Hi Everyone!
Very interesting topic indeed!The inputs are great!Just let me share my experience and point of view as one of the not so rich countries.
I can relate greatly to the Acquired Immunity explanation. I came from the Philippines and most of the children here including me spent childhood playing outside, exposed on the environment that I cannot guarantee always to be clean. As kids we don't really care since it was the only way we thought then of having fun. During that period I was still very sensitive on the foods I eat since I easily got sick but then after sometime in my teenage years I stopped being sick and was already able to eat all kinds of food with no allergic reactions up to this date. I have also known locals and even friends of mine that were originally allergic to chicken and seafoods that consumed such foods in small quantities. and after sometime, was able to consume it already with large quantity with no more allergic reactions. Although, I have not found a scientific study yet proving enducing small quantities of such allergic foods can cure or develop immunity for such allergic reaction.
Best Regards,
Joven