A barrier garment apparatus and methods of its use are provided. In an embodiment, the barrier garment apparatus is shaped like an undergarment and worn during oral-vaginal and/or oral-anal sex to protect another person's mouth, lips, tongue, saliva, nose, and breath from contact with the wearer's vulva, perineum, anus, and surrounding areas, in order to prevent the transmission of bacteria, sexually transmitted infections, fluids, tastes, and scents. The barrier garment apparatus is thin, substantially non-porous, elastic, effectively skin-tight, and aesthetically attractive. The barrier garment apparatus can be, for example, a device, a panty, a boyshort, a short, a lingerie item, a barrier, a garment, an undergarment, a membrane, a prophylactic, and/or a system.
