People know that dogs have great senses of smell. Dogs can smell sickness or disease because they have such a good sense of smell. People only have five to ten million olfactory receptors, while dogs have more than two hundred million. This means that dogs can smell things that we can’t even think of. Dogs can smell 10,000 to 100,000 times better than people. Some smells can be detected at a level of parts per trillion, and they can tell the difference between many small differences in smells.
Some dogs have found health problems that not even doctors were aware of. Dogs can pick up on small changes in a person’s body, like a small shift in hormones or the release of volatile organic compounds (VOCs) from cancer cells. Researchers and dog trainers are just starting to figure out how dogs do this and how we could use them to help with health care. Here are six kinds of health problems that dogs can smell.
Fear and Stress
People have known for a long time that dogs can smell fear. Even if we don’t show it, dogs can smell when we’re scared or stressed, even if we don’t show it. When we’re stressed, our bodies release a lot of hormones, like adrenaline and cortisol. This is what the dogs can smell. When dogs smell fear, they show signs of stress.
People can use this to their advantage, though. Dogs can tell their owners (or other people) to take a few deep breaths. Dogs that can tell their owners when their emotional state changes—a change that people often don’t even realize they’re going through—can help stop panic attacks and other problems that could be caused by PTSD or other problems.
A big study in Sweden that looked at 3.4 million people found that having a dog makes you less likely to get stressed out or get heart disease.
We still don’t know what dogs smell when they come close to us, let alone how to train them to be as accurate as possible when they notice a change in our bodies. Even though we don’t know much about it yet, it’s clear that dogs have an uncanny knack for finding certain health problems, which could save lives.
Cancer
Dogs may be best known for being able to find cancer. Cancers like breast, prostate, bladder, and lung cancer have all been found by dogs.
There are many stories about dogs that are obsessed with a mole or another part of their owner’s body. When the owner goes to the doctor, they find out that the dog was actually smelling cancer. In one study, a man’s dog kept licking a mole that was behind the man’s ear. When the mole was looked at, it was found to be malignant melanoma.
A 2019 study found that dogs can 97% of the time pick out blood samples from people with cancer. Lead researcher Heather Junqueira used clicker training on four beagles to find that the dogs worked hard to get blood samples from lung cancer patients, and with one exception, they were very successful. The work is part of a larger study that looks at how dogs can smell breast and non-small-cell lung cancer samples.
In 2006, five dogs were taught to use breath samples to look for cancer as part of a study. Once they were trained, the dogs could find breast cancer 88% of the time and lung cancer 99% of the time. They did this for all four stages of each disease.
When given urine samples from women with cervical cancer, cervical abnormalities, benign uterine disease, and healthy volunteers, a dog that had been trained to do so could always tell which sample came from a woman with cervical cancer.
Study after study has shown that dogs can find cancer in people, but your doctor may not use a hound during your annual checkup for a while. Researchers still don’t know exactly which chemical compounds for different kinds of cancer the dogs are picking up on in these samples to alert them to the presence of the disease. This is still a problem for better training of dogs that can sniff out cancer and making machines that can find cancer earlier and more accurately.
How does the dog act?
The way the dog acts is different from what you might think is normal. It may keep pawing or sniffing you, and it may be hard to get it to stop. It might try to get rid of wounds by nibbling or licking at them.
Seizures
Scientists don’t know yet if dogs can be taught to recognize specific signs (like a smell) that a seizure is about to start. We can, however, teach dogs what to do and how to help when their owner has a seizure. Some service dogs that are given to people who have seizures can learn to tell when a seizure is coming and can warn their handlers if they pay close attention to the dog’s signs.
In 2019, a small study of five dogs found that the dogs could tell when a person was having an epileptic seizure by their smell and when they were not.
Because the study only looked at a small number of dogs and used odor samples that had already been taken, researchers admit that a lot more testing would need to be done to see if dogs could really predict seizures before they happened and if other dogs would react the same way.
In 2003, 29 people with epilepsy who had dogs said that when they were having a seizure, their dogs did something.
Even though these results may show that some dogs are born with the ability to sense or react to seizures, the researchers know that more research is needed to find out how to train dogs to be as helpful as possible.
How does the dog act?
