There are some who link prophylactic use of antibiotics during delivery (birth) for those who are GBS+ (a kind of bacteria that can be in the colon and, in rare cases, can cause serious illness in newborns--so many doctors just have all their GBS+ patients pumped with IV antibiotics while in labor as a preventative) to a higher incidence of peanut allergies. Killing off the good bacteria in the gut when first exposed to the world could be causing some of this mayhem. We had a serious discussion about this with our pediatrician when I chose to go against the grain and not have the antibiotics with my son. We had to agree to 48 hrs observation post-delivery, but he was cool with it. And since birth, he has been healthier than his older sister, with whom I did have the prophylactic antibiotics.
Incidentally, this practice came into play in the early 90s, and the rise in peanut allergies came around the same time.