Pets and your child’s immune system

I’ve said time and time again that solid science does not come from individual studies sitting all by their lonesome. Rather, it comes about as a result of a body of evidence. That isn’t to discredit any individual study that may be released, but instead to point out that the very nature of science is to discover and expose and correct for flaws. That cannot possibly be accomplished if one person or group comes up with a finding and everyone says, ‘Oh, good. Let’s just go with that.’ And that brings me to this recent study on children who live with dogs in their first year of life:

The study of nearly 400 children found that dogs were especially protective, and the babies who lived with dogs during their first year were about one-third more likely to be healthy during their first year, compared to babies who didn’t have a pet in the home. Babies with dogs in the home were 44 percent less likely to develop an ear infection, and 29 percent less likely to need antibiotics than their petless peers.

“Children who had dog contacts at home were healthier and had less frequent ear infections and needed fewer courses of antibiotics than children who had no dog contacts,” said the study’s lead author, Dr. Eija Bergroth, a pediatrician who worked at Kuopio University Hospital, in Finland, at the time of the study.

There is no reason to doubt the methodology of this study, as far as I know. There is no reason to doubt its integrity. This isn’t a highly complicated paper about kin selection or something of that nature where the logic can get quite counter-intuitive. This is a relatively straight-forward study, by all accounts. However, that does not mean it actually is better to have dogs around infants:

Previous research on pets in the home has suggested that animals, and dogs in particular, may provide some protection against the development of asthma and allergies. But, other studies have found that household pets may increase the number of respiratory infections in children, according to background information in the study.

Yet, on the flip side once again, this doesn’t mean it’s bad to have dogs (unless the child has allergies, of course). What this means is that there are some interesting results, both of which fit well into independent theories. For the previous studies, we know that animals carry plenty of germs and disease, so it wouldn’t be surprising to learn that they tend to transmit that sort of stuff to babies – basic germ theory. However, for this recent study, we also know that the immune system tends to do better when exposed to diverse environments early in life. That gives it a chance to build a working ‘knowledge’ of what it must resist. So which is the correct model?

We don’t yet know.

I personally lean towards it being better to have pets in the home, in part because dogs and cats are linked to greater happiness, which in turn is linked to a healthier body, but I’m not staking a claim to anything one way or another. The scientifically responsible thing to do here is to wait for a more robust body of evidence.

That’s how this whole thing works.