We have long known that we can catch germs while traveling. Recent years have shown that we can also bring home bed bugs. This holiday season, a PLoS One study informs us that by merely plopping into the seat of a car or airplane, we can unknowingly pick up dust mites—microscopic 8-legged arthropods that eat the dead parts of our bodies such as skin scales, dandruff flakes, and hair. Dust mites are eyeless, headless, and heartless, yet they’re expert travelers. They’ve been trekking around the world for 400 million years; in the modern era, they travel fast and in style, stowing away inside our seat cushions, luggage, and clothes. Although dust mites don’t directly harm us, they trigger allergies in about a billion people. But we aren’t allergic to the buggers themselves. We’re allergic to their poop.