The incidence of asthma in youth and children has tripled in the US since the 1970s. Researchers argue over whether improved modern hygiene practices, increasing use of antibiotics (especially in food), reduced physical activity, and even global warming are to blame. Everyone does agree, however, that since this occurrence has happened within 2 generations, genetic evolution is highly unlikely. It’s something humans are doing differently, it seems, but what?
Pet owners (and the housekeepers who tend to their indoor habitats) will not be surprised to learn that cats and/or dogs in the home increase the diversity of the microbiota of the home. In other words, there are more types of germs. But did you know that the stool microbiota of children living with pets differs from those without pet exposure? There is more zoo in their poo. Studies in homes of farmers find an even broader diversity of microbes (that would be me). And, hooray! Several investigations have found that farm living leads to a lower prevalence of allergic disease as well. One important factor in farm living is the consumption of unpasteurized milk (again, me). The hypotheses are that farm milk contains many live bacteria that can alter human gut microbiota, that unpasteurized milk contains substances supporting the growth of specific beneficial microbes, or both simultaneously.
It seems that exposure to diverse bacteria must occur during the first year of life for significant immune response impacts, and perhaps in the first weeks of life! The types of bacteria which appear to be protective are bacteria found in the gastrointestinal tracts of mammals. Emerging evidence of the power of dirty things has led some experts to suggest that health advice for parents shift from the “hygiene” to the “microbial” hypothesis of allergen protection.
My personal experience with cats began as a newborn. We had a beloved calico that slept with me continually. Oddly, as a young adult, I developed asthma-related symptoms due to allergies to most grasses found in the area, as well as cats. This definitely defies the logic stated above. However, I found that all symptoms experienced in my 20’s were gone by my 30s. Was my immune system challenged enough, even though an adult, that I grew de-sensitized (because as so many pet owners do, I refused to give up my cat). Would my allergies have been 10 times worse without such exposure as a child? Hard to say, but fun to speculate on.
Anyway, the abstract for one of these studies is included here and the link for the whole study is pasted below that.
“Allergic reactions to pets have been recognized for at least a hundred years. Yet our understanding of the effects of all of the interactions between pet exposures and human immune responses continues to grow. Allergists, epidemiologists, and immunologists have spent years trying to better understand how exposures to pet allergens lead to allergic sensitization (the production of allergen-specific immunoglobulin class E [IgE] antibodies) and subsequent allergic disease. A major new development in this understanding is the recognition that pet exposures consist of not only allergen exposures but also changes in microbial exposures. Exposures to certain pet-associated microbes, especially in the neonatal period, appear to be able to dramatically alter how a child’s immune system develops and this in turn reduces the risk of allergic sensitization and disease. An exciting challenge in the next few years will be to see whether these changes can be developed into a realistic preventative strategy with the expectation of significantly reducing allergic disease, especially asthma.”
Wouldn’t it be funny if one day your doctor advises you to engage in a round of ‘furroma therapy’ to improve your asthma!
Please feel free to comment on personal experiences with this human-animal bond topic. Always welcomed.