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I think one of my favorite blog posts I’ve written was about why dogs and kids are so great together. In this post, I mention the hygiene hypothesis, which suggests that the increasing prevalence of allergies in our society might be due to us being too clean.
There have been a few studies coming out recently that support this theory, that pet-owning households may have less-sick children than households without pets. One study saw that infants who had contact with dogs had a lower incidence of becoming sick or were sick for a shorter period of time, compared to children who did not have contact with dogs (and this includes children who had contact with cats. Take that, Some-Famous-Random-Cat!).
While this study in and of itself doesn’t definitively say that dogs keep babies healthy, it is supported by another recent study. In this set of experiments, researchers fed mice some dust from homes with dogs.  These mice were infected with Respiratory Syncytial Virus (RSV), a common childhood pathogen that causes respiratory infection. Mice exposed to the dust did not have symptoms of RSV disease that were prevalent in the non-dust-eating mice.  In addition, the microbial flora (that is, all the little single-celled critters that live in or on us) in the guts of the dust-eating mice were different than the normal-food mice (note: all the mice ate regular food too, I’m just looking for cute/clever ways to differentiate the two groups). This could be a mechanism to explain the protection found in the dog-dust mice: a different microbiome may result in changes to the immune system that help provide protection.
Even taken together, these studies don’t conclusively say that dogs protect babies from respiratory problems, such as allergies and asthma. The results in the first study might be due to differences in care between the study subjects, or other variables in the study besides dog ownership. In the second study, the researchers omitted a control group of mice eating dust from a dog-free home. This makes it difficult to pin any improved immune responses against RSV directly on dog dander.  This is similar to how vaccines work: we prime the immune response to react a specific way, so when it sees a foreign invader for real, it knows what to do and can act before disease develops.
Moral of the story: while it’s possible that dogs (and to a lesser extent, cats) can cause changes in the immune system that may prevent allergies or certain respiratory infections, there still isn’t any conclusive data. However, having a dog around a home with a familial history of allergies isn’t necessarily going to doom a baby to a lifetime of runny noses and itchy eyes.
And in our home, that’s reason enough to celebrate.
Related articles
Exposure to Dogs Could Protect Kids From Asthma (wired.com)
Pet dogs can help prevent childhood asthma (thesciencebulletin.wordpress.com)
Dog-associated house dust protects against respiratory infection linked to asthma (eurekalert.org)
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