Common Sense Health: There's a reason they're man's best friend - The Independent

What a wonderful world if people could be as generous to humankind as dogs. Regardless of our faults, dogs provide unfailing loving care. A new study suggests dogs may be able to use their sniffing powers to know when someone is having a really bad day.

Who knew there is an aroma to being stressed, but dogs seem to detect it. In this, they have a huge advantage over humans. The nose of a dog has 220 million smell cells compared to a meagre five million in humans.

The powerful sniffers of dogs have long been effective in detecting cancer. A report years ago in the British Journal Lancet reported that a woman's dog repeatedly sniffed at one mole on her thigh but ignored others. When wearing shorts, her dog had tried to bite off the mole. She presented the issue to her doctor. The diagnosis was a malignant melanoma.

We now know that cancers contain alkanes and benzene derivates which are not present in healthy tissue. Scientists have shown dogs can detect either a single chemical or a combination of them.

Bloodhounds have a reputation as the best in tracking down criminals. But other breeds, like poodles, are suited for medical careers. Studies show that dogs are right 99 percent of the time in diagnosing cancer. Another study showed that dermatologists and plastic surgeons were right just 66 percent of the time.

Clara Wilson, a doctoral student at Queen's University, Belfast, School of Psychology, is one of the authors of a new fascinating experiment. She set out to learn if your dog, or in fact anyone's dog, could smell your level of stress.

Wilson collected samples of sweat and breath from 36 people before and after they faced a difficult math problem – with a time difference of just four minutes. Apparently these people were not mathematicians, as the numerical test induced a faster heart rate and raised blood pressure. Four dogs trained in selecting scents from a line-up were then put to the task. The dogs accurately identified the samples taken from "stressed" participants, ignoring the "relaxed" samples from the same person.

"The research highlights that dogs do not need visual or audio cues to pick up on human stress," Wilson explains. "Dogs can smell stress from breath and sweat alone, which could be useful when training service dogs and therapy dogs."

We know that dogs can offer great psychological support to people afflicted with anxiety problems. They also help those recovering from a traumatic injury.

But there are times, such as the death of a loved one, when the degree of stress in a dog's brain is overwhelmingly apparent. For instance, Dave Ross was a police dog handler who lost his life. His German shepherd, Danny, attended the funeral. It was apparent to all that the dog was whining while lying at the casket.

We don't know the nature of that German shepherd's anxiety. But one thing is certain. The dog was not begging for a bone. Man's best friend was hurting.

Future science will dig deeper into the workings of a dog's nose and brain. The foundation for such work has been laid by pioneering scholars like Marc Bekoff, Professor Emeritus of Ecology and Evolutionary Biology at the University of Colorado Boulder. His brain imaging work with animals shows evidence of their abilities to feel grief, fear, love, and compassion.

For now, just know that those 200 million cells in the nose of a dog can tell when you are having a bad day.