Can Swallowing Semen Cause Stomach Problems?

The Situation: Your friend loves sex—but she's not exactly tied down to one guy, and even when she is, one fact remains constant: She loves giving oral, and she always swallows. No shame in that, you think—to each her own. But what about all that man juice? The Reality: Semen is made up of the same harmless nutrients, minerals, and sugars that you probably eat every day—stuff like vitamin C, potassium, calcium, and fructose. (Sperm cells actually account for a very small portion of semen.) Still, it can't replace your peanut butter protein shake: A man only produces about a teaspoon of semen per orgasm, and that's not nearly enough to provide any health benefits—even if you're getting it daily. But it also doesn't contain any seriously foreign ingredients, and your body digests it like any other sustenance you eat, says Debby Herbenick, an associate professor at Indiana University School of Public Health. The real danger lies in the risk of infection before you swallow.

The Worst That Can Happen: You could contract a sexually transmitted infection. But that's regardless of whether you swallow or not, Herbenick says. With oral sex, as soon as your mouth comes into contact with the penis, you could contract STIs transmissible via skin-to-skin contact—like oral and genital herpes, human papilloma virus (HPV), and syphilis. If any ejaculation occurs, that puts you at risk of contracting STIs like chlamydia, gonorrhea, and HIV, which can be transmitted by bodily fluids like saliva, vaginal secretions, and semen. "Any ejaculation in the mouth certainly raises the risk of STI transmission, but even just regular old oral sex carries risk due to pre-ejaculate and the fact that some people ejaculate without warning," Herbenick says. That means you're at risk of contracting those STIs even if he never fully ejaculates in your mouth. In your friend's case, oral sex ends with swallowing, but there's little risk in that—if you've gotten that far, the potential damage has already been done.

What'll Probably Happen: "The vast majority of the time people swallow semen, nothing happens," Herbenick says. Some people do report stomachaches and diarrhea shortly after swallowing, but that's rare and the research isn't well understood, she adds. Though various studies suggest that semen has antidepressant properties or reduces the risk of preeclampsia—a dangerous hypertensive complication during pregnancy—the research looked at vaginal contact and the findings are inconclusive.

What You Should Tell Your Friend: If you're in a mutually monogamous relationship, and you're sure your partner is STI-free, having unprotected oral sex and swallowing his semen won't pose any serious risks beyond, possibly, a temporary stomachache. Going unprotected without knowing if the guy's clean? Ideally, then, you'd use a condom every time your mouth goes south—that's the safest route, but it's also relatively uncommon, Herbenick says. Bottom line: Get tested and stay informed about your sexual health status, and your partner's (or…partners'). That means getting tested for STIs as often as your healthcare provider recommends, Herbenick says, especially if you're sexually active with a new partner or in an open relationship.

Read This Next: Mouth Wash Can Kill STDs