A condom is a sheath-shaped barrier device used during sexual intercourse to reduce the probability of pregnancy or a sexually transmitted infection (STI).^[1][5] There are both external condoms, also called male condoms, and internal (female) condoms.^[6][7]

The external condom is rolled onto an erect penis before intercourse and works by forming a physical barrier which limits skin-to-skin contact, exposure to fluids, and blocks semen from entering the body of a sexual partner.^[1][8] External condoms are typically made from latex and, less commonly, from polyurethane, polyisoprene, or lamb intestine.^[1] External condoms have the advantages of ease of use, ease of access, and few side effects.^[1] Individuals with latex allergy should use condoms made from a material other than latex, such as polyurethane.^[1] Internal condoms are typically made from polyurethane and may be used multiple times.^[8]

With proper use—and use at every act of intercourse—women whose partners use external condoms experience a 2% per-year pregnancy rate.^[1] With typical use, the rate of pregnancy is 18% per-year.^[4] Their use greatly decreases the risk of gonorrhea, chlamydia, trichomoniasis, hepatitis B, and HIV/AIDS.^[1] To a lesser extent, they also protect against genital herpes, human papillomavirus (HPV), and syphilis.^[1]