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Study Proves Dog Kisses May Actually Boost Your Immune System

| Published on March 26, 2015

We all know dogs are therapeutic to the soul, but what about to your immune system?

When we were little, our mothers always told us “dog mouths are dirty.” But then another school came along and said that dog’s mouths were actually cleaner than humans. And then that was refuted by science.

But could those germs be good for you?

This video describes a new study that will be conducted by researchers at the University of Arizona to understand whether dogs might improve the lives of older adults on a biological level.

The researchers at the University of Arizona are recruiting participants to find out. The study will explore whether “dogs can improve human heath by having a probiotic effect on the body. The research will focus specifically on dogs’ effect on the health of older adults.”

“We’ve co-evolved with dogs over the millennia, but nobody really understands what it is about this dog-human relationship that makes us feel good about being around dogs,” said Kim Kelly, an anthropology doctoral student and one of the primary investigators on the study. “Is it just that they’re fuzzy and we like to pet them, or is there something else going on under the skin? The question really is: Has the relationship between dogs and humans gotten under the skin? And we believe it has.”

Kim Kelly and her dog Katie Image source:
Image source:

What They Hope to Prove

The human digestive system is home to more than 500 different types of bacteria, both “good” and “bad.” Probiotics often are called “good” or “helpful” bacteria because they help keep the intestines healthy and assist in digesting food; they also are believed to help the immune system. Foods such as yogurt, as well as supplements, can help enhance probiotics in the body.

Kelly, along with her collaborators in the UA Department of Psychiatry, the UA Norton School of Family and Consumer Sciences, the UA School of Animal and Comparative Biomedical Sciences, and the University of California at San Diego, will explore whether living with a dog encourages the growth of positive microorganisms in the human gut — enough to improve physical and mental health in older adults.

“We essentially want to find out, is a dog acting like yogurt in having a probiotic effect?” said Kelly, who also is a principal research specialist in the Department of Psychiatry and program coordinator for the Human-Animal Interaction Research Initiative.


Could your dog's kiss be making you more healthy? Image source: @Eric.Ray via Flickr
Could your dog’s kiss be making you more healthy? Image source: @Eric.Ray via Flickr

Existing research shows that dogs and their owners share much of the same gut bacteria over time. In addition, some studies have shown that dogs enhance immune functioning in children, reducing the risk for immune disorders, such as asthma and allergies.

“We think dogs might work as probiotics to enhance the health of the bacteria that live in our guts. These bacteria, or ‘microbiota,’ are increasingly recognized as playing an essential role in our mental and physical health, especially as we age,” said Dr. Charles Raison, principal investigator for the study and a UA professor of psychiatry in the College of Medicine.

“We know that not all bacteria are good. We can get very sick from the ‘bad’ bacteria, and modern medicine has done a wonderful job of protecting us from various diseases that are created by these bacteria,” said Raison, also a professor of family and consumer sciences. “But unfortunately, by eliminating the bad bacteria we’ve started eliminating the ‘good’ bacteria, too.”

Participants Needed – (You’ll be given a dog!)

Want to be involved? They are looking for participants!

Participants in the study, which is being conducted in partnership with the Humane Society of Southern Arizona, will be paired with a canine companion from the humane society and live with the dog in their home for three months.

At the beginning of the study, researchers will non-invasively evaluate the human participants’ gut bacteria, diet, physical activity levels and immune function. The dogs’ gut bacteria and physical activity levels also will be measured via non-invasive means. Follow-up evaluations will take place after one, two and three months to look for any positive impacts on gut microflora in either the humans or the dogs. Researchers also will note any changes in the mental health and emotional well-being in both the humans and the animals.


If nothing else, we are sure these participants will be in better moods. Who wouldn't be after getting a kiss from a dog? Image source: @TonyAlter via Flickr
If nothing else, we are sure these participants will be in better moods. Who wouldn’t be after getting a kiss from a dog? Image source: @TonyAlter via Flickr

Study participants must be age 50 or older, in good general health, not have taken antibiotics in the past six months, and not have lived with a dog for at least six months. Participants will be able to identify what type of dog they would like and will be able to adopt the dog at the end of the study, but that isn’t a requirement for participation. Food and veterinary care for the dog will be provided during the study period.

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