvious symptoms, and the normal detection methods aren't very reliable. It's very important to identify any cancer in its earliest stages to give the best chance for recovery.

Researchers in a 2011 experiment tested the ability of trained dogs to detect cancer VOCs in exhaled air. The dogs detected 71 cancer samples out of a total of 100. The dogs also detected that 372 samples out of a possible 400 did not contain cancer VOCs.

Interestingly, the dogs were not confused by the presence of cigarette smoke particles in the samples or by chemicals released by people suffering from COPD (chronic obstructive pulmonary disease). There does seem to be a specific chemical (or chemicals) released by lung cancer cells.

A 2019 experiment with three trained beagles showed that the dogs were 97% accurate in detecting lung cancer by smelling blood serum. They were tested after eight weeks of training. The research team is also training the dogs to detect breast and colorectal cancer.

Lung and Breast Cancer

The Pine Street Foundation is a non-profit organization designed to support cancer patients and research the disease. In 2006, scientists representing the foundation trained five dogs to detect chemicals in the exhaled breath of lung and breast cancer patients.

In an experiment, the researchers found that the dogs detected 99% of the lung cancer samples and gave a false positive result to only 1% of the normal samples. The dogs correctly identified 88% of the breast cancer samples and had no false positives.

In one experiment, a Labrador retriever was able to detect compounds released by colon cancer cells. This is Owen as a puppy.

In one experiment, a Labrador retriever was able to detect compounds released by colon cancer cells. This is Owen as a puppy.

Colon Cancer

In 2011, another researcher studied the ability of one specially trained Labrador retriever to detect colon cancer in breath or stool samples. The dog correctly identified the presence or absence of cancer chemicals in 33 out of 36 breath samples and in 37 out of 38 stool samples. The stool experiment results were as accurate as colonoscopy results. This is a standard test for the presence of colon cancer and involves the use of a camera to photograph the inside of the colon.

Prostate Cancer

Dogs may also be able to detect prostate cancer by smelling urine. In 2015, the results of an experiment with two bomb-sniffing German shepherds were published. The dogs were given urine from 332 men with prostate cancer and 540 people without the disease. One of the dogs was 100% accurate in detecting the presence or absence of cancer. The other was 98.6% accurate.

According to the American Kennel Club, the ten dogs with the best sense of smell (in alphabetical order) are the basset hound, beagle, Belgian malinois, black and tan coonhound, bloodhound, bluetick coonhound, dachshund, German shepherd, golden retriever, and Labrador retriever. Breed may be important when choosing a medical detection dog.

In one trial, two German shepherds were very successful at detecting prostate cancer.

In one trial, two German shepherds were very successful at detecting prostate cancer.

Double-Blind Experiments

It's very important that experiments with cancer-detecting dogs are "double-blind" experiments. At the start of a double-blind experiment, the dogs and the observers are both unaware of which test containers contain cancer compounds and which are cancer-free. This is very important, since observers may give unconscious signals with their body if they see that a dog is approaching the correct container. Dogs can pick up these signals and may indicate that a container contains cancer compounds simply because they notice that the observer is reacting in some way, even if the reaction is very slight.

When assessing any experimental results, it's important to consider factors that may have affected the outcome, such as sample size and the use or lack of a double-blind procedure. It's also important to note whether another organization is able to replicate the experiment and its results.

Training Medical Detection Dogs

Experimental Results

The results of the experiments with cancer detection dogs range from good to excellent. Possible reasons for this variability could be factors such as the differing abilities of the individual dogs or dog breeds used in the experiments, differences in their prior training or willingness to participate in the experiment, or differences in the experimental design. The type and stage of cancer may also play a role. Dogs may be able to detect some types of cancer better than others, or they may be able to detect cancer at one stage of development better than at another stage. More experiments need to be done and they need to involve a larger number of dogs.

Research with dogs is very important, not only because dogs can indicate the presence of cancer very quickly but also because their behavior demonstrates that cancer cells release specific chemicals. The ultimate goal is not to have groups of dogs working in medical labs. Instead, researchers hope to identify the molecules that the dogs are detecting and then create instruments that can correctly identify the presence of these molecules.

