Katie Wu is a cat person. She has two of them: twin boys named Calvin and Hobbes. But up until grad school, she couldn't be anywhere close to a cat without her throat tightening and her nose clogging up. In a stroke of luck, Katie's cat allergy suddenly disappeared. The reasons for her night-and-day immune overhaul remain a mystery.In this episode, Katie walks host Aaron Scott through the dynamic world of allergies and what it reveals about our immune systems. Calvin and Hobbes make cameo appearances.