I share the same wonderment! In the 20 years of growing up in Kenya, I had never heard of anyone with allergies. I am baffled about how widespread allergies are in the US. Could the prolonged use of germ-killing products in the US cause this disparity? Unfortunately, I do not have statistics on allergy prevalence in Kenya vs. USA, and my wonderment is based simply on observation/experience.

[Edit]. The Hygiene Hypothesis (http://en.wikipedia.org/wiki/Hygiene_hypothesis): "In medicine, the hygiene hypothesis is a hypothesis that states that a lack of early childhood exposure to infectious agents, symbiotic microorganisms (e.g., gut flora or probiotics), and parasites increases susceptibility to allergic diseases by modulating immune system development"

[Edit2]. Statistics on the prevalence of allergies in the US: http://aaaai.org/media/statistics/allergy-statistics.asp