Seizure Alert Dogs

Some dogs can predict that a person with epilepsy is going to have a seizure soon, even when the person doesn't realize this. The warning time ranges from under a minute to forty-five minutes—or even longer—before the seizure starts. The advantage of the prediction is that the person can move to a safe area so that they aren't injured during the seizure.

Dogs are being taught to take care of people during and after a seizure. The ability to predict a seizure is a special behavior shown by certain dogs and can't be trained, although it may be encouraged.

Some scientists think that seizure alert dogs are actually detecting the very early stages of a seizure that has already started rather than predicting the seizure. The changes in the person's brain may be creating chemicals which the dogs can smell. The dogs may also be detecting subtle changes in the person's behavior. Whatever the true explanation, dogs can be very helpful for epileptics.

The dogs indicate their discovery to their owner in a number of different ways. Some paw their owners or bark. Others circle their owners, lick them, nudge them, push them into a sitting position, or stare at them.

In 2019, a report published in the Nature journal showed that distinct chemicals are released during a seizure and that the odors of these chemicals could be detected by the dogs involved in the research. The dogs sniffed breath and skin secretions from people experiencing a seizure and from other people and were able to distinguish the seizure chemicals.

A Beagle That Can Detect the Clostridium Difficile Superbug

Clostridium difficile, or C. diff, is a very troublesome bacterium that produces infections in hospitals, care homes, and communities. It causes inflammation in the intestine and diarrhea, which are sometimes severe.

In late 2012, an article published in the British Medical Journal described the efforts of a two-year-old beagle named Cliff. Cliff was trained to detect C. diff in stool and in the air around hospital patients. After Cliff had received two months of training, he was given 50 stool samples contaminated with C. diff and 50 samples without C. diff. Cliff correctly identified all 50 samples with the bacteria and 47 of the ones without bacteria.

Cliff was then taken to two hospital wards to smell the air around patients. He identified 25 out of 30 cases of infection and 265 out of 270 cases without the infection—and he took only ten minutes to inspect one ward. This is a much faster way to detect Clostridium difficile than using a conventional medical test. The faster the diagnosis, the sooner the treatment can begin.

Cliff is not the only dog capable of detecting C. diff. A health agency near my home uses two English Springer Spaniels to detect the bacteria and says that the team has 97% accuracy.


Dogs can be infected by Clostridium difficile. I have read that the infection is more common in dogs that are immunocompromised. Anyone who hopes to use a dog to detect the bacterium should seek a veterinarian’s opinion with respect to safety for their animal, even if the dog is healthy.

Beagles have an excellent sense of smell, which can be very helpful for humans.

Beagles have an excellent sense of smell, which can be very helpful for humans.

Canines seem to detect coronavirus infections with remarkable accuracy, but researchers say large-scale studies are needed before the approach is scaled up.

— Holly Else, via

Canine Detection of the SARS-CoV-2 Virus

In various experiments, researchers have discovered that the ability of dogs to detect the SARS-CoV-2 coronavirus that causes COVID-19 ranges from good to excellent. The dogs are given fluid from a human to smell, such as sweat or saliva. Researchers don’t know exactly what chemicals the dogs are smelling. Some researchers suspect that the dogs are detecting VOCs released by the body when it’s infected by the coronavirus instead of the virus itself.

Based on the results that I’ve seen, the number of dogs in each project has been quite small. Research with a larger number and variety of dogs is needed. Given the seriousness of the coronavirus situation, however, it could be understandable why dogs are already being used to detect the virus at some airports.

Rapid identification of a patient infected by the virus that causes COVID-19 could be very important in places such as airports. Infected patients could be isolated and then tested again by a conventional mechanism that requires more time. This routine of quick isolation could greatly reduce the spread of the disease. The identification of infected people by dogs would be especially useful in the case of patients who don’t have symptoms and don’t realize that they are carrying the virus in their body and shedding it.

We don't know exactly what they (the dogs) are responding to. It's likely that they are not responding to the virus itself but may instead be detecting subtle odors that occur in people infected with the virus.

