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Flu season is upon us, and from past experience, you probably had your dog to comfort you if illness strikes. Dogs just seem to know when you’re feeling under the weather. They lie beside you or cuddle you just when you need it most. How do they know something is wrong? Whether it’s flu, or something more serious, do dogs know when you’re sick? And if so, what could they be noticing?

Do Dogs Know When You’re Sick?

Dr. Mary Burch, a certified applied animal behaviorist and the director of the AKC Family Dog program, believes dogs know when something is wrong with a person’s health. She had a personal experience with her own dog Wyn.

“Years ago, I had a life-threatening illness. When I came home from the hospital, I was in bed when my heart began to beat faster and it felt like it was pounding,” she says. “My dog, who was across the room in his bed, ran and jumped on my bed and pushed his head onto my chest over my heart. Within a few minutes, the incident passed and Wyn returned to his bed. I don’t know that he had anything to do with my heart rate returning to normal, but he certainly sensed from a distance that something was wrong.”

German Wirehaired Pointer getting attention.
©rodimovpavel -

What could Wyn have noticed? Although it’s tempting to think dogs have some kind of sixth sense that lets them discover human health problems, there are far more likely explanations for Wyn’s behavior. Perhaps he heard or smelled something out of the ordinary. It could have been the way Dr. Burch was acting or her emotional state. Or it may have been a combination of all three.

Dogs Can Smell Illness

Dogs sense the world differently from humans. For example, they can hear high-pitched sounds people can’t and their sense of smell is unbelievably powerful. Wyn may have heard something different about Dr. Burch’s heartbeat, but it’s just as likely he smelled something wrong. The human body is a complex cocktail of chemicals that gives off odors our dogs can easily detect. In fact, a scientific study showed that dogs can tell identical twins apart even if those twins live in the same house and eat the same food. So, dogs know a person’s individual smell and when illness changes that smell, dogs can notice that, too.

Even humans can observe the scent of sickness with some health problems. For example, diabetic ketoacidosis can cause fruity or acetone-smelling breath. However, with their powerful noses, dogs can detect many odors that humans are simply unaware of. For example, diabetic alert dogs can tell when their owner’s blood glucose levels are off because of changes in volatile organic compounds in their owner’s exhaled breath. And dogs have been shown to detect various types of cancer simply by sniffing samples of a patient’s tissue or even just their breath or urine.

So, if illness changes your body chemistry and your dog knows how you’re supposed to smell, it shouldn’t come as a surprise when they react to your illness. As Dr. Burch explains, “Considering that dogs can detect cancer, diabetes, and seizures, we have every reason to believe that our dogs know when we are sick. Illness results in chemical changes in the body and changes in hormones and these changes can be detected by the dog’s extraordinary sense of smell.”

Dogs Can Understand Body Language and Changes in Routine

But that’s not all dogs might be noticing when they react to their owner’s ill health. According to Dr. Burch, dogs pick up on other cues. “When a normally active owner gets in bed in the middle of the day or takes to the couch and doesn’t move, the dog knows something isn’t quite right,” she says. “Depending on the illness, the owner may be exhibiting symptoms that are easy for the dog to detect. Sneezing, a runny nose (that the owner is blowing frequently), or gastrointestinal issues are other signs for the dog that the owner is not well.”

As anybody who owns a dog with separation anxiety knows, dogs learn every step of daily routines. And they know when something is different. Your dog might become anxious if you don’t let them out when you normally do or spend the day sleeping.

Golden Retriever therapy dog visiting a young girl in the hospital.
Monkey Business Images/Getty Images Plus via Getty Images

Dogs also read human body language extremely well. Even free-ranging dogs can follow human pointing gestures. So, your dog is constantly watching you and interpreting your behavior. When you act out of sorts, it’s unlikely to escape your dog’s notice.

Dogs Can Read Human Emotions

Additionally, dogs can read human emotions. Your dog can hear your mood in your voice and is likely to react positively to happiness and negatively to sadness and fear. Dogs can also match the mood of your voice to the look on your face, knowing that a happy voice matches a happy expression.

Recent research has shown that dogs can use your emotional state to predict your behavior and, more amazingly, adjust their decision-making accordingly. So, your dog isn’t just attending to your body language, but your mood as well. And who feels good when they’re sick? It’s likely dogs can detect the change in your emotional state whenever you feel under the weather.

Why Do Dogs Comfort Sick People?

So, if your dog knows when you’re sick, why do they react the way they do? Are they looking to comfort you or are they seeking comfort from you because something isn’t right and that’s making them anxious? It might depend on the dog. And it might depend on how you respond to your dog’s attention when you’re sick. If your pet earns rewards for cuddles and snuggles, it will reinforce the behavior, making it more likely to occur the next time you’re feeling ill.

Or maybe dogs just like making us feel better. They might sense the changes in a person’s body chemistry that result from their presence and be reinforced by that alone.

“Owners of therapy dogs often say that their dogs seem to know the person in the room who needs them most,” Dr. Burch says. “When a dog gets close to someone who is sick or depressed, the dog could be sensing a decrease in hormones such as oxytocin, dopamine, and serotonin. Studies have shown that petting a dog can reduce a person’s blood pressure, and the dog may sense it can make a person feel better.”

Related article: Do Dogs Have Belly Buttons?
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