Every year there are more than 15 million new cases of STDs in the United States, including approximately 10 million new cases among people aged 15-24. Put another way--by age 24, at least one in three sexually active people will have contracted an STD. And many of those who are infected don't know it.
You can't tell if someone has an STD by the way he or she looks or acts. That wholesome-looking guy or woman may look safe and seem safe, but appearances can be deceiving. After all, you're not just having sex with that person but with everyone they've ever had sex with . . . and everyone THEY'VE ever had sex with . . . and . . . well, you get the point. Because lots of STDs have no symptoms (or only subtle ones), your partner may not even know he or she has one. That's why if you have ever had sex , you should get tested for STDs like chlamydia and HIV, even if you have no symptoms and are feeling just fine.
To be blunt about it: the only way to be sure you're having safer sex is to keep your partner's blood, semen, or vaginal fluids out of your body. Abstinence is the safest course. But, if you're going to have sex, always use condoms and dental dams (square pieces of latex available in some drugstores) for oral sex.