— Dr. David Dorman, NC State’s College of Veterinary Medicine

Pets and the Coronavirus

There is one concern for pet lovers with respect to dogs searching for the presence of the coronavirus. Dogs can be infected by SARS-CoV-2. The College of Veterinary Medicine at the University of Illinois reference mentioned below says that a small number of dogs are known to have become infected by the virus and that infected cats are more likely to exhibit symptoms than infected dogs.

Based on what I’ve read, it seems that some of the training programs for dogs use body fluids from infected people instead of the virus itself. There may or may not be active virus in the fluids. I think that anyone involved or planning to become involved in training a dog to detect SARS-CoV-2 should read the University of Illinois’s article carefully and consult their own veterinarian.

Labrador retrievers enjoy carrying objects, which can be useful for people with medical problems.This is Owen as an adult.

Labrador retrievers enjoy carrying objects, which can be useful for people with medical problems.This is Owen as an adult.

Diabetes and Hypoglycemia

What Is Type 1 Diabetes?

Dogs might be helpful for people with a blood sugar (or blood glucose) problem. Glucose is an important substance because it's used by cells as an energy source. Insulin, a hormone made by the pancreas, triggers glucose to leave the blood and enter cells. In a person with type 1 diabetes, the pancreas doesn't make insulin or makes only a very small amount. The person must obtain the hormone through injections or an insulin pump in order for their cells to absorb the necessary glucose.

What Is Hypoglycemia?

Blood sugar can fall to a dangerously low level if a diabetic person receives too much insulin relative to the amount of glucose in their blood. This condition is called hypoglycemia, or low blood sugar.

Hypoglycemia can also develop if the person exercises too much, which uses up blood glucose, or if the person doesn't eat enough food, since the digested food supplies glucose to the blood.

Nighttime can be especially risky for some people with type 1 diabetes because their blood sugar level may fall during sleep. Diabetics need to monitor their blood glucose level frequently and make adjustments to their insulin and glucose intake if necessary.

Common Symptoms of Hypoglycemia

Common symptoms of hypoglycemia include sweating, shaking, weakness, anxiety, dizziness, headache, a rapid heartbeat, and confusion. Severe hypoglycemia can lead to seizures, coma, and death.

An affected person may not realize that their blood sugar is low because the warning signs may be too weak or because of the confusion that develops. This is why a diabetic alert dog as a companion may be a life-saver as well as a friend, assuming that they can detect blood sugar problems. This is not yet certain, at least for dogs in general, as described below. The evidence is mixed.

Diabetic Alert Dogs: Positive Reports

Effective diabetic alert dogs are thought to sense a change in body or breath odor when a person with Type 1 diabetes is entering a hypoglycemic state, although it isn't known what chemical or chemicals the dogs are perceiving. Some dogs can reportedly detect high blood sugar as well as low blood sugar.

The dogs are trained to warn their owner in some way when they detect the signs of low blood sugar. They may jump up on their owner, lick them extensively, nudge them, or sit and stare at them, for example. They may also be trained to bring insulin kits or food to the person or to contact other people. Some parents say that the diabetic alert dog in the family will wake them up during the night if their child is experiencing a dangerous drop in blood sugar.

Some diabetics who own diabetic alert dogs say that their pet’s alerts are accurate and agree with the data recorded by their blood glucose monitor. They also say that their dog has given them a wonderful feeling of freedom and peace of mind and is a very close friend.

The Mayo Clinic agrees that the dogs can be helpful for people with blood sugar problems. It lists some precautions for patients, however, including the following ones.

  • Patients must monitor and attempt to control their own blood sugar, even when they have a diabetic alert dog.
  • Dogs may need to be retrained periodically.
  • A dog’s signal indicating a blood sugar problem must be very clear. Licking may be interpreted as a sign of affection, for example, and not as a sign of a problem.

