A condom is a sheath-shaped barrier device used during sexual intercourse to reduce the probability of pregnancy or a sexually transmitted infection (STI). There are both external condoms, also called male condoms, and internal (female) condoms.
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. External condoms are typically made from latex and, less commonly, from polyurethane, polyisoprene, or lamb intestine. External condoms have the advantages of ease of use, ease of access, and few side effects. Individuals with latex allergy should use condoms made from a material other than latex, such as polyurethane. Internal condoms are typically made from polyurethane and may be used multiple times.