The Many Health Benefits of Your Pet’s Bacteria

A growing body of evidence is finding a microbial advantage to owning pets, especially in childhood, adding to other health benefits of animals.

Dogs and other animals trade microbes with the people living in their homes. Shutterstock

Dogs harbor more than 600 different bacteria in their mouths alone, making every lick and slobber a potential human health risk.

Just like humans, pets have a microbiome—communities of bacteria, fungi, and viruses—not only in their mouths, but also on their skin and in their stool. Although only 16.4 percent of dogs’ oral bacteria are also found in humans, it’s apparent that we swap microbial critters with them just like we do with members of our family.

In Favor of Pets

Nearly 45 percent of U.S. households have a dog, and 25 percent have a cat, according to the American Veterinary Medical Association.

Previous studies have found that pets can reduce stress, prevent heart disease, and lower the risk of high blood pressure, depression, asthma, allergies, and obesity. The microbial connection strengthens the argument that animals can be good for human health.

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A 2024 review in Research in Veterinary Science noted that our relationship with pets generally causes homeostasis in both human and animal microbial patterns. Microbial homeostasis indicates that the balance of microorganisms living in one’s gut is favorable for preventing an overgrowth of disease-causing bugs.

“As a result of keeping pets, the microbiota of different areas of the human body has changed, which has been associated with a decrease in pathogenic bacteria and an increase in beneficial bacteria,” the study authors concluded.

Possible Explanation

Microbial benefits conferred to humans from their furry companions were discovered in a May study published in Clinical Gastroenterology and Hepatology. Researchers were examining possible environmental triggers among 4,289 relatives of patients with Crohn’s disease to see what might make them more or less susceptible to developing the disease themselves. Crohn’s disease is a type of inflammatory bowel disease that can affect any level of the digestive tract.

What they found was that dog ownership increased the relative abundance and diversity of gut bacteria.

Diverse and abundant microbial communities in the human gut are associated with health benefits, including protection against pathogen-driven illnesses and disease.

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“It’s critical to know that [this finding] doesn’t mean dogs will prevent disease,” said William Turpin, co-author of the study that is part of the ongoing genetic and environmental microbial project. “It’s not a cure. It’s just an association. We need more studies to verify whether this is truly a factor.”

Those participants who owned dogs at the time of the study or had dogs early in life also had less inflammation in biomarker testing and tighter intestinal junctions. Loose junctions are associated with altered intestinal permeability and gastrointestinal (GI) illnesses.

Exposure to dogs was found to be protective in all age groups and regardless of how old participants were when they owned the dog. However, the strongest association of reduced exposure was in the 5-to-15 age group.

Having a dog was “the most robust association with the reduction of Crohn’s. We tried to be as broad as possible ... and we included many different environmental factors and a lot of different animals,” Turpin told The Epoch Times.

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The findings could have implications for other GI conditions, Turpin said, such as irritable bowel syndrome and celiac disease. Both have been associated with similar patterns of low microbial diversity and gut permeability.

“It is possible that this discovery of dogs decreasing those risk factors may be relevant to other GI diseases,” he said.

Animals Shedding Microbes

Laurel Redding, associate professor of epidemiology at the University of Pennsylvania School of Veterinary Medicine, noted a growing body of research showing young children exposed to farm animals or house pets tend to have richer and more diverse gut microbiomes.

Disease-causing microbes tend to get a lot of research and media attention, Redding told The Epoch Times. More than 60 percent of known human infectious diseases are capable of being spread from animals, and 75 percent of new or emerging human infectious diseases originated in animals, according to the Centers for Disease Control and Prevention.

“The focus in the past has tended to be on what we share with animals that’s bad, and there is a decent amount of microorganisms we share that are bad,” Redding said. “More recently now, we’re trying to focus on what we share that’s good. There’s been a lot less research done on this, and that’s one of the things I’m hoping to change.”

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She said that people can have bacteria and other microorganisms transferred from pets in a home by petting the animals or being licked; changing litter boxes or cleaning up animal feces; and inhaling dust from dander or fecal matter.

People can also transfer their microbes to pets, she added. Redding was among a group of researchers who wanted to learn whether this exchange could contribute to the recurrence of Clostridium difficile (C. diff) infections, which cause diarrhea, fever, nausea, dehydration, stomach cramping, and loss of appetite.

Protection Against C. diff

The most common cause of infectious diarrhea in health care settings, C. diff infections are often associated with recent antibiotic use. Antibiotics often wipe out health-protective bacteria and leave a person’s immune system compromised and vulnerable to more infections. The elderly and children, as well as those who were recently hospitalized, are more at risk of C. diff infections.

Redding and a team of researchers originally thought that pets could be a reservoir for C. diff. In other words, they believed it was possible that those struggling with C. diff could pass the infection to their pets, which could shed it back into the environment and make pet owners sick after their initial recovery.

“What we actually found was the opposite. People who had pets were protected, or less likely to have recurrence of C. diff infection,” she said.

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Although the finding was surprising, Redding said it was validated by a “dose-response effect,” meaning the more exposure, the greater the benefit.

“The more contact you had with your pets, so if you let it sleep on your bed and let it lick your hands and face, you were even better protected than someone who didn’t. That was a really interesting and unexpected finding,” she said.

Redding is continuing to explore the mechanism at work. The results raise the question that pets could be restoring protective microbes to their owners’ microbiomes that help them keep C. diff from causing symptoms, she said. C. diff can be found in healthy subjects.

Redding published another study in 2023 involving C. diff and pets that determined whether pet owners and animals were passing the bacterium back and forth. In 47 households, C. diff was detected in 30 humans, 10 dogs, and zero cats. Of those samples, the same strain was found in only one household, suggesting that C. diff is rarely being transmitted between people and pets.

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Nevertheless, animal-to-human transmission of C. diff is possible. A case study published in 2022 in Anaerobe found a 10-month-old baby became ill with the identical C. diff strain as a dog in the home that had chronic diarrhea.

Love Pets With Caution

Redding said those who have weakened immune systems because of certain diseases, such as diabetes or autoimmune conditions, as well as those taking certain medications, should be especially vigilant to avoid the spread of disease from their pets.

A 2024 review on the impacts of dogs’ oral microbiota on human health offered these suggestions for protecting yourself from pathogens around your pet:

• Regularly wash your hands.
• Remove and throw away dog feces using gloves or plastic bags.
• Stay away from areas that may be contaminated with dog feces.

Redding added that if you feed raw food to animals, be sure to frequently wash your hands and their feeding bowls.

“There’s always going to be a fine line between the risks and the benefits. At this point, we really don’t know where that line is,” she said.

“Certainly, there’s hope that pets can be microbiologically beneficial to us in addition to the psychosocial aspect.

“So yeah, hug your pets, but wash your hands after.”