Hope and Hype

Despite the Mayo Clinic’s opinion and the happy reports by some diabetes patients or their relatives, doubts about the effectiveness of diabetic alert dogs exist. Perhaps only certain dogs or breeds can identify blood sugar problems, or perhaps only dogs trained by specific people or organizations can do so, which may be creating confusion. Some people have bought a diabetic alert dog and found that he or she can’t identify their blood glucose difficulties. The animals are very expensive and cost many thousands of dollars. The quote below seems to sum up the situation for me, at least as it exists in the United States.

In 2016, scientists from the University of Cambridge reported that the level of exhaled ispoprene is greatly increased in people with type 1 diabetics who are experiencing hypoglycemia. It's known that dogs can detect isoprene. Despite the headlines, however, the researchers didn't prove that dogs identify hypoglycemia via detecting the isoprene level in exhaled air.

The diabetic alert dog industry is unstandardized and largely unregulated. And the science on a dog's ability to reliably sniff out blood sugar changes is, at best, inconclusive.

— Robert Benincasa, NPR

Using Medical Detection and Alert Dogs

It's unlikely that dogs will be regularly used to detect samples for the presence of cancer or bacteria. Some people have pointed out that like other intelligent animals, dogs can get bored with doing the same thing over and over again.

In addition, they like to be rewarded for success, which is often motivating for them. If they experience long periods of inspecting samples with no positive results and no chance for a reward, they may lose interest in the project. This is why it's important to understand how dogs are detecting disease. This may enable us to create artificial devices that detect the same chemicals as the dogs.

Dogs that can detect medical conditions that may periodically cause emergencies could be very useful. In addition, their companionship may be comforting for the affected person. It's important that anyone who wants to buy a medical detection or service dog goes to a reputable organization that trains and treats their animals well. The potential buyer should also do detailed research using multiple sources of information before purchasing an animal.

Potential Benefits of More Research

Hopefully, more researchers will explore the ability of dogs to detect health problems. If the research shows that the animals can detect disease, additional funding may be provided to the training organizations. This might eventually lead to better detection of some medical problems. In addition, the price of medical alert dogs may decrease, enabling more people to buy them.

Dogs can be wonderful and very loving pets. It's great that some of them can help us with medical problems as well. As more research is done, we may well discover more about the amazing abilities of dogs.


  • Dogs and human cancer detection from Psychology Today
  • Sniffer dogs can be used to detect lung cancer from the ScienceDaily news service
  • Three beagles detect lung cancer from the Medical Xpress news service
  • Lung and breast cancer detection from the Pine Street Foundation
  • Dogs can accurately sniff out early stage bowel cancer from ScienceDaily
  • Prostate cancer detection by dogs from the National Library of Medicine (Abstract)
  • Dogs can identify the scent of seizures from Scientific American (with reference to a Nature report)
  • Identifying a superbug from EurekAlert
  • Using dogs to detect Clostridium difficile (and COVID-19) from the Vancouver Coastal health Authority, or VCH
  • Dogs and the smell of COVID from
  • COVID-sniffing dogs from the news service
  • Coronavirus and a pet information from the College of Veterinary Medicine at the University of Illinois
  • Type 1 diabetes information from the Mayo Clinic
  • The detection of low blood sugar by dogs from the University of Cambridge
  • Information about diabetic service dogs from the Mayo Clinic
  • The hope and hype of diabetic alert dogs from NPR (National Public Radio)

This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

© 2012 Linda Crampton


Linda Crampton (author) from British Columbia, Canada on January 01, 2013:

Hi, Peg. I agree - dogs are amazing animals! Thank you very much for the comment.

Peg Cole from North Dallas, Texas on January 01, 2013:

Fascinating material on an incredible subject. I loved the video of the dogs being trained to sniff out cancer. Amazing animals. Loved the pics too!

Linda Crampton (author) from British Columbia, Canada on December 19, 2012:

Hi, Deb. It is amazing information about dogs! As you say, they can do so many other things to help us, too. Thanks for commenting.

Deb Hirt from Stillwater, OK on December 19, 2012:

This is amazing material. Dogs can do so much, including being helping dogs to those with arthritis and other physical limitations. They tracks during wars, and for police, too.

