The Orgasm Flu by Andrew Daniels, of Men's Health

What if having sex literally made you sick?

It’s a nightmare scenario for most guys to even imagine, but for a handful of men across the world, it’s a crippling reality. Immediately after ejaculating, these men experience flu-like symptoms including a fever, runny nose, apathy, joint stiffness, and loss of short-term memory. Researchers have dubbed it “post-orgasmic illness syndrome” (POIS), and it’s as horrible as it sounds.

Jason*, a 31-year-old software engineer from Colorado, has suffered from POIS since he first hit puberty. Whether it’s through sex, masturbation, or even nocturnal emission, Jason’s symptoms kick in for 20 minutes after he ejaculates—and typically last up to 2 weeks. Because the pain is often so intense, it’s effectively killed his sex life.

“It’s gotten to the point where I will not have sex or ejaculate,” he says. “As a result, I’ve been abstinent for about a year now.”

Once thought to be a psychological illness, research from the Netherlands recently suggested that POIS may be caused by an allergy to semen. A Utretcht University team studied 33 Dutch men who reported POIS symptoms by giving them skin-prick tests using a diluted form of their own semen. Eighty-eight percent of the men tested positive for the allergy.

In a follow-up study, researchers injected two of the men with increasing amounts of their own semen so they could gradually build tolerance to the allergy. (It’s sort of like how allergists desensitize people to pollen, only with, you know, semen.) Sure enough, after 3 years, both men saw significant reductions in their symptoms.

But some experts are skeptical that allergies are to blame. In fact, David Resnick, M.D., director of allergy at New York-Presbyterian Hospital Columbia, says the notion of men being allergic to their own semen is almost impossible.

“If they were allergic, they’d have a reaction when they produced it internally, too. That’s why I find it hard to believe,” says Resnick. While women can be allergic to men’s semen—their bodies recognize semen as a foreign protein, in a condition known as seminal plasma hypersensitivity—Resnick says the same allergy would make no sense in a man. “If a man produces his semen, he would already have an allergic reaction to his own prostate.”

So what’s causing the “allergic reactions”? Jonathan Bernstein, M.D., a professor of medicine at the University of Cincinnati, has seen men react to positive skin tests for their seminal fluid, but says that doesn’t necessarily mean an allergy is to blame. “The reaction could be more of an irritation to the fluid, and not an immunologic response.”

Because POIS is relatively new—it’s only been documented in medical journals since 2002—and very uncommon (researchers estimate that it affects less than one percent of the population), treatment in America is limited.

Jason lives a relatively normal life—his girlfriend understands his issues and is okay with not having sex. Though he’s managed to accept his celibacy, it certainly hasn’t come easy. “You know how guys are, especially when we’re young. In our early 20s, we want to have sex often, and if we wait two weeks, that’s a long time! But if you have POIS and have sex frequently, you always have these horrible symptoms. You feel horrible when you have POIS, and the only way to feel better is to have sex. It’s a vicious cycle like a drug user would have.”

So how does he deal with his celibate life? “You need to meet the right person for a meaningful relationship—someone who doesn’t need sex, who’s understanding and patient. To maintain the relationship without sex, you need to do the small things like spending quality time with your partner, doing kind gestures, and giving small gifts to show you appreciate her. Really go above and beyond. You can still have the physical connection . . . just not a sexual one.”

If you suffer from POIS symptoms and feel shame and anxiety because of it, Men’s Health sex advisor Debby Herbenick, M.P.H., Ph.D., suggests seeking a sex therapist through the Society for Sex Therapy and Research (sstarnet.org).