地平线之过敏症·现代生活和我

　　Changes to the bacteria that live inside all of us are responsible for increasing the number of people with allergies, suggests new research.
　　In this episode of Horizon, the show investigates this claim by conducting a unique experiment with two allergic families in order to find out just what it is in the modern world that is to blame. With a raft of mini cameras, GPS units an...