Linda Crampton (author) from British Columbia, Canada on December 18, 2012:

Hi, Dianna. Yes, it is wonderful that dogs can help detect medical problems! It's great that they have the ability and the willingness. Thanks for the comment.

Dianna Mendez on December 18, 2012:

Wow, this is so fascinating! I love the fact that dogs can be used to help detect cancer, aid in detecting diabetes low-sugar and seizures. How wonderful!

Linda Crampton (author) from British Columbia, Canada on December 18, 2012:

Thank you for the visit, Maren Morgan. It is nice to hear good news when there is so much bad news being reported!

Maren Elizabeth Morgan from Pennsylvania on December 18, 2012:

Thanks for an uplifting, warm-my-heart story. I needed it to balance the bad news pouring out of the media. :)

Linda Crampton (author) from British Columbia, Canada on December 17, 2012:

Hi, b. Malin. Thank you so much for the lovely comment and all the votes!! Yes, I am definitely a dog lover! All the dog photos in this hub - except for the photo of the beagle - show dogs that are or have been a member of my family. I hope you have a very enjoyable Christmas!

b. Malin on December 17, 2012:

What a Wonderful Hub Alicia. Dogs are Wonderful PEOPLE...I'm Serious! They are so attuned to us, and can sense so much. They give so much and expect just a pat, on the head in return. A lot of the information in your Hub is not new to me. But your presentation kept it so Interesting and enlightening, as well as Entertaining.

I'm a Dog lover and I bet you are too. Voted Up, Interesting, Useful, Awesome!

A Very Happy, Healthy Merry Christmas to YOU!

Linda Crampton (author) from British Columbia, Canada on December 17, 2012:

Thank you so much for the comment and the votes, Tom. I agree - dogs are amazing and fascinating! I hope that you have a very happy Christmas as well.

Linda Crampton (author) from British Columbia, Canada on December 17, 2012:

Thank you for the lovely comment, Eddy! Dogs are wonderful animals. It's fascinating to learn about their abilities, and they can be loving and loyal companions.

Thomas Silvia from Massachusetts on December 17, 2012:

Hi my friend enjoyed reading this hub and you did a great job researching this has well. Dogs have a very great sense of smell and it will rival our own sense of smell very easy, dogs also never forget a smell as well. They are very amazing and fascinating creatures. Thanks for sharing this very interesting information it was a awesome read.

Vote up and more !!!

Wishing you a very Merry Christmas !

Linda Crampton (author) from British Columbia, Canada on December 17, 2012:

Thank you very much for the comment and the votes, Bob, and thanks for sharing the interesting information, too! Dogs can be very perceptive, especially with the important people in their lives. It's amazing to think that the dog in your story may have been noticing something as slight as a finger twitch. His behavior must have been very useful to his owner!

Linda Crampton (author) from British Columbia, Canada on December 17, 2012:

Thank you very much for the comment, Martie, and for sharing the hub with your friends! I appreciate your visit.

Eiddwen from Wales on December 17, 2012:

Such a gem on man's best friend ; in more than one way!!Thank you for this wonderful share.


Bob Bamberg on December 17, 2012:

Great hub, Alicia! I was aware of some of the information you provide, but not in such detail. Your hard work made for a most interesting article.

I remember a documentary 6 or 8 years ago about a dog in the UK that warned his owner of her impending seizures. After all was said and done, they think it came down to the fact that the woman's index finger would twitch slightly about 15 minutes before she seized.

That would go along with the reference in your hub to dogs detecting the very onset of the seizure and not predicting it.

Great work. Voted up, useful and interesting.

Martie Coetser from South Africa on December 17, 2012:

How very interesting! I am totally speechless! But buying a trained dog for personal use would be a bit selfish. An entire community should benefit from his talent. I am sharing this with all my friends in South Africa. Thank you, Alicia, for another most interesting hub coming from your pen. You are a walking encyclopedia!

Linda Crampton (author) from British Columbia, Canada on December 16, 2012:

Thank you for the comment, Debbie! Yes, this is exciting information. It's wonderful that dogs can be great companions and can help us detect certain diseases, too. Service and assistance dogs can improve people's lives dramatically, and medical detection dogs are starting to do the same.

