Dogs, Us & Microbes - Lots Of Good News !!

• In one study in Detroit, the health of pregnant women (and their newborns) with dogs in their homes was compared to that of those who did without. Researchers examined the effect of having a dog on one indicator of an individual’s tendency to develop allergies: the level of IgE antibodies in the mother’s umbilical cord blood. What these researchers found: pregnant mothers who lived in houses with dogs tended to have lower levels of IgE antibodies in their cord blood—and such lower levels have been found to be protective when it comes to childhood allergies. This study like any study, had limits. The number of women considered was relatively small. In addition, the study was not experimental. The dogs were not given randomly to women irrespective of their interest in having a dog. 
• The researchers studying pregnant mothers posited that the effect of the dogs is due to the effect of dogs on the microbes in the house and on and even in the body. Initially, this argument was pure speculation, but in 2010 another group of researchers considered the microbes in six houses with dogs and five without. Their goal was specific, figuring out which microbes were present. They seemed to find a difference, though they were appropriately cautious in interpreting it, stating that the diversity of bacteria in the dog houses seemed higher than that in the no-dog houses. Interestingly, fungal diversity seemed lower in dog houses (though again, the sample size was very small).
• A more recent study has shown that children with pets in general (primarily dogs) are at a reduced risk of childhood wheezing (which is associated with allergy and asthma). The study also found that one common bacteria species, generally thought of as a beneficial gut microbe, Bifodobacterium longum, was more abundant in those children exposed to pets than those who were not exposed to pets and suffered from wheezing.
• I’ll suggest a hypothesis for just what it is that our dogs are doing in our homes. Once, our dogs were our mutualists. We benefited them and they us; today our relationship is more complex. But I hypothesize that our dogs still affect our fitness. They do so when they bring bacteria to us. They bring it in their mouths, on their skin and in their fur, but also  from the dirt around our homes (this much is not speculative, it now seems well-supported). I hypothesize that some people, particularly a subset of individuals living in very urban environments, environments in which their fingers rarely sink deeply into the mud, are so deeply removed from the diversity of wild species that their immune systems fail to develop normally (this also seems rather well supported). Finally (this is the bit in which I lean out into the darkness and wave my hands), I hypothesize that in these latter settings, settings like those found in many suburbs and most cities, dogs reconnect us to a diversity of species, species they drag into our houses, species that in the absence of more robust connections to microbial diversity may be sufficient to bring sense to our immune system. The connection dogs offer is not perfect (we might achieve a similar effect, other studies suggest, by living on a farm, or even planting native species in our backyards), but it can sometimes be enough in a world in which we have so few direct connections to life’s richness. In other words, while our dogs sometimes bring us frozen turkeys, they may,other days, bring us health. 

 - More Here from Rob Dun, author of The Wild Life of Our Bodies: Predators, Parasites, and Partners That Shape Who We Are Today

Btw., I am still waiting for my results from his Wild Life In Our Homes Project