Scientists are beginning to realize that having a dog is good for you. Studies by theAmerican Heart Association, Europe PMC and PubMed.gov have shown that having a dog improves blood pressure, lowers cholesterol and helps with depression, anxiety and autism. Researchers have also found that children who grow up in a household with dogs have a lower risk of developing asthma and allergies1. Scientists believe that growing up with a dog exposes a child’s immune system to different antigens (an antigen is any foreign substance that evokes an immune response) and helps desensitize their developing immune system so it doesn’t overreact to harmless environmental antigens, like pollen or grass. Click here to learn more about pets helping with allergies and asthma.
In other words, growing-up around a dog “trains” your immune system so it doesn’t “overreact” to normal environmental antigens. This “overreaction” to normal antigens is the basis for allergies. However, there is evidence that the allergy benefits of having a dog are mediated by exposure to a dog’s microbiome.
What’s a microbiome?
The microbiome refers to the community of microorganisms that coexist in people, animals and plants. Most people are familiar with the use of probiotics to help promote a healthy gut microbiome. “Probiotics” are live cultures of “good” microorganisms, such as Lactobacillus and Bifidobacterium. Interestingly, living with a dog seems to result in a sharing of microbiomes. A study by elifesciences.org reported that families with dogs share as much of their microbiome with their dogs as they do with each other2.
The study of dog germs
This growing body of evidence has prompted researchers from the University of Arizona to design a study to determine if it’s the sharing of a dog’s microbiome that leads to some of the reported health benefits. Led by Dr. Charles Raison3, the study will enroll participants older than 50 years who have not taken antibiotics or lived with dogs for the last 6 months. Lizzie Parry of dailymail.com reports, the participants will choose a dog from the Humane Society of Southern Arizona and live with their dog for 3 months. Researchers will assess the gut microbiome of the participants and their dogs, their diet, level of activity and immune system function at baseline. They will then reassess at the end of month one, two and three. Changes in the mental well-being of the participants and their dogs will also be assessed. These researchers hope to determine if changes in the microbiome of dog owners correlate with improved immune system function and mental health. If their hypothesis proves to be true, your doctor may prescribe a big, sloppy dog kiss rather than an apple a day.
If you have any questions or concerns, you should always visit or call your veterinarian -- they are your best resource to ensure the health and well-being of your pets.
- MacPete, Ruth. "Pets Are Good For Kids!" Our Site. 3 Sept. 2013. Web.
- "Cohabiting Family Members Share Microbiota with One Another and with Their Dogs." ELife. 16 Apr. Web.
- Parry, Lizzie. "Could a Kiss from Your Dog Be GOOD for You?" Daily Mail.com. 19 Mar. 2015. Web.
Are Pets the New Probiotic?
Scientists are paying increasing attention to the “indoor microbiome,” the billions of bacteria, viruses and fungi that we share our homes and offices with. But not all those micro-organisms are bad for us, experts note. And exposure to a rich array of indoor germs may actually be salutary, helping stave off a variety of illnesses.
So there is growing concern that, in our anxiety to banish bacteria from our indoor world, we have become too clean for our own good. We run the risk of scrubbing, disinfecting, vacuuming and filtering out the fortifying mix of microscopic creatures that our immune system needs to develop properly.
Dogs roll in the mud. They sniff feces and other questionable substances. Then they track countless germs into our homes on their paws, snouts and fur.
And if the latest research on pets and human health is correct, that cloud of dog-borne microbes may be working to keep us healthy. Epidemiological studies show that children who grow up in households with dogs have a lower risk for developing autoimmune illnesses like asthma and allergies — and it may be a result of the diversity of microbes that these animals bring inside our homes.
According to the so-called hygiene hypothesis, spending over 90 percent of our time in the bacteria-poor environment indoors, as we do (especially early in life, when our immune systems are being formed), can cause our bodies to overreact to harmless substances later on, making us sick.
“Allergies and asthma are both examples of the way that the immune system is misfiring,” said Jordan Peccia, a professor of environmental engineering at Yale University. “An allergy is our immune system attacking something that it shouldn’t attack, because it hasn’t been calibrated properly.”
