Do mattress encasements actually stop bed bugs?

Encasements don't kill or repel bed bugs, but a fully zippered six-sided encasement with a sealed zipper traps any bugs already inside the mattress and prevents new ones from harboring there. Specialist communities like r/Bedbugs are explicit that an encasement is a tool inside a broader treatment plan, not a standalone fix. Look for products that explicitly state lab testing against bed bug entry/escape.