To prevent getting a sexually transmitted disease, or STD, always avoid sex with anyone who has genital sores, a rash, discharge, or other symptoms. The only time unprotected sex is safe is if you and your partner have sex only with each other, and if it's been at least six months since you each tested negative for STDs. Otherwise you should: Use latex condoms every time you have sex. If you use a lubricant, make sure it's water-based. Use condoms for the entire sex act. Condoms are not 100% effective at preventing disease or pregnancy. However, they are extremely effective if used properly. Learn how to use condoms correctly.Avoid sharing towels or...