If you’ve ever experienced watery eyes, sneezing, runny nose, itchy throat, and other allergic reactions during springtime, or you haven’t but you know someone who has, this beautifully animated TED Ed by Eleanor Nelsen will help explain what’s going on within our immune systems: Why do some people have seasonal allergies?

Next: Cell vs. virus: A battle for health, The benefits of a good night’s sleep, and What are those floaty things in your eye?

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