Condoms are made of latex, and are one of the most effective tools in preventing STDs and unwanted pregnancies. If either of you has a latex allergy, use polyurethane condoms instead. Keep condoms away from heat and light, which can make them more likely to break. Only use water-based lubricants with condoms. Safe sex is very important especially if you are sexually active and a condom prevents the exchange of semen, vaginal fluids or blood between partners.