Bacteria often get a bad rap. We think of them as “germs” that cause disease. We are surrounded by soaps and other products that promise to kill “99.9% of bacteria,” and we try hard to keep our environments as clean as possible. This reputation is not entirely unearned, as bacteria can cause serious diseases in humans and our animal companions. But we are beginning to understand that these “bad bugs” are the minority, and that we live happily and healthily with a vast ecosystem of bacteria and other microorganisms in our surroundings and in our own bodies.
What is the microbiome and why is it important to our health?
The bacterial ecosystem living on and inside of us is called our microbiome. This microbiome is crucial to our health, producing nutrients, protecting us from disease-causing bacterial cousins, and can even modify our immune systems to prevent allergies and other immune disorders.
The specific makeup of our microbiome is affected by genetics, age, diet, and exposure to people, animals, and other environmental influences. Members of each species have broadly similar microbiomes, so humans share more types of bacterial partners with each other than with other species. As individuals, we tend to harbor types of bacteria that are more similar to our relatives or the people we live with than the bacteria of unrelated strangers. However, studies have also shown that people who live with dogs share elements of their microbiome too!
Animals have shared, protective bacteria ecosystems
Humans and dogs living together typically only share a small number of their microbial partners. However, the interactions between our microbial ecosystems may still be quite impactful. For one thing, humans in industrial societies often have a very sparse microbiome, without much variety compared to other animals or to humans in more agricultural settings. After all, we deliberately try to kill off our bacteria and those around us every day! Living with dogs seems to improve the diversity of our microbial partners a little, which might have some positive effects.
A rich diversity of microorganisms in childhood has also been shown to reduce the risk of asthma and allergies as adults. One important element to this protective microbiome is—you guessed it—our dogs!
Microorganisms impact our allergies and our immune systems
The science exploring risk factors for allergies is complex. However, multiple studies have found that exposure to dogs in childhood seems to protect us against developing environmental allergies and asthma later in life. One theory is that dogs increase our exposure to a variety of microorganisms and other possible allergens from the environment. If exposed in our youth while our immune system is still developing, this might train that system to avoid overreacting to things that could otherwise be a trigger for allergies later.
Of course, sometimes our dogs can expose us to the “bad” bacteria too. One of the reasons vets and public health experts recommend not feeding raw meat to dogs is that bacteria in uncooked meat can make our dogs and their humans sick.
There are other possible risks from bacteria our dogs might share with us, especially as we age and our immune systems weaken. But most of the evidence suggests that our dogs are much less likely to transmit infectious bugs to us than other humans. And it may even benefit our health to share some of our canine companion’s microbiome, especially as children.
So what does this mean for us dog owners? We should continue to take basic precautions to avoid “bad bugs.” The CDC recommends washing your hands after playing with your dog, feeding them, or cleaning up after them. Making sure your pet stays healthy, with regular veterinary checkups and preventative treatments, is also important. But there is plenty of evidence that our dogs are good for our health, and anyone who tells you cuddling with your dog is “unsanitary” isn’t keeping up with the science!
Sources
Wetzels, S.U., Strachan, C.R., Conrady, B. et al. Wolves, dogs and humans in regular contact can mutually impact each other’s skin microbiota. Sci Rep 11, 17106 (2021).
Song SJ, Lauber C, Costello EK, et al. Cohabiting family members share microbiota with one another and with their dogs. Elife. 2013;2:e00458. Published 2013 Apr 16. doi:10.7554/eLife.00458
Misic AM, Davis MF, Tyldsley AS, Hodkinson BP, Tolomeo P, Hu B, Nachamkin I, Lautenbach E, Morris DO, Grice EA. The shared microbiota of humans and companion animals as evaluated from Staphylococcus carriage sites. Microbiome. 2015 Jan 23;3:2. doi: 10.1186/s40168-014-0052-7. PMID: 25705378; PMCID: PMC4335418.
Gao X, Yin M, Yang P, Li X, Di L, Wang W, Cui H, Yan X, Liu J. Effect of Exposure to Cats and Dogs on the Risk of Asthma and Allergic Rhinitis: A Systematic Review and Meta-analysis. Am J Rhinol Allergy. 2020 Sep;34(5):703-714. doi: 10.1177/1945892420932487. Epub 2020 Jun 20. PMID: 32564683.