Dr. Peccia said exposure to animal micro-organisms during the first three months of life helps to stimulate a child’s immune system so that it doesn’t become overly sensitive later in life. A study published last year in The New England Journal of Medicine found that Amish children in Indiana who grew up close to barnyard animals had far lower rates of asthma than Hutterite children, who were raised apart from animals on large mechanized farms in North Dakota.
A co-author of the study, Jack Gilbert, the director of the Microbiome Center at the University of Chicago, said that the Amish suffer from fewer immune-related illnesses than the rest of us because they grow up with their livestock and the bacteria they host, as our human predecessors did for thousands of years.
When we are deprived of contact with these ancestral bacterial allies, our immune systems sometimes lose the ability to distinguish between friend and foe. The solution: “If we can’t bring our kids to the farm, maybe we can bring the farm to kids,” said Dr. Gilbert, who believes that cohabitation with pets is the next best thing to living next door to a barnyard for training a growing immune system.
Our home environments already contain an abundance of microbes. An analysis of house dust collected by volunteers in a citizen science study called “The Wild Life of Our Homes” found more than 125,000 kinds of bacteria and 70,000-plus species of fungi in the participants’ dwellings.
Each of us sheds 38 million bacteria into our environment every hour. We breathe them out they flake off our skin. Many of those bacteria die right away in the warm, dry air of our homes. But countless microbes survive in house dust or cling to the surfaces of things like computer screens and pillowcases.
Pets, and dogs especially, add a lot to the diversity of the indoor microbiome. Research has shown that dog ownership raised the levels of 56 different classes of bacterial species in the indoor environment, while naturally more fastidious cats boosted only 24 categories. We don’t yet know if contact with feline microbes also helps prevent immune disorders there have not yet been large enough studies to provide reliable data, Dr. Gilbert said. “But we do know that indoor cats have less impact on the indoor microbiome than outdoor cats,” he added.
For sure, some animal-borne microbes are not good for us, said Dr. Scarlett Magda, the president of the New York-based Veterinarians International, a nonprofit group that promotes human and animal health through veterinary care.
Dogs may, for example, lick the urine of rodents infected with leptospirosis, then lick us and transmit the bacteria through breaks in the skin, though only a handful of cases of leptospirosis are reported in New York City each year, and it’s not known if any were caused by pets.
Cats are well-known carriers of toxoplasmosis. And pet turtles and frogs (and occasionally dogs and cats) can carry salmonella bacteria on their skin and in their feces. But not to worry, said Dr. Magda: “Just wash your hands.”
The potential upsides of pet ownership appear to outweigh the risks — and continue to be elucidated.
Some intriguing early research suggests links between the microbes that our animal companions bring into our homes — and that we breathe in and swallow — and the microbes that thrive in our digestive tract. “Exposure to animal bacteria may trigger bacteria in our gut to change how they metabolize the neurotransmitters that have an impact on mood and other mental functions,” Dr. Gilbert said, although he cautioned that research into how pet microbes affect the human gut microbiome remains at an early stage.
Netzin Steklis, a biologist at the University of Arizona who is working on a study of the elderly to learn more about how living with dogs changes their skin and gut microbiomes, says that pet owners have long known that animal companionship can lift our mood. “But it is not just an oxytocin story anymore,” she said, referring to the brain chemical often called the hormone of love. She suspects that the physiological effect of their bacteria in our guts may contribute to the well-known antidepressive benefit of pet ownership.
“Dogs have been with humans for 40,000 years,” she said. “But we are only now looking to find out how living with them impacts our health. We’ll know more soon.”
Could you make each other sick?
Human and dog mouths have “a large number and a wide variety of bacteria,” Fobian says. Fortunately, most of it doesn’t make us sick, but some can. Parasites like hookworm, roundworm, and giardia can be passed from dog to human through licking. Salmonella, too, can be passed from your dog to you, or vice versa.
Viruses tend to affect one species or the other you’re not going to give your dog a cold, and they won’t be giving you their cough.
Does closing schools slow the spread of coronavirus? Past outbreaks provide clues
Q: Can we pass the new coronavirus to our pets?