Debbie Pinkston from Pereira, Colombia and NW Arkansas on December 16, 2012:

Alicia, this is amazing and exciting news to me! What a great help these dogs will be to thousands of people! I hope that many more dogs will be trained for this purpose. We already know of the great service of seeing eye dogs, and now we have found another great service that dogs can offer their owners!

Thank you for letting us in on this valuable information!

Linda Crampton (author) from British Columbia, Canada on December 16, 2012:

Hi, Mary. I've heard about this cat, too. His name is Oscar (if we're thinking about the same cat). If the reports of his behavior are accurate, it's amazing that Oscar can sense that people are near death, but it's also wonderful that he decides to lie close to them as they die. Thank you very much for the vote and the share!

Mary Hyatt from Florida on December 16, 2012:

Dogs are such amazing creatures! I read somewhere there was a nursing home and a cat who lived there could sense when a patient was about to die. The cat would go into their room and just sit there with them.

Very interesting article. I voted this UP and shared.

Linda Crampton (author) from British Columbia, Canada on December 16, 2012:

Hi, Kathi. Thanks for the visit. The research with medical detection dogs is very encouraging! I'm hoping that more experiments are done, with more dogs being trained and tested in each experiment. It would also be great to discover if some dog breeds are better at detecting disease than others.

I think the research is wonderful, as long as the dogs are treated well and seem happy, which they have done in all the videos that I've seen. At least some of the organizations that train the dogs point out that their dogs live in people's homes and aren't kept in a kennel at the research facility, which I think is important.

Linda Crampton (author) from British Columbia, Canada on December 16, 2012:

Hi, drbj. Yes, I had the "Clever Hans" effect in my mind when I was writing the section about double blind experiments! Good experimental design is so important in order to draw valid conclusions from an experiment. Thank you for the comment and the vote!

Kathi Mirto from Fennville on December 16, 2012:

I've heard of dogs detecting cancer, but I never knew how. Very interesting and encouraging data. I was wondering how they would apply the research. You're sitting in the doctors office and he says, I'll be right back with the cancer detector dog...hee. But then they explained how they would develop technology to detect the chemical odor dogs detect. Dogs are truly man's best friend!

drbj and sherry from south Florida on December 16, 2012:

Amazing is the right word, Alicia, to describe these dogs' ability to detect specific diseases. As long as the experiments are double blind the results can be conclusive. Otherwise you would have something like the 'Clever Hans' effect (as described in my hub: 'The Amazing Horse Who Could Count').

Voted up for your research and fascinating explanations.

Linda Crampton (author) from British Columbia, Canada on December 16, 2012:

Thanks, Bill. I appreciate your comment. Yes, dogs can be wonderful friends to humans! Their sense of smell is amazing, and it's great that they can help us detect disease and health problems.

Bill De Giulio from Massachusetts on December 16, 2012:

Amazing. I have seen and heard about this and it's amazing. They really are man's best friend. Great job, very interesting.

Linda Crampton (author) from British Columbia, Canada on December 16, 2012:

Hi, Bill. Yes, dogs are certainly amazing creatures! I love having them in my life. Thank you for the comment.

Bill Holland from Olympia, WA on December 16, 2012:

I had heard of this before, but not in the detail that you presented it. Dogs are amazing creatures, aren't they? Great job Alicia, and thank you for the great information.

Linda Crampton (author) from British Columbia, Canada on December 16, 2012:

Thank you for the visit and the comment, SmartAndFun. I agree - dogs are great pets, even when they can't detect disease! It's wonderful that some of them can identify the presence of medical problems, though.

SmartAndFun from Texas on December 16, 2012:

This is such a fascinating subject and a great article. Dogs are wonderful as pets, even when they have no other purpose than to be cute and allow us to pet them. However, dogs really are man's best friend when they are able to help us out in this huge way. Dogs have incredible detective powers amd I'm so glad humans have caught on to this and are putting dogs to work saving lives.