Allergic reactions to semen are, unfortunately, very real.

In an essay for The Conversation, reproductive science specialist Michael Carroll of the UK’s Manchester Metropolitan University explained that allergic reactions to seminal fluid can manifest as a nasty response to a partner’s ejaculate, or even your own.

The most common semen allergy is what’s known as “seminal plasma hypersensitivity” or SPH, in which women who have sex with men react to proteins in seminal plasma, the goopy stuff that makes up spunk. In other words, it’s the seminal fluid that’s to blame, not the sperm itself — but the symptoms are very real, ranging from irritating vulvar itching and painful vaginal burning to anaphylactic shock.

Bottom line? A lot of people might be suffering from this and not even know it. If you might be, doctors recommend either using condoms, taking antihistamines before sex, taking anti-inflammatory medications after sex, or desensitization therapy involving exposure of diluted semen to the skin.

“If sex routinely leaves you itchy, sore or unwell — and condoms help — you might be allergic to semen,” Carroll wrote.

First documented nearly 60 years ago when a woman had to be hospitalized for her “violent allergic reaction” to sex, SPH is still, the reproductive expert wrote, often underdiagnosed. Until the year 1997, the medical establishment thought that fewer than 100 women had ever experienced the allergy, but a seminal — sorry — study that year found that nearly 12 percent of postcoital illnesses could be attributed to SPH. (Regrettably, there does not appear to be any formal inquiry whether men who have sex with men can have SPH, though there does appear to be anecdotal evidence that it does.)

About 15 years later, Carroll conducted an informal survey that found the same rate of probable SPH, though he found that the cases had often gone misdiagnosed as sexually transmitted illnesses, yeast infections, or even run-of-the-mill “sensitivity.” Given that its symptoms mirror some of those illnesses, it’s not hard to see why.

Along with being allergic to one’s partner’s semen, a separate condition known post-orgasmic illness syndrome (POIS) affects men who are allergic to their own skeet. With only 465 documented cases as of 2024, POIS can cause flu-like symptoms like fatigue and muscle aches immediately after ejaculation — and doctors are stumped as to its cause. Like SPH, both antihistamines and desensitization are recommended for POIS, as is hormonal therapy.

Speaking about SPH specifically, Carroll noted that more often than not, “sex-related symptoms often go unspoken.”

“Embarrassment, stigma, and a lack of awareness among doctors mean that many women suffer in silence,” the reproductive scientist said.

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