The risks: herpes (genital and oral), human papillomavirus (HPV), syphilis, gonorrhea
Cunnilingus is considered a low-risk behavior compared with vaginal or anal intercourse, but it's not completely risk-free. "You're not likely to get exposed to gonorrhea or chlamydia, because the person is not near the cervix where these infections reside," says Jeanne Marrazzo, MD, an infectious disease specialist at the University of Washington in Seattle. "But the partner performing the oral sex is at risk for STDs that can be on the skin or lining of the vagina like herpes simplex virus, HPV, or syphilis."
Dr. Marrazzo says that the receptive partner can even catch HSV-1 (the usual cause of cold sores) in the genital area because of oral sex.
And HIV? "While there is no data on cunnilingus causing HIV infection," she says, "I don't think anyone is comfortable saying that you can or cannot get it from oral sex."
How to reduce risk
Barrier methods, such as condoms or dental dams, are believed to be very effective at reducing risk, but some can really cut down on sensation. "Some women prefer to use plastic wrap to cover the area and maintain sensitivity," says Dr. Marrazzo. "In a pinch, some will cut a male condom down the middle to create a sheet of latex."
Also ensure that your mouth is in good health. Avoid oral sex if you have cuts, bleeding gums, or open sores in or around the mouth, as they can greatly increase your risk of catching a sexually transmitted disease.