Can Dogs Detect Disease?

The canine nose is the stuff of legends – able to detect individual scent molecules among thousands, molecules so small that they elude hi-tech sensory equipment. Their noses are used to rescue people, discover drugs, uncover agricultural contraband, sniff out bombs and detect landmines.

But can they detect disease? There has been some evidence that dogs may be able to give early warning to signs of cancer and the onset of epileptic seizures. However, don't rush out and enroll Fido into doggie medical school just yet. In spite of a lot of hype, the evidence is far from conclusive, as the following accounts will show. Though researchers have made some progress, the jury is still out on whether dogs will assume a new role in the field of medicine.

Sniffing Out Cancer

In 1989, a woman went to see her doctor about a mole in her left leg. The mole had been there for quite a few months, but she paid it little interest. Her dog, on the other hand, soon became obsessed with it.

At first, the dog – a cross between a border collie and a Doberman – constantly sniffed or licked at the mole, even through clothing. He eventually tried to bite it off, according to the Lancet, a highly respected British medical journal. The 44-year-old woman decided it was time to get this thing checked out. The mole turned out to be malignant melanoma, a life-threatening form of skin cancer, and it was quickly removed. Her dog, by bringing it to her attention, had saved the woman's life.

Intrigued with persistent reports of such phenomena, Florida dermatologist Armand Cognetta decided to investigate possible medical uses. In 1996, Cognetta borrowed a 7-year-old schnauzer named George, a recently retired bomb-sniffing canine, and asked for help from a veteran dog trainer. The goal was to see if George (who had an uncanny sense of smell, even for a dog) could consistently sniff out melanoma, in both tissue samples and in people.

Normally, a handheld microscope is used to diagnose potential skin cancer, followed by a biopsy. The microscope is about 80 percent effective in early diagnosis, which is why further tests are usually conducted to confirm the diagnosis.

After many hours of training, the gray schnauzer scored nearly 100 percent on identifying melanoma tissue samples. Cognetta then allowed George to "examine" actual patients. He discovered melanoma in four (possibly five, depending on how you look at the results) of seven patients. Cognetta wrote that the results were interesting but far from conclusive. A much larger, more controlled study is necessary to determine if dogs can be trained to reliably detect cancer.

However, if they do have the ability to detect disease, don't expect dogs in medical practices any time soon. The cost to train a dog would be astronomical – $35,000 per dog, with 1,200 hours of training. That costs way more than even an MRI exam. A biopsy would be necessary in any case, because doctors would never base an opinion on a single diagnosis.

The real promise is to discover how dogs are able to do it, and then build a machine to mimic the skill. Studies are underway in seven institutions across the globe to find out why some dogs have this amazing ability.

Detecting Epilepsy

Dogs also have been reported to be able to detect the onset of epileptic seizures, sometimes 20 minutes prior to an attack. The benefit of this is obvious: a person can be forewarned to find a safe place or get help before being incapacitated.

Unfortunately, in spite of the many anecdotal reports of "seizure alert dogs," there is no scientific evidence or documented proof that dogs can be reliably trained to detect the onset of a seizure. The seizure itself is a symptom, not a specific disease. Seizures can occur for a variety of reasons, one of which is epilepsy. Regardless of the cause, the electrical activity in the brain is temporarily disrupted during a seizure. Seizures can be hardly noticeable, or they can be incapacitating.

The Epilepsy Institute has been unsuccessful in its attempts to study whether dogs can reliably predict seizures. The institute used EEG machines and video cameras to monitor epileptics with their dogs. Limited funding did not permit 24-hour monitoring, and during the monitoring no seizures took place.

But finding evidence of this ability would only be a first step. Training a dog to recognize and respond appropriately is the greater challenge. If dogs have this ability, there is no way to know if a dog can be trained with this skill.

"There is no guarantee that a dog, if he can detect a seizure, will do so 10 out of 10 times," explained Beth Rivard, executive director of a nationally recognized service dog program. Rivard heads up the Prison Pet Partnership Program, at Washington Corrections Center for Women, in Washington.

Beginning in 1981, the program has been teaching inmates to care for and train service dogs, which are then placed with recipients suffering from a number of disorders, including epilepsy. When a seizure begins, dogs are trained to stay with the person, and to get a phone or medication if directed to do so. They also know to get help, and may even know to try to roll a person onto his side to prevent choking.

But Rivard said there's no way to train a dog to detect when a seizure is imminent. "It would be a great thing if they can do it, but how do you prove it every time," she said. If a dog senses a chemical change prior to a seizure – which they may – the odor would have to be replicated to train the dog to react the right way, every time. That may be difficult because seizures are electrical disturbances within the brain.

The Epilepsy Institute recommends against getting a dog for the purpose of predicting seizures, and does not recommend any trainers for this purpose. After conducting interviews, the institute concluded that despite the publicity, few people have actually reported that their pets have this ability. Half of those who said their pets did show some ability were more likely to identify behavior during or after a seizure – and not before.

However, the institute noted that enough reports sound authentic enough to warrant more scientific research. To read about one such story, please read Dogs that Can Foretell Seizures.

The institute is pursuing funding to conduct more extensive research, and has developed a pet profile questionnaire to collect data on the subject. After filling out the form, individuals will be interviewed by phone to the likelihood that their pet can detect seizures prior to human awareness.

To learn more about the Epilepsy Institute's Seizure Alert Dog study, call 212-677-8550 or visit their Web site at