Most people know about the exceptional work that guide dogs perform for blind and visually impaired people, and how assistance dogs aid people whose mobility is impaired. But there are other types of assistance dogs that improve people’s quality of life in other ways.

I’ve featured many of these dogs in my book Canine Angels, which I wrote with Carole Villeneuve.

For several years, assistance dogs have been trained to help diabetics to better control their condition, such as at Dogs for Diabetics, a nonprofit organization in California. Thanks to a rigorous training and a well-developed olfactory acuity, these dogs can detect low or high blood glucose levels in their owners’ blood. When that happens, the dog takes something called a bringsel (a small leather strap hooked to the collar) into his or her mouth and makes physical contact with the human. This way, diabetics know that they must check their blood-sugar level. If they ignore or do not respond to this request, their dogs become more intense in the method of contact. Some diabetics wearing an insulin pump with an alarm say that their assistance dogs alert them well before the pump’s alarm starts beeping.

There are also dogs for people with epilepsy. The Lions Foundation Dog Guides offers this type of dog. When an individual has a seizure in a public place, the service dog begins to bark in order to attract people’s attention. When a seizure occurs at home, the dog is trained to fetch a cordless phone and bring it to the owner. In other cases, the dog has to press a button on a specially designed device.

One-third of these assistance dogs can anticipate a seizure well before it occurs, yet no scientific study has explained why. Most of these dogs show signs of agitation and repeatedly circle their owners as if they want to protect them. This gives people with epilepsy time to get to a safe place to avoid injuries during a seizure.

More surprisingly, dogs can be trained to detect cancer in humans. The Pine Street Foundation, located in San Anselmo, CA, published a study based on breath samples contained in tubes, the goal of which was to detect breast and lung cancer. The dogs had undergone only a few weeks of training and worked over a four-month period, investigating 12,295 trials. Each trial was documented on video. The study targeted 55 people afflicted with lung cancer, 31 suffering from breast cancer, and 83 in good health. The five professionally trained dogs, with more than 90 percent accuracy, distinguished people who had cancer from those who did not.

There are also psychiatric service dogs, when medication proves ineffective in alleviating the effects of mental health problems. A psychiatric service dog can perform several tasks. For example, for an individual suffering from major depression, the dog can wake him up in the morning, bring his medication, and find lost objects. For someone with a bipolar disorder, the dog can give a warning at the beginning of a manic episode by performing an alerting behavior, much like with epileptics.

Autistic children also benefit from service dogs, with parents noticing improvements in their children’s language skills, motor skills, and behavior. Some parents even describe service dogs as real therapists.

Canine Angels features chapters on various types of dogs, such as assistance dogs for people with post-traumatic stress syndrome or reduced mobility, and guide dogs for deaf people and blind people. It contains more than 20 testimonials, with people relating how their assistance dog has improved their quality of life. The stories differ greatly in terms of individual disorders and people’s circumstances, but they share the joy of living rediscovered, thanks in large part to the constant support and presence of canine angels.