Every dog owner secretly wishes that one day, Fluffy will waken from a nap and do something extraordinary. Maybe her dog, who up until now was only interested in napping and licking itself, will try to communicate some urgent message. “What is it, girl? It’s Timmy? He fell down a well? His leg is broken?” Okay, so maybe Lassie-level heroics are a bit much to ask for. She was a special case, and she set a standard that few other dogs could hope to live up to. While other dogs were chasing their tails in a circle, Lassie was fixing the plumbing and doing her owner’s taxes. I bet that if she had had opposable thumbs, Lassie could have cured cancer.
Manual dexterity aside, even if dogs can’t cure diseases, they might be able to help diagnose them. We already know that dogs are especially intuitive to their owner’s moods and emotions, but there is also mounting evidence that dogs somehow have the uncanny ability to tell when people are sick, helping to identify people with cancer, diabetes, epilepsy, and other diseases.
Scents-itive Sniffers
A pair of English dermatologists were the first to suggest that perhaps dogs could smell cancer. They were inspired by a female patient whose dog would constantly sniff at a mole on her leg, and once even tried to bite the mole off. Upon removing the mole, the doctors discovered that it was actually a malignant melanoma.
Scientists don’t have it fully figured out yet, but the secret weapon might be dogs’ superior sense of smell. Their noses are up to 100,000 times more sensitive than a human’s is and they have the added ability to smell multiple things at once, including complex chemical combinations. Compared with humans, dogs also have a greater portion of their brain devoted to smell, and more nerve connections between the brain and the nose.
It’s not just skin cancer that dogs can detect. Experiments have shown that dogs can diagnose bladder cancer simply by sniffing a patient’s urine and a study published in 2006 by the Pine Street Foundation, a California cancer research organization, found that dogs could identify patients with both early and late-stage lung and breast cancer simply by sniffing their breath. Dogs also helped doctors discover that ovarian cancer has a certain scent that distinguishes it from other gynecological cancers. Even more remarkable is that dogs are up to 97 percent accurate with their diagnoses.
Many diseases leave biomarkers, chemicals, and proteins that are secreted through a patient’s urine or breath. Cancer cells, for example, produce metabolic waste products that differ from those of normal, healthy cells. Patients with a variety of types of cancer have been shown to exhale biomarker chemicals on their breath, including formaldehyde and harmful benzene gas. Any disease has the potential to change the body’s biochemistry, thereby altering the chemical makeup of its waste products. Since dogs can detect chemicals in concentrations as dilute as a few parts per trillion, scientists assume that these chemical markers are what the dogs are reacting to.
Besides cancer, dogs have predicted blood-sugar drops in diabetics as well as seizures in epilepsy patients. Dogs have also predicted heart attacks. Again, the prevailing theory is that dogs are sensing chemical changes in our bodies that we can’t detect on our own. Many organizations across the country are devoted to training these alert dogs, so they can work as service animals for people with otherwise debilitating diseases. With the assistance of a dog, diabetics can prevent low blood sugar by eating carbohydrates or taking an extra dose of insulin. And once a dog alerts an epileptic prone to seizures that one is coming, that person can get herself to a safe place where she won’t be injured. The dogs also tend to stay with their owners while they’re incapacitated, comforting and protecting them.
Old Tricks, New Tricks
Making a diagnosis based on scent isn’t just for the dogs. Doctors have been using their own sense of smell for hundreds of years, because certain diseases are known to be accompanied by strange or specific odors. Diabetes, in particular, was once diagnosed solely by the sweet or fruity smell or taste of a patient’s urine. People with liver disease tend to have foul, fishy breath and doctors have always known that a strong rotting scent on a wound indicates infection or gangrene. Unfortunately, the biomarkers that indicate diseases like cancer are not strong enough for humans to detect. A dog, with its more sophisticated nasal palate, can help make diagnoses easier, enabling doctors to start treatment earlier and save patients’ lives.
Of course, we shouldn’t envision a future where every doctor travels with his diagnosis dog and every sick person has a service animal. While they are useful right now, ultimately scientists want to use what they learn from canines to start researching the chemical compounds to which the dogs are reacting—how does urine from a breast cancer patient differ from a lung cancer patient, for example? Ovarian cancer has a specific scent, but what is it that makes it different from the scent of an impending heart attack? The goal is to isolate and identify the markers, and then develop “electronic noses” that can do the sniffing. We already have the equipment to electronically “sniff” for explosives at an airport … why can’t we electronically sniff for cancer? Disease-sniffing technology could be used in doctors’ offices or carried by sick people, and could help make earlier and more accurate diagnoses, thereby saving countless lives.
Scientists have shown that some dogs show a greater natural aptitude for disease diagnosis, but there’s no one breed that fares better than another, despite marked differences in intelligence between breeds. Their uncanny abilities stem from their stupendous noses and a special relationship with their owners. Every dog has the ability to become a cancer-sniffing hero. Even Lassie didn’t do that.