Peanut allergies have plummeted in children(nytimes.com)

  In the U.S., the rate of childhood peanut allergies more than tripled between 1997 and 2008. 

  ...

  In fact, the American Academy of Pediatrics issued a (now-outdated) recommendation in 2000, which directed parents to avoid feeding baby peanuts until they reached the age of three, especially if a baby was at high risk for a peanut allergy.

  But when these recommendations to delay feeding peanut were introduced, there was no study to support these recommendations. Rather, they were just based on physicians' guesses.

  As Dr. Spergel explains, "Back then, we gave people really bad advice. We told people to avoid food allergens... But there was never any evidence for this. It was just based on a few physicians’ best guess. There's never been any study that ever proved that food avoidance worked. "

  Today, we know that this approach to delay peanut introduction actually increases food allergy risk, and that delayed introduction was a major factor that led to the sharp increase in peanut allergies.