A: SARS-CoV-2 spreads from humans to humans. There is no research to support human to animal spread at this time. Samples from the Hong Kong dog had a small number of virus particles present. In an animal with no clinical signs of disease, it’s hard to say what this means. It was a single case, and we learned that we need to do a lot more research into the potential of human SARS-CoV-2 to infect animals.
That said, cats and dogs are mammals too. They have many of the same types of receptors on their cells that we do. So the virus could theoretically attach to these receptors. But will it enter their cells and replicate? Probably not.
Still, people infected with SARS-CoV-2 should limit contact with their pets. Wash your hands, and don’t let them lick you on the face. If the virus is in your secretions, and there’s any potential of transmission, these are ways it could be transmitted.
Shelley Rankin is a microbiologist at the University of Pennsylvania School of Veterinary Medicine, Philadelphia.
Q: Should we be testing the pets of people with confirmed cases of COVID-19?
A: That’s [not] everybody’s top priority right now. It should be discussed, however, if we start seeing more cases like the Hong Kong Pomeranian.
Q: Can pets serve as a reservoir of the virus and pass it back to us?
A: If pets can become infected—and we don’t know if they can—then yes, they could serve as a reservoir. And in that case, we’d need to deal with them the same way we’re dealing with human cases. We’d need to figure how to treat them. Like human hospitals, vet hospitals would have to be prepared for a surge in the number of cases.
Q: Would we quarantine our pets too?
A: Yes, just like humans, some might be quarantined at a hospital. Or a shelter. Or even a doggy day care. If they had the virus but weren’t sick, you could quarantine them at home. You’d want to limit your contact with them. Perhaps keep them in a bedroom away from other people and animals. You’d want to wash your hands frequently, and perhaps wear a mask when you entered the room.
Q: If you have people in the same house—some quarantined, some not—can the pet visit both?
A: No. Out of an abundance of caution, the answer should be no.
Q: What should we be doing right now to protect our pets?
A: It is important to include pets in your family's preparedness planning. If you get sick and are quarantined, you should make sure you have extra pet food on hand. And you should make your neighbors aware of any feeding, walking, or medications that your pets need in case you can’t make it back home. Get prepared now. I live alone with my cat. I have extra food on hand. Even if he doesn’t need it [soon], he’s going to eat it eventually.
Dogs Bring More Germs In, But Research Says They Still Make Us Healthier
A new book chronicles the inner workings of our homes, including pets' microbial impact. Luckily it offers good, albeit gross, news.
There are few cliches out there as timeless and true as the one about a dogs' role as man's best friend. If you've ever owned one, you know why. Loyal to a fault and endlessly entertaining, they simply make good company. And as more and more research shows, they not only make for happier homes, but healthier ones.
Science journalist Emily Anthes explores how all the many inner workings of indoor spaces intimately affect our lives in her 2020 book, The Great Indoors: The Surprising Science of How Buildings Shape Our Behavior, Health, and Happiness. This includes pets. It's no surprise to dog owners they certainly affect our behavior and happiness and as a byproduct of those, our health.
But Anthes points to research in The Great Indoors that proves this isn't just about walking more or combating stress. It gets down to the microbes. As a self-professed dog lover, dog owner, and all-around "dog person" myself, even I have had to repress the occasional yet overwhelming "ick" that comes with wondering what all a dog can potentially track in. She looked into it.
The bad news first: Anthes writes that dogs do, undeniably, "introduce their own drool and fecal microbes into a home and track soil dwellers in from outside." (Cue: the "ick". ) Cat people can rest easy Anthes reports that feline friends "change a home's microbial makeup more modestly." They're smaller, they go outside less (if at all), and they don't insist on rolling in that one spot in your neighbor's yard every single time you pass by.
Now, the good news: Anthes later writes, "Studies show that children who live with dogs, which increase the richness and diversity of bacteria in a home, are less sensitive to allergens and less likely to develop asthma." She notes children who grow up on farms and are exposed to livestock reap the same benefits of protection from allergies and asthma too. You know, in case you're looking for a reason to live out your pastoral dreams.
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Want to learn more? The entire book is worth a read to understand how everything from showerheads to modern office spaces affect our well-being.