If fluids can get trapped, then bacteria can grow on the surface. If you share your toys, then you’ll want to consider the cleaning options that sanitize, like boiling for dildos and plugs or 10% bleach solution rinse or alcohol wipe down (unless the manufacturer prohibits it). Vixen, maker of awesome dildos and creator of dual-density Vixskin, kindly tested their items for me with rubbing alcohol. Even a day-long soak in the rubbing alcohol didn’t do a thing to the material. However I have seen other manufacturers specifically warn against it, these are usually the type of silicone vibrators that have a silky-soft feeling and don’t attract dust and fur. Always make sure to read the box/user manual before you clean your sex toy!