When a dog senses that its owner is having a seizure, it may act strangely by barking or pawing at them. Since these could be very subtle signs, the dog’s owner would probably need to know the dog well to tell the difference. Some dogs are trained to help their owners during seizures, but they can’t always tell when one is coming on. These will stay with their owners, standing or lying next to them and sometimes licking their faces.
Narcolepsy
Narcolepsy is a condition that makes it hard to decide when to sleep and when to wake up. People who have narcolepsy can fall asleep at any time, even if they are doing something. A person having an attack could get hurt if they fall down or if it happens while they’re driving.
Since 2010, Mary McNeight has taught people with narcolepsy how to train service dogs. She is in charge of how dogs are trained and act at Service Dog Academy. She thinks that the dogs can smell when she is about to have a narcolepsy attack.
In a 2013 study by Luis Dominguez-Ortega, M.D., Ph.D., two trained dogs were able to find 11 out of 12 people with narcolepsy by sniffing their sweat. This shows that dogs can pick up on a scent that is unique to the disorder.
How does the dog act?
If a dog is trained to recognize narcolepsy, it will bark, nudge, or lick its owner to let them know. This makes it clear how important it is to sit or lie down. When an attack starts, the dog can stand over the person’s lap to keep them from falling out of their chair and onto the floor. If the person is in public, the dog can stand over them to protect them, or the person can go get help. Most importantly, they can warn their handlers up to five minutes before an attack starts, giving them time to get to a safe place or position.
Large dogs can help people with narcolepsy keep their balance and move around after an attack, but the dogs don’t have to be big to be helpful. It might help to end the episode by licking the owner’s face or waking them up if they sleep through the alarm clock.
Low Blood Sugar
People with diabetes are training more and more dogs to tell them when their blood sugar level is going up or down. Dogs4Diabetics is one group that trains service dogs and helps people with diabetes who need insulin to find homes for them. These dogs have to go through a lot of training to be able to tell when their owners’ blood sugar levels change and tell them.
In 2016, the American Diabetes Association published a study in the journal Diabetes Care that found dogs can smell isoprene, a natural chemical that rises a lot in people’s breath when they have low blood sugar. Researchers think that dogs are especially sensitive to the chemical and can tell when their owner has a lot of it on their breath.
A 2013 study published in PLOS ONE found that for insulin-dependent people with diabetes, having an alert dog seems to make a big difference in their safety and quality of life. People who had dogs said that they felt more independent and that they fell asleep less often. They also called an ambulance less often.
There are a few ways that people think dogs can tell if someone has hypoglycemia. These changes include chemical changes that the dogs can smell and changes in how the dog acts. No one is sure if dogs can tell their owners when their blood sugar changes in a way that is more likely than not. In 2016, a study with eight dogs looked at how reliable dogs were at recognizing low blood sugar and warning their owners about it. 36% of the time, the animals were able to do this. In 2019, a slightly bigger study with 27 dogs showed that 81 percent of the dogs could tell when their blood sugar levels were too high or too low. Because the success rates in these studies vary so much, more research needs to be done.
How does the dog act?
If a person’s blood sugar drops low enough to cause hypoglycemia, which can cause shaking, loss of consciousness, and even death if not treated, a trained dog can wake up the person or let them know something is wrong. They might jump on the owner, paw at them, or push them. If a dog hasn’t been trained, it may show signs of pain or worry. Retrievers and Labradors are often used to find things because they are smart and learn fast.
Migraines
For people who get migraines, knowing when one is coming on can mean the difference between being able to handle the problem and being in a lot of pain for hours or days. Some dogs can smell when someone is getting a migraine, which is good.
A survey asked people with migraines and dogs if their dogs did anything different before or during a migraine. 11 Out of the 1,029 people who took part in the study, 54% noticed changes in their dog’s behavior right before or at the start of their migraine. The dog was more attentive when it was sitting on or near its owner, and it would paw at the owner on purpose. According to their owners, mixed breeds, toy breeds, terrier breeds, and sporting breeds were most likely to let their owners know when they had a migraine.
It’s important to know that the study was done by people reporting on themselves, not by researchers watching. Even so, the study shows that many dogs seem to be able to notice a change in their human friend’s health and let them know.
How does the dog act?
If your dog knows you’re about to get a migraine, he or she might lick you, circle you, nudge you, stay right by your side, stare at you, pace, or bark. This could remind you to take medicine that would stop the headache from getting worse.
