Dogs That Changed the World introduced Daisy and Tangle, dogs able to sniff out cancer cells, and Delta, a German Shepherd who can sense changes in the blood sugar levels of her young master. The talents of these special animals are matched by those of tens of thousands of remarkable canines — dogs trained to sense disease and seizures, to assist the physically and emotionally disabled, and to provide comfort, affection, and therapy to their human companions.

Medical Research

Daisy and Tangle were trained to detect the unique odor of bladder cancer cells in urine samples, but researchers have found that dogs can also nose out other forms of cancer. At the Sensory Research Institute at Florida State University in Tallahassee, scientists have trained dogs to detect the odor of skin melanomas and prostate cancer. In 2006, researchers at the Pine Street Foundation in Northern California reported that they had taught dogs to pinpoint patients with lung cancer (with 97 percent accuracy) and breast cancer (with 88 percent accuracy)-simply by sniffing their breath. The researchers are now training dogs to detect ovarian cancer.

Service Dogs

Dogs like Delta are trained to detect subtle changes in a diabetic patient’s body chemistry that occur when the levels of glucose in the blood drop too low or rise too high. Either can lead to seizures, convulsions, diabetic coma, and death. Other dogs have been trained to respond to heart attacks, and to recognize changes in the blood pressure of their owners.

Delta, a German Shepherd, can sense changes in the blood sugar levels of her young diabetic master.

Dogs known as seizure dogs (or seizure response dogs) have been trained or have learned to react when a person with epilepsy is having a seizure. These dogs might bark to notify others of the seizure, lie down next to the person to prevent them from harm, remove dangerous objects from the vicinity so the person is not harmed, or attempt to revive the person after the seizure ends if they lose consciousness. More remarkably, the companion dogs of epileptics may learn to sense an impending seizure in their owner before it happens. In a 1998 survey by researchers at the University of Florida, 10 percent of epileptic patients with companion dogs reported that their dogs seemed to know when they were going to have a seizure. Although experts aren’t sure exactly how dogs do this, it may be that they are detecting subtle changes in body chemistry or in the behavior of their owner. In some cases, these dogs have been trained to perform a particular activity — running in circles, for example-to notify their owner of what they have sensed.

The most widely used and well-known service dogs are those trained to provide assistance to blind or visually impaired people, acting as the eyes of their owner. There are also hearing dogs, trained to assist deaf people and to alert them to sounds such as smoke alarms, doorbells, and crying babies; mobility assist dogs, which pull wheelchairs and provide help to the physically impaired; and walker dogs, which help provide balance when walking to individuals suffering from movement disorders such as Parkinson’s disease and spasms. In addition, dogs have been trained to assist persons with psychiatric conditions such as bipolar disorder, post-traumatic stress disorder, autism, schizophrenia, and anxiety disorder. These dogs learn to recognize changes in their owner’s behavior or environment that indicate paranoia, panic attacks, hallucinations, or potentially harmful repetitive actions, for example, and may remind them to take medication.

Therapy Dogs

Therapy dogs provide comfort and affection and improve the general well-being of people in hospitals, nursing homes, mental institutions, retirement homes, schools, and even prisons. In addition to providing companionship, researchers are now finding that the dogs are legitimately therapeutic. For example, in a 2005 study by the American Heart Association of hospitalized heart failure patients, researchers found that a 12-minute visit with a therapy dog reduced blood pressure and levels of stress hormones, and eased anxiety. Therapy dogs have been shown to improve the focus and memory of patients with Alzheimer’s, encourage speech and simple physical activities among stroke victims and individuals with impaired mobility.

Many organizations now test and provide accreditation to therapy dogs. The dogs must meet rigorous standards of temperament and obedience; they have to be accepting toward friendly strangers, sit and stay on command, be able to walk through a crowd with wheelchairs, and not startle easily.