It's possible to escape some tree and weed allergies by moving to a new town, state or region, and the same may be true of dust-mite allergies. The microscopic arachnids—which leave behind feces and corpses that can trigger allergic responses and asthma—are sparse across large swaths of the Great Plains and Mountain West, according to a new survey of the arthropods that inhabit our homes.

With the help of citizen scientists, researchers from North Carolina State University and the University of Colorado Boulder analyzed arthropod DNA found in 732 dust samples collected from interior door frames throughout the U.S. Amid their data on many other species, the scientists found that the eastern U.S. and the West Coast are dust-mite utopias, whereas much of the western interior may be a comparative desert. Why? Because mites need high humidity to survive. (They cannot drink; instead they absorb moisture from the air to stay hydrated.)

Lead author Anne Madden cautions that just because samples from parts of the West tested negative for dust mites, it does not mean those areas are devoid of the critters. Even in dry regions, mattresses and carpets—as well as furniture moved from humid areas—may harbor dust-mite colonies, says David Miller, who studies the links between damp housing and health at Carleton University in Ottawa and was not involved in this study.

An estimated 20 million Americans suffer from allergies to these tiny creatures. “If you're allergic to dust mites, living in dry-land America and Canada and in high elevations is absolutely a good thing,” Miller says. But you don't have to move across the country to escape: encasing mattresses and pillows in allergen-proof covers, laundering sheets once a week and vacuuming frequently with a machine fitted with a HEPA filter will help banish the bugs.