Don't let Mr. Peanut's top hat and monocle fool you — beneath that gentlemanly exterior lies one deadly little nut if you're one of the roughly 1% of the population that has a peanut allergy. It's the most common cause of food-allergy deaths, according to the American Academy of Allergy, Asthma and Immunology. And for little understood reasons, it's on the rise. From 1997 to 2002, incidents of peanut allergy doubled in children.