Plastic wrap and dental dams prevent transmission of HIV and STIs when used for oral-vaginal or oral-anal sex. Dental dams are latex squares available in medical supply stores and from some adult shops that often come in a variety of flavors. Plastic wrap is also effective in protecting against transmission of HIV and STIs. Be sure the dental dam or plastic wrap covers the entire vulva (clitoris and vaginal opening) and that you hold both edges so the barrier stays in place. Be careful not to turn the dental dam or plastic wrap inside-out while you use it, and never re-use a dental dam or plastic wrap.