Of course we wash our hands after using the restroom, but how we dry them determines whether bacteria die off or thrive and spread, according to a new study in the Journal of Applied Microbiology. Researchers measured the number of bacteria transferred from hands to other surfaces after volunteers washed and then used different types of electric hand dryers like the ones found in many public restrooms.

Most hygienic: High-velocity air-jet electric dryers that quickly strip water away while hands are held still.

Less hygienic: Conventional warm-air hand dryers, which work by evaporation.

Reasons: When hands are rubbed together (as they usually are to hasten drying with these machines), bacteria that live in the skin can be brought to the surface and then transferred to other objects… and people often are too impatient to dry hands thoroughly with these slower machines, so the remaining moisture allows bacteria to move more readily from one surface to another.

Bottom line: Hand drying is an important part of hand hygiene, not a mere optional step after washing. Take time to dry hands thoroughly, no matter where you are or what method you use (including paper or cloth towels), so you’ll be less likely to spread any bugs that survive the soap and water—and less likely to pick up new ones from whatever you touch next.