The Scientist: Leah S. Millheiser, MD, FACOG, clinical assistant professor in the Department of Obstetrics and Gynecology and director of the Female Sexual Medicine Program at Stanford University Medical Center.
The Answer: Most STDs can't survive outside the body for very long. That said, you should never assume that if you wait long enough, they'll disappear. Everything from HPV to gonorrhea, chlamydia, and HIV can be transferred by sharing sex toys. Even bacterial vaginosis, which isn't an STD but rather just an infection (that can cause serious itching) linked to an imbalance of bacteria in the vagina, can be transferred on your toys. And, if bodily fluids or blood are on the toy, syphilis and hepatitis C can be transferred, too. Scary stuff!
The good news is that if you simply clean your gadgets after each use, you don't ever have to worry about giving or getting something gross. Washing (the good, old-fashioned way, with soap and hot water) is all you really need to do. If the whole toy can't be submerged in water (because of batteries), simply remove and clean whatever parts come into contact with your skin and body fluids. Just make sure to be thorough, so that no tiny particles are left in any of the cracks and crevices. If the toy is made of silicone, you can even throw it in the dishwasher (if it doesn't weird you out to have your vibrator chilling next to your coffee mug, that is) or throw it in a pot of boiling water for five minutes.
Toys that are inserted inside the vagina carry the greatest risk for transferring infections. To protect yourself better, put a condom over the toy and just throw the condom out after. There's no need to throw away your sex toys — regularly replacing them would get expensive — as long as you keep them clean.