Allergies and asthma have been on the rise in the US for quite a while and figuring out which factors play a role has been a major push in research. The hygiene theory has been on the table for several years now and goes something like this: because our society has become so clean and sterile, our bodies aren’t used to coexisting with anything and when it gets exposed to something new, it overreacts in the form of allergic inflammation. When we all used to live on farms and got exposed to a bunch of animals and their fur and poop and hay and dirt and everything else that goes along with growing our own food, when we didn’t have pristine water supply and we all breastfed until we were at least a year old, we were coexisting with all sorts of different bacteria and allergic disease was at a minimum.
The hygiene theory may not answer everything and of course having clean water and not eating dirt has indeed resulted in other significant health benefits and decreased other disease significantly, but interesting new research lends more credence to the idea that we may need to live in more natural balance with the bacterial flora of our world to minimize allergic disease.
The most recent support for this idea is that babies born by C-section seem to have a significantly higher likelihood of going on to have allergies and/or asthma than babies born vaginally. By forgoing a trip through the birth canal it seems these babies miss an opportunity to get colonized by the bacteria of the vagina and perineal area. Babies born vaginally get colonized and these bacteria then go on to multiply and begin to take up residence in the body of the newborn. This coexistence may indeed be essential to immune system tolerance and the absence of it may predispose the immune system to overreact to exposures later on.
Most of the time when women have C-sections, it’s because either their life or the baby’s is at risk. Worrying about allergy or asthma pales in comparison to that, but if a woman is considering an elective C-section for convenience, I think serious thought should be given to the consequences of missing the opportunity to colonize the newborn with flora that may be protective